diff --git a/tests/AlgebraTest.php b/tests/AlgebraTest.php
index e3ec6254a..24d96e9e2 100644
--- a/tests/AlgebraTest.php
+++ b/tests/AlgebraTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PhpParser;
diff --git a/tests/AnnotationTest.php b/tests/AnnotationTest.php
index b06bd217e..765dcaca8 100644
--- a/tests/AnnotationTest.php
+++ b/tests/AnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/ArgTest.php b/tests/ArgTest.php
index 9cb3753b6..adc03ac5e 100644
--- a/tests/ArgTest.php
+++ b/tests/ArgTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index 2302b2661..28ee56f74 100644
--- a/tests/ArrayAccessTest.php
+++ b/tests/ArrayAccessTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/ArrayAssignmentTest.php b/tests/ArrayAssignmentTest.php
index 11f308676..91a319f2f 100644
--- a/tests/ArrayAssignmentTest.php
+++ b/tests/ArrayAssignmentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/ArrayFunctionCallTest.php b/tests/ArrayFunctionCallTest.php
index fc13113e9..d8091ccb1 100644
--- a/tests/ArrayFunctionCallTest.php
+++ b/tests/ArrayFunctionCallTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/AssertAnnotationTest.php b/tests/AssertAnnotationTest.php
index 5b619971f..329a770dc 100644
--- a/tests/AssertAnnotationTest.php
+++ b/tests/AssertAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/AssignmentTest.php b/tests/AssignmentTest.php
index a85a4c2bc..210624210 100644
--- a/tests/AssignmentTest.php
+++ b/tests/AssignmentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/AsyncTestCase.php b/tests/AsyncTestCase.php
index f7fb5b30c..0e89d7659 100644
--- a/tests/AsyncTestCase.php
+++ b/tests/AsyncTestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Amp\PHPUnit\AsyncTestCase as BaseAsyncTestCase;
diff --git a/tests/AttributeTest.php b/tests/AttributeTest.php
index 18d82b04e..1603c7d84 100644
--- a/tests/AttributeTest.php
+++ b/tests/AttributeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/BadFormatTest.php b/tests/BadFormatTest.php
index 9aaf55873..88c59f242 100644
--- a/tests/BadFormatTest.php
+++ b/tests/BadFormatTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/BinaryOperationTest.php b/tests/BinaryOperationTest.php
index f0fe0c9e3..094f1bbe0 100644
--- a/tests/BinaryOperationTest.php
+++ b/tests/BinaryOperationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/ByIssueLevelAndTypeReportTest.php b/tests/ByIssueLevelAndTypeReportTest.php
index 2b8eb7a55..930d0dad6 100644
--- a/tests/ByIssueLevelAndTypeReportTest.php
+++ b/tests/ByIssueLevelAndTypeReportTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PHPUnit\Framework\TestCase;
diff --git a/tests/Cache/CacheTest.php b/tests/Cache/CacheTest.php
index 0efce1c68..cc81d4a60 100644
--- a/tests/Cache/CacheTest.php
+++ b/tests/Cache/CacheTest.php
@@ -65,7 +65,7 @@ class CacheTest extends TestCase
      * @dataProvider provideCacheInteractions
      */
     public function testCacheInteractions(
-        array $interactions
+        array $interactions,
     ): void {
         $config = Config::loadFromXML(
             __DIR__ . DIRECTORY_SEPARATOR . 'test_base_dir',
diff --git a/tests/CallableTest.php b/tests/CallableTest.php
index a6c4f421f..ffdc5ba55 100644
--- a/tests/CallableTest.php
+++ b/tests/CallableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/CastTest.php b/tests/CastTest.php
index fe93e5d7b..00d1eae45 100644
--- a/tests/CastTest.php
+++ b/tests/CastTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
diff --git a/tests/CheckTypeTest.php b/tests/CheckTypeTest.php
index a3f0aabbf..bfd3f3948 100644
--- a/tests/CheckTypeTest.php
+++ b/tests/CheckTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ClassLikeDocblockParserTest.php b/tests/ClassLikeDocblockParserTest.php
index 96a0f6911..f71754ef0 100644
--- a/tests/ClassLikeDocblockParserTest.php
+++ b/tests/ClassLikeDocblockParserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PhpParser\Comment\Doc;
diff --git a/tests/ClassLikeStringTest.php b/tests/ClassLikeStringTest.php
index b3bcca561..acd1ef96b 100644
--- a/tests/ClassLikeStringTest.php
+++ b/tests/ClassLikeStringTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/ClassLoadOrderTest.php b/tests/ClassLoadOrderTest.php
index 9d8f36c38..31c4742e0 100644
--- a/tests/ClassLoadOrderTest.php
+++ b/tests/ClassLoadOrderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ClassScopeTest.php b/tests/ClassScopeTest.php
index ca4565c54..67de84622 100644
--- a/tests/ClassScopeTest.php
+++ b/tests/ClassScopeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ClassTest.php b/tests/ClassTest.php
index a56451303..6f9c6682b 100644
--- a/tests/ClassTest.php
+++ b/tests/ClassTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ClosureTest.php b/tests/ClosureTest.php
index 43fff6bb0..61ae873cd 100644
--- a/tests/ClosureTest.php
+++ b/tests/ClosureTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/CodebaseTest.php b/tests/CodebaseTest.php
index 81e7a7786..0a1764307 100644
--- a/tests/CodebaseTest.php
+++ b/tests/CodebaseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PhpParser\Node\Name;
diff --git a/tests/CommentAnalyzerTest.php b/tests/CommentAnalyzerTest.php
index a3ddcc55d..c663d27f5 100644
--- a/tests/CommentAnalyzerTest.php
+++ b/tests/CommentAnalyzerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PHPUnit\Framework\TestCase as BaseTestCase;
diff --git a/tests/ComposerLockTest.php b/tests/ComposerLockTest.php
index a17225c6a..8f34d28f3 100644
--- a/tests/ComposerLockTest.php
+++ b/tests/ComposerLockTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Internal\PluginManager\ComposerLock;
@@ -212,10 +214,9 @@ class ComposerLockTest extends TestCase
     }
 
     /**
-     * @param mixed $data
      * @psalm-pure
      */
-    private function jsonFile($data): string
+    private function jsonFile(mixed $data): string
     {
         return 'data:application/json,' . json_encode($data, JSON_THROW_ON_ERROR);
     }
diff --git a/tests/Config/ConfigFileTest.php b/tests/Config/ConfigFileTest.php
index 1a58495b7..4408b7296 100644
--- a/tests/Config/ConfigFileTest.php
+++ b/tests/Config/ConfigFileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config;
 
 use Psalm\Config;
diff --git a/tests/Config/ConfigTest.php b/tests/Config/ConfigTest.php
index c664bd71a..9fa8042c5 100644
--- a/tests/Config/ConfigTest.php
+++ b/tests/Config/ConfigTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config;
 
 use Composer\Autoload\ClassLoader;
diff --git a/tests/Config/CreatorTest.php b/tests/Config/CreatorTest.php
index 38015e8df..2928e417c 100644
--- a/tests/Config/CreatorTest.php
+++ b/tests/Config/CreatorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config;
 
 use Psalm\Config\Creator;
diff --git a/tests/Config/Plugin/AfterAnalysisPlugin.php b/tests/Config/Plugin/AfterAnalysisPlugin.php
index 886ef8fe0..fed6ef87b 100644
--- a/tests/Config/Plugin/AfterAnalysisPlugin.php
+++ b/tests/Config/Plugin/AfterAnalysisPlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin;
 
 use Psalm\Plugin\PluginEntryPointInterface;
diff --git a/tests/Config/Plugin/FilePlugin.php b/tests/Config/Plugin/FilePlugin.php
index b32c067b2..4fbfb51e1 100644
--- a/tests/Config/Plugin/FilePlugin.php
+++ b/tests/Config/Plugin/FilePlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin;
 
 use Psalm\Plugin\PluginEntryPointInterface;
diff --git a/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php b/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php
index 2996de324..e9df94336 100644
--- a/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php
+++ b/tests/Config/Plugin/FileTypeSelfRegisteringPlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config\Plugin;
 
 use Psalm\Plugin\FileExtensionsInterface;
diff --git a/tests/Config/Plugin/FunctionPlugin.php b/tests/Config/Plugin/FunctionPlugin.php
index b17575bda..53746b73e 100644
--- a/tests/Config/Plugin/FunctionPlugin.php
+++ b/tests/Config/Plugin/FunctionPlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin;
 
 use Psalm\Plugin\PluginEntryPointInterface;
diff --git a/tests/Config/Plugin/Hook/AfterAnalysis.php b/tests/Config/Plugin/Hook/AfterAnalysis.php
index d7fff9b76..5d9be05bb 100644
--- a/tests/Config/Plugin/Hook/AfterAnalysis.php
+++ b/tests/Config/Plugin/Hook/AfterAnalysis.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin\Hook;
 
 use Psalm\Plugin\EventHandler\AfterAnalysisInterface;
diff --git a/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php b/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
index a491d9ecf..fb2853f35 100644
--- a/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
+++ b/tests/Config/Plugin/Hook/CustomArrayMapFunctionStorageProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config\Plugin\Hook;
 
 use Psalm\Codebase;
@@ -108,7 +110,7 @@ class CustomArrayMapFunctionStorageProvider implements DynamicFunctionStoragePro
     private static function createExpectedCallable(
         Union $input_type,
         DynamicTemplateProvider $template_provider,
-        int $return_template_offset = 0
+        int $return_template_offset = 0,
     ): TCallable {
         return new TCallable(
             'callable',
@@ -124,7 +126,7 @@ class CustomArrayMapFunctionStorageProvider implements DynamicFunctionStoragePro
      */
     private static function createRestCallables(
         DynamicTemplateProvider $template_provider,
-        int $expected_callable_args_count
+        int $expected_callable_args_count,
     ): array {
         $rest_callable_params = [];
 
@@ -160,7 +162,7 @@ class CustomArrayMapFunctionStorageProvider implements DynamicFunctionStoragePro
      */
     private static function createTemplates(
         DynamicTemplateProvider $template_provider,
-        int $expected_callable_count
+        int $expected_callable_count,
     ): array {
         $template_params = [];
 
diff --git a/tests/Config/Plugin/Hook/FileProvider.php b/tests/Config/Plugin/Hook/FileProvider.php
index 794b34c16..b6835a425 100644
--- a/tests/Config/Plugin/Hook/FileProvider.php
+++ b/tests/Config/Plugin/Hook/FileProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin\Hook;
 
 use Psalm\Plugin\EventHandler\AfterFileAnalysisInterface;
diff --git a/tests/Config/Plugin/Hook/FooMethodProvider.php b/tests/Config/Plugin/Hook/FooMethodProvider.php
index b5d150e03..c8ee5ef3d 100644
--- a/tests/Config/Plugin/Hook/FooMethodProvider.php
+++ b/tests/Config/Plugin/Hook/FooMethodProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin\Hook;
 
 use Psalm\Plugin\EventHandler\Event\MethodExistenceProviderEvent;
diff --git a/tests/Config/Plugin/Hook/FooPropertyProvider.php b/tests/Config/Plugin/Hook/FooPropertyProvider.php
index 7b7e3e36d..cef5a56dd 100644
--- a/tests/Config/Plugin/Hook/FooPropertyProvider.php
+++ b/tests/Config/Plugin/Hook/FooPropertyProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin\Hook;
 
 use Psalm\Plugin\EventHandler\Event\PropertyExistenceProviderEvent;
diff --git a/tests/Config/Plugin/Hook/MagicFunctionProvider.php b/tests/Config/Plugin/Hook/MagicFunctionProvider.php
index 9ffa3706c..8dd5e926e 100644
--- a/tests/Config/Plugin/Hook/MagicFunctionProvider.php
+++ b/tests/Config/Plugin/Hook/MagicFunctionProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin\Hook;
 
 use Psalm\Plugin\EventHandler\Event\FunctionExistenceProviderEvent;
diff --git a/tests/Config/Plugin/MethodPlugin.php b/tests/Config/Plugin/MethodPlugin.php
index d328165ef..a8fbefc36 100644
--- a/tests/Config/Plugin/MethodPlugin.php
+++ b/tests/Config/Plugin/MethodPlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin;
 
 use Psalm\Plugin\PluginEntryPointInterface;
diff --git a/tests/Config/Plugin/PropertyPlugin.php b/tests/Config/Plugin/PropertyPlugin.php
index 409cabbaf..1870a7ed4 100644
--- a/tests/Config/Plugin/PropertyPlugin.php
+++ b/tests/Config/Plugin/PropertyPlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Test\Config\Plugin;
 
 use Psalm\Plugin\PluginEntryPointInterface;
diff --git a/tests/Config/Plugin/StoragePlugin.php b/tests/Config/Plugin/StoragePlugin.php
index d59674867..482d95781 100644
--- a/tests/Config/Plugin/StoragePlugin.php
+++ b/tests/Config/Plugin/StoragePlugin.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config\Plugin;
 
 use Psalm\Plugin\PluginEntryPointInterface;
diff --git a/tests/Config/PluginListTest.php b/tests/Config/PluginListTest.php
index e10e482af..5ca98ab0e 100644
--- a/tests/Config/PluginListTest.php
+++ b/tests/Config/PluginListTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config;
 
 use InvalidArgumentException;
@@ -18,14 +20,11 @@ class PluginListTest extends TestCase
 {
     use MockeryPHPUnitIntegration;
 
-    /** @var ConfigFile&MockInterface */
-    private $config_file;
+    private ConfigFile&MockInterface $config_file;
 
-    /** @var Config&MockInterface */
-    private $config;
+    private Config&MockInterface $config;
 
-    /** @var ComposerLock&MockInterface */
-    private $composer_lock;
+    private ComposerLock&MockInterface $composer_lock;
 
     public function setUp(): void
     {
diff --git a/tests/Config/PluginTest.php b/tests/Config/PluginTest.php
index 57d759e67..93f2eb95b 100644
--- a/tests/Config/PluginTest.php
+++ b/tests/Config/PluginTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Config;
 
 use InvalidArgumentException;
diff --git a/tests/ConstValuesTest.php b/tests/ConstValuesTest.php
index 7ff3c51f7..564867fda 100644
--- a/tests/ConstValuesTest.php
+++ b/tests/ConstValuesTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ConstantTest.php b/tests/ConstantTest.php
index 785dbf4f0..bc0ec6404 100644
--- a/tests/ConstantTest.php
+++ b/tests/ConstantTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/CoreStubsTest.php b/tests/CoreStubsTest.php
index ed3d0b763..87f26f859 100644
--- a/tests/CoreStubsTest.php
+++ b/tests/CoreStubsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/DateTimeTest.php b/tests/DateTimeTest.php
index d8c608820..7a6d955d4 100644
--- a/tests/DateTimeTest.php
+++ b/tests/DateTimeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Exception;
diff --git a/tests/DeprecatedAnnotationTest.php b/tests/DeprecatedAnnotationTest.php
index adcf30e5b..aa3a169cf 100644
--- a/tests/DeprecatedAnnotationTest.php
+++ b/tests/DeprecatedAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/DocCommentTest.php b/tests/DocCommentTest.php
index 487b7c69a..03e64caf9 100644
--- a/tests/DocCommentTest.php
+++ b/tests/DocCommentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PHPUnit\Framework\TestCase as BaseTestCase;
diff --git a/tests/DocblockInheritanceTest.php b/tests/DocblockInheritanceTest.php
index 3a09ad9a3..792c7972b 100644
--- a/tests/DocblockInheritanceTest.php
+++ b/tests/DocblockInheritanceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/DocumentationTest.php b/tests/DocumentationTest.php
index 599e7af32..9768eecfa 100644
--- a/tests/DocumentationTest.php
+++ b/tests/DocumentationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use DOMAttr;
@@ -409,18 +411,12 @@ class DocumentationTest extends TestCase
                 return $this->inner->toString();
             }
 
-            /**
-             * @param mixed $other
-             */
-            protected function matches($other): bool
+            protected function matches(mixed $other): bool
             {
                 return $this->inner->matches($other);
             }
 
-            /**
-             * @param mixed $other
-             */
-            protected function failureDescription($other): string
+            protected function failureDescription(mixed $other): string
             {
                 return $this->exporter()->shortenedExport($other) . ' ' . $this->toString();
             }
diff --git a/tests/EndToEnd/DestructiveAutoloaderTest.php b/tests/EndToEnd/DestructiveAutoloaderTest.php
index 400efeec9..74a8a59e6 100644
--- a/tests/EndToEnd/DestructiveAutoloaderTest.php
+++ b/tests/EndToEnd/DestructiveAutoloaderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\EndToEnd;
 
 use PHPUnit\Framework\TestCase;
diff --git a/tests/EndToEnd/PsalmEndToEndTest.php b/tests/EndToEnd/PsalmEndToEndTest.php
index 2a9cff2bf..cf6ceca8c 100644
--- a/tests/EndToEnd/PsalmEndToEndTest.php
+++ b/tests/EndToEnd/PsalmEndToEndTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\EndToEnd;
 
 use Exception;
diff --git a/tests/EndToEnd/PsalmRunnerTrait.php b/tests/EndToEnd/PsalmRunnerTrait.php
index 03e7f714e..33d82e7c7 100644
--- a/tests/EndToEnd/PsalmRunnerTrait.php
+++ b/tests/EndToEnd/PsalmRunnerTrait.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\EndToEnd;
 
 use Symfony\Component\Process\Process;
@@ -22,7 +24,7 @@ trait PsalmRunnerTrait
         array $args,
         string $workingDir,
         bool $shouldFail = false,
-        bool $relyOnConfigDir = true
+        bool $relyOnConfigDir = true,
     ): array {
         // Ensure CI agnostic output
         if (!in_array('--init', $args, true) && !in_array('--alter', $args, true)) {
diff --git a/tests/EndToEnd/SuicidalAutoloaderTest.php b/tests/EndToEnd/SuicidalAutoloaderTest.php
index 0aaf3b511..722520fe0 100644
--- a/tests/EndToEnd/SuicidalAutoloaderTest.php
+++ b/tests/EndToEnd/SuicidalAutoloaderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\EndToEnd;
 
 use PHPUnit\Framework\TestCase;
diff --git a/tests/EnumTest.php b/tests/EnumTest.php
index 83fd1cf75..354911c88 100644
--- a/tests/EnumTest.php
+++ b/tests/EnumTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ErrorBaselineTest.php b/tests/ErrorBaselineTest.php
index 6a9278297..584748d41 100644
--- a/tests/ErrorBaselineTest.php
+++ b/tests/ErrorBaselineTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use DOMDocument;
@@ -21,8 +23,7 @@ class ErrorBaselineTest extends TestCase
 {
     use MockeryPHPUnitIntegration;
 
-    /** @var FileProvider&MockInterface */
-    private $fileProvider;
+    private FileProvider&MockInterface $fileProvider;
 
     public function setUp(): void
     {
diff --git a/tests/ExpressionTest.php b/tests/ExpressionTest.php
index 57186daf9..15fb517c1 100644
--- a/tests/ExpressionTest.php
+++ b/tests/ExpressionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ExtendsFinalClassTest.php b/tests/ExtendsFinalClassTest.php
index c2f182887..229d7c51a 100644
--- a/tests/ExtendsFinalClassTest.php
+++ b/tests/ExtendsFinalClassTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ExtensionRequirementTest.php b/tests/ExtensionRequirementTest.php
index 2478531ad..154a514c2 100644
--- a/tests/ExtensionRequirementTest.php
+++ b/tests/ExtensionRequirementTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/FileDiffTest.php b/tests/FileDiffTest.php
index acc84f404..0e7982552 100644
--- a/tests/FileDiffTest.php
+++ b/tests/FileDiffTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PhpParser;
@@ -27,7 +29,7 @@ class FileDiffTest extends TestCase
         array $same_signatures,
         array $changed_methods,
         array $diff_map_offsets,
-        array $deletion_ranges
+        array $deletion_ranges,
     ): void {
         if (strpos($this->getTestName(), 'SKIPPED-') !== false) {
             $this->markTestSkipped();
@@ -84,7 +86,7 @@ class FileDiffTest extends TestCase
         array $same_methods,
         array $same_signatures,
         array $changed_methods,
-        array $diff_map_offsets
+        array $diff_map_offsets,
     ): void {
         if (strpos($this->getTestName(), 'SKIPPED-') !== false) {
             $this->markTestSkipped();
diff --git a/tests/FileManipulation/ClassConstantMoveTest.php b/tests/FileManipulation/ClassConstantMoveTest.php
index f06239abb..3e22aa14a 100644
--- a/tests/FileManipulation/ClassConstantMoveTest.php
+++ b/tests/FileManipulation/ClassConstantMoveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 use Psalm\Context;
@@ -31,7 +33,7 @@ class ClassConstantMoveTest extends TestCase
     public function testValidCode(
         string $input_code,
         string $output_code,
-        array $constants_to_move
+        array $constants_to_move,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileManipulation/ClassMoveTest.php b/tests/FileManipulation/ClassMoveTest.php
index e49e0cf87..c2f5c8ee7 100644
--- a/tests/FileManipulation/ClassMoveTest.php
+++ b/tests/FileManipulation/ClassMoveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 use Psalm\Context;
@@ -31,7 +33,7 @@ class ClassMoveTest extends TestCase
     public function testValidCode(
         string $input_code,
         string $output_code,
-        array $constants_to_move
+        array $constants_to_move,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileManipulation/FileManipulationTestCase.php b/tests/FileManipulation/FileManipulationTestCase.php
index de361f6ff..069412838 100644
--- a/tests/FileManipulation/FileManipulationTestCase.php
+++ b/tests/FileManipulation/FileManipulationTestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 use Psalm\Context;
@@ -34,7 +36,7 @@ abstract class FileManipulationTestCase extends TestCase
         string $php_version,
         array $issues_to_fix,
         bool $safe_types,
-        bool $allow_backwards_incompatible_changes = true
+        bool $allow_backwards_incompatible_changes = true,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileManipulation/ImmutableAnnotationAdditionTest.php b/tests/FileManipulation/ImmutableAnnotationAdditionTest.php
index 926cef22a..0e3083911 100644
--- a/tests/FileManipulation/ImmutableAnnotationAdditionTest.php
+++ b/tests/FileManipulation/ImmutableAnnotationAdditionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class ImmutableAnnotationAdditionTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/MethodMoveTest.php b/tests/FileManipulation/MethodMoveTest.php
index 4e97bb863..51c9b18dc 100644
--- a/tests/FileManipulation/MethodMoveTest.php
+++ b/tests/FileManipulation/MethodMoveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 use Psalm\Context;
@@ -31,7 +33,7 @@ class MethodMoveTest extends TestCase
     public function testValidCode(
         string $input_code,
         string $output_code,
-        array $methods_to_move
+        array $methods_to_move,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileManipulation/MissingPropertyTypeTest.php b/tests/FileManipulation/MissingPropertyTypeTest.php
index afeb644ee..9fe744661 100644
--- a/tests/FileManipulation/MissingPropertyTypeTest.php
+++ b/tests/FileManipulation/MissingPropertyTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class MissingPropertyTypeTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/MissingReturnTypeTest.php b/tests/FileManipulation/MissingReturnTypeTest.php
index 4d43cd1a4..848398b2d 100644
--- a/tests/FileManipulation/MissingReturnTypeTest.php
+++ b/tests/FileManipulation/MissingReturnTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class MissingReturnTypeTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/NamespaceMoveTest.php b/tests/FileManipulation/NamespaceMoveTest.php
index 11920d2d6..537d20b83 100644
--- a/tests/FileManipulation/NamespaceMoveTest.php
+++ b/tests/FileManipulation/NamespaceMoveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 use Psalm\Context;
@@ -31,7 +33,7 @@ class NamespaceMoveTest extends TestCase
     public function testValidCode(
         string $input_code,
         string $output_code,
-        array $namespaces_to_move
+        array $namespaces_to_move,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileManipulation/ParamNameMismatchTest.php b/tests/FileManipulation/ParamNameMismatchTest.php
index 3dfd82d77..186885a43 100644
--- a/tests/FileManipulation/ParamNameMismatchTest.php
+++ b/tests/FileManipulation/ParamNameMismatchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class ParamNameMismatchTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/ParamTypeManipulationTest.php b/tests/FileManipulation/ParamTypeManipulationTest.php
index bf182d5c4..172a383d6 100644
--- a/tests/FileManipulation/ParamTypeManipulationTest.php
+++ b/tests/FileManipulation/ParamTypeManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class ParamTypeManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/PropertyMoveTest.php b/tests/FileManipulation/PropertyMoveTest.php
index b485cbb7c..5b0afa6dd 100644
--- a/tests/FileManipulation/PropertyMoveTest.php
+++ b/tests/FileManipulation/PropertyMoveTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 use Psalm\Context;
@@ -31,7 +33,7 @@ class PropertyMoveTest extends TestCase
     public function testValidCode(
         string $input_code,
         string $output_code,
-        array $properties_to_move
+        array $properties_to_move,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileManipulation/PureAnnotationAdditionTest.php b/tests/FileManipulation/PureAnnotationAdditionTest.php
index 3434481ad..2b44581a8 100644
--- a/tests/FileManipulation/PureAnnotationAdditionTest.php
+++ b/tests/FileManipulation/PureAnnotationAdditionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class PureAnnotationAdditionTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/RedundantCastManipulationTest.php b/tests/FileManipulation/RedundantCastManipulationTest.php
index fa679ce33..71342cb4a 100644
--- a/tests/FileManipulation/RedundantCastManipulationTest.php
+++ b/tests/FileManipulation/RedundantCastManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class RedundantCastManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/ReturnTypeManipulationTest.php b/tests/FileManipulation/ReturnTypeManipulationTest.php
index d4221eb1c..be9333c55 100644
--- a/tests/FileManipulation/ReturnTypeManipulationTest.php
+++ b/tests/FileManipulation/ReturnTypeManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class ReturnTypeManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/ThrowsBlockAdditionTest.php b/tests/FileManipulation/ThrowsBlockAdditionTest.php
index a4a2e8389..8111eef2b 100644
--- a/tests/FileManipulation/ThrowsBlockAdditionTest.php
+++ b/tests/FileManipulation/ThrowsBlockAdditionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class ThrowsBlockAdditionTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/UndefinedVariableManipulationTest.php b/tests/FileManipulation/UndefinedVariableManipulationTest.php
index 5d0e09eec..945e44630 100644
--- a/tests/FileManipulation/UndefinedVariableManipulationTest.php
+++ b/tests/FileManipulation/UndefinedVariableManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class UndefinedVariableManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php b/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php
index 99e3c22ae..95ca370bb 100644
--- a/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php
+++ b/tests/FileManipulation/UnnecessaryVarAnnotationManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class UnnecessaryVarAnnotationManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/UnusedCodeManipulationTest.php b/tests/FileManipulation/UnusedCodeManipulationTest.php
index efbc2c126..8dd8aaf89 100644
--- a/tests/FileManipulation/UnusedCodeManipulationTest.php
+++ b/tests/FileManipulation/UnusedCodeManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class UnusedCodeManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileManipulation/UnusedVariableManipulationTest.php b/tests/FileManipulation/UnusedVariableManipulationTest.php
index d41215421..dc1c65662 100644
--- a/tests/FileManipulation/UnusedVariableManipulationTest.php
+++ b/tests/FileManipulation/UnusedVariableManipulationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileManipulation;
 
 class UnusedVariableManipulationTest extends FileManipulationTestCase
diff --git a/tests/FileReferenceTest.php b/tests/FileReferenceTest.php
index a17172d86..770e96a2e 100644
--- a/tests/FileReferenceTest.php
+++ b/tests/FileReferenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
@@ -85,7 +87,7 @@ class FileReferenceTest extends TestCase
         array $expected_method_references_to_members,
         array $expected_method_references_to_missing_members,
         array $expected_file_references_to_members,
-        array $expected_file_references_to_missing_members
+        array $expected_file_references_to_missing_members,
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileUpdates/AnalyzedMethodTest.php b/tests/FileUpdates/AnalyzedMethodTest.php
index 30e8f29fa..598efeb61 100644
--- a/tests/FileUpdates/AnalyzedMethodTest.php
+++ b/tests/FileUpdates/AnalyzedMethodTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileUpdates;
 
 use Psalm\Config;
@@ -55,7 +57,7 @@ class AnalyzedMethodTest extends TestCase
         array $end_files,
         array $initial_analyzed_methods,
         array $unaffected_analyzed_methods,
-        array $ignored_issues = []
+        array $ignored_issues = [],
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'SKIPPED-') !== false) {
diff --git a/tests/FileUpdates/CachedStorageTest.php b/tests/FileUpdates/CachedStorageTest.php
index 3e6b97bff..a41a33b86 100644
--- a/tests/FileUpdates/CachedStorageTest.php
+++ b/tests/FileUpdates/CachedStorageTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileUpdates;
 
 use Psalm\Internal\Analyzer\ProjectAnalyzer;
diff --git a/tests/FileUpdates/ErrorAfterUpdateTest.php b/tests/FileUpdates/ErrorAfterUpdateTest.php
index 670ee34f4..162c71c1f 100644
--- a/tests/FileUpdates/ErrorAfterUpdateTest.php
+++ b/tests/FileUpdates/ErrorAfterUpdateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileUpdates;
 
 use Psalm\Exception\CodeException;
@@ -54,7 +56,7 @@ class ErrorAfterUpdateTest extends TestCase
     public function testErrorAfterUpdate(
         array $file_stages,
         string $error_message,
-        array $ignored_issues = []
+        array $ignored_issues = [],
     ): void {
         $this->project_analyzer->getCodebase()->diff_methods = true;
         $this->project_analyzer->getCodebase()->reportUnusedCode();
diff --git a/tests/FileUpdates/ErrorFixTest.php b/tests/FileUpdates/ErrorFixTest.php
index 7ea00bafe..c6e9ffc01 100644
--- a/tests/FileUpdates/ErrorFixTest.php
+++ b/tests/FileUpdates/ErrorFixTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileUpdates;
 
 use Psalm\Config;
@@ -55,7 +57,7 @@ class ErrorFixTest extends TestCase
     public function testErrorFix(
         array $files,
         array $error_counts,
-        array $ignored_issues = []
+        array $ignored_issues = [],
     ): void {
         $this->project_analyzer->getCodebase()->diff_methods = true;
 
diff --git a/tests/FileUpdates/TemporaryUpdateTest.php b/tests/FileUpdates/TemporaryUpdateTest.php
index f8e1c0bf0..507b483f0 100644
--- a/tests/FileUpdates/TemporaryUpdateTest.php
+++ b/tests/FileUpdates/TemporaryUpdateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\FileUpdates;
 
 use Psalm\Codebase;
@@ -71,7 +73,7 @@ class TemporaryUpdateTest extends TestCase
         array $error_positions,
         array $ignored_issues = [],
         bool $test_save = true,
-        bool $check_unused_code = false
+        bool $check_unused_code = false,
     ): void {
         $codebase = $this->codebase;
         $codebase->diff_methods = true;
diff --git a/tests/ForbiddenCodeTest.php b/tests/ForbiddenCodeTest.php
index 86b36f527..0a1911b16 100644
--- a/tests/ForbiddenCodeTest.php
+++ b/tests/ForbiddenCodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/FunctionCallTest.php b/tests/FunctionCallTest.php
index 23f9dcb08..23b4ae3bc 100644
--- a/tests/FunctionCallTest.php
+++ b/tests/FunctionCallTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/FunctionLikeDocblockParserTest.php b/tests/FunctionLikeDocblockParserTest.php
index 9574ba63e..07e38c915 100644
--- a/tests/FunctionLikeDocblockParserTest.php
+++ b/tests/FunctionLikeDocblockParserTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PHPUnit\Framework\TestCase as BaseTestCase;
diff --git a/tests/GeneratorTest.php b/tests/GeneratorTest.php
index d744e271a..350eabb50 100644
--- a/tests/GeneratorTest.php
+++ b/tests/GeneratorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/IfThisIsTest.php b/tests/IfThisIsTest.php
index 5b41fd7dd..1b8aeea2d 100644
--- a/tests/IfThisIsTest.php
+++ b/tests/IfThisIsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ImmutableAnnotationTest.php b/tests/ImmutableAnnotationTest.php
index 1aa481b2a..11e831393 100644
--- a/tests/ImmutableAnnotationTest.php
+++ b/tests/ImmutableAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ImplementationRequirementTest.php b/tests/ImplementationRequirementTest.php
index 83ab84a0a..a5ab34829 100644
--- a/tests/ImplementationRequirementTest.php
+++ b/tests/ImplementationRequirementTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/IncludeTest.php b/tests/IncludeTest.php
index e595260b8..6aa37c925 100644
--- a/tests/IncludeTest.php
+++ b/tests/IncludeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
@@ -24,7 +26,7 @@ class IncludeTest extends TestCase
         array $files,
         array $files_to_check,
         bool $hoist_constants = false,
-        array $ignored_issues = []
+        array $ignored_issues = [],
     ): void {
         $codebase = $this->project_analyzer->getCodebase();
 
@@ -64,7 +66,7 @@ class IncludeTest extends TestCase
         array $files,
         array $files_to_check,
         string $error_message,
-        array $directories = []
+        array $directories = [],
     ): void {
         if (strpos($this->getTestName(), 'SKIPPED-') !== false) {
             $this->markTestSkipped();
diff --git a/tests/IntRangeTest.php b/tests/IntRangeTest.php
index c7c09ae2d..852710db8 100644
--- a/tests/IntRangeTest.php
+++ b/tests/IntRangeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Internal\Type\TypeCombiner;
diff --git a/tests/InterfaceTest.php b/tests/InterfaceTest.php
index 91d56c16a..be5fec827 100644
--- a/tests/InterfaceTest.php
+++ b/tests/InterfaceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/Internal/CallMapTest.php b/tests/Internal/CallMapTest.php
index b6e843bb1..9bdb97c89 100644
--- a/tests/Internal/CallMapTest.php
+++ b/tests/Internal/CallMapTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal;
 
 use FilesystemIterator;
diff --git a/tests/Internal/CliUtilsTest.php b/tests/Internal/CliUtilsTest.php
index 0e00b7112..1f67fa508 100644
--- a/tests/Internal/CliUtilsTest.php
+++ b/tests/Internal/CliUtilsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal;
 
 use PHPUnit\Framework\TestCase;
diff --git a/tests/Internal/Codebase/InternalCallMapHandlerTest.php b/tests/Internal/Codebase/InternalCallMapHandlerTest.php
index 019c2484c..4740a1096 100644
--- a/tests/Internal/Codebase/InternalCallMapHandlerTest.php
+++ b/tests/Internal/Codebase/InternalCallMapHandlerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Codebase;
 
 use InvalidArgumentException;
diff --git a/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php b/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php
index 5af1cb945..096154de6 100644
--- a/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php
+++ b/tests/Internal/Provider/ClassLikeStorageInstanceCacheProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Provider;
 
 use Psalm\Internal\Provider\ClassLikeStorageCacheProvider;
diff --git a/tests/Internal/Provider/FakeFileReferenceCacheProvider.php b/tests/Internal/Provider/FakeFileReferenceCacheProvider.php
index 21544ff66..caa5e92ad 100644
--- a/tests/Internal/Provider/FakeFileReferenceCacheProvider.php
+++ b/tests/Internal/Provider/FakeFileReferenceCacheProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Provider;
 
 use Psalm\Config;
diff --git a/tests/Internal/Provider/FakeParserCacheProvider.php b/tests/Internal/Provider/FakeParserCacheProvider.php
index 36b1dbb3d..db5f8c6e8 100644
--- a/tests/Internal/Provider/FakeParserCacheProvider.php
+++ b/tests/Internal/Provider/FakeParserCacheProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Provider;
 
 use Psalm\Internal\Provider\ParserCacheProvider;
diff --git a/tests/Internal/Provider/FileStorageInstanceCacheProvider.php b/tests/Internal/Provider/FileStorageInstanceCacheProvider.php
index b6a732ae1..d32bc4e63 100644
--- a/tests/Internal/Provider/FileStorageInstanceCacheProvider.php
+++ b/tests/Internal/Provider/FileStorageInstanceCacheProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Provider;
 
 use Psalm\Internal\Provider\FileStorageCacheProvider;
diff --git a/tests/Internal/Provider/ParserInstanceCacheProvider.php b/tests/Internal/Provider/ParserInstanceCacheProvider.php
index 979e860ee..c227fec99 100644
--- a/tests/Internal/Provider/ParserInstanceCacheProvider.php
+++ b/tests/Internal/Provider/ParserInstanceCacheProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Provider;
 
 use PhpParser;
diff --git a/tests/Internal/Provider/ProjectCacheProvider.php b/tests/Internal/Provider/ProjectCacheProvider.php
index de162b842..a8ad1219b 100644
--- a/tests/Internal/Provider/ProjectCacheProvider.php
+++ b/tests/Internal/Provider/ProjectCacheProvider.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Provider;
 
 use Psalm\Internal\Provider\ProjectCacheProvider as PsalmProjectCacheProvider;
diff --git a/tests/Internal/Scanner/FileScannerTest.php b/tests/Internal/Scanner/FileScannerTest.php
index bb2b9ee91..588738fa0 100644
--- a/tests/Internal/Scanner/FileScannerTest.php
+++ b/tests/Internal/Scanner/FileScannerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Internal\Scanner;
 
 use Psalm\Aliases;
@@ -21,7 +23,7 @@ class FileScannerTest extends TestCase
     public function testScan(
         Config $config,
         string $file_contents,
-        FileStorage $expected_file_storage
+        FileStorage $expected_file_storage,
     ): void {
         $file_provider = new FakeFileProvider();
         $codebase = new Codebase(
diff --git a/tests/InternalAnnotationTest.php b/tests/InternalAnnotationTest.php
index 7d0341e8d..b4352f83b 100644
--- a/tests/InternalAnnotationTest.php
+++ b/tests/InternalAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/IssueBufferTest.php b/tests/IssueBufferTest.php
index 620052ba1..c3a3074e7 100644
--- a/tests/IssueBufferTest.php
+++ b/tests/IssueBufferTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Codebase;
diff --git a/tests/IssueSuppressionTest.php b/tests/IssueSuppressionTest.php
index 3fa40ae3d..3b703bb42 100644
--- a/tests/IssueSuppressionTest.php
+++ b/tests/IssueSuppressionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/JsonOutputTest.php b/tests/JsonOutputTest.php
index c20d7b9d7..09cc07289 100644
--- a/tests/JsonOutputTest.php
+++ b/tests/JsonOutputTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
@@ -49,7 +51,7 @@ class JsonOutputTest extends TestCase
         int $error_count,
         string $message,
         int $line_number,
-        string $error
+        string $error,
     ): void {
         $this->addFile('somefile.php', $code);
         $this->analyzeFile('somefile.php', new Context());
diff --git a/tests/LanguageServer/CompletionTest.php b/tests/LanguageServer/CompletionTest.php
index 942556f56..7e6cb52bd 100644
--- a/tests/LanguageServer/CompletionTest.php
+++ b/tests/LanguageServer/CompletionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\LanguageServer;
 
 use LanguageServerProtocol\Position;
diff --git a/tests/LanguageServer/DiagnosticTest.php b/tests/LanguageServer/DiagnosticTest.php
index 7648c7b55..29121fc6e 100644
--- a/tests/LanguageServer/DiagnosticTest.php
+++ b/tests/LanguageServer/DiagnosticTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\LanguageServer;
 
 use Amp\DeferredFuture;
diff --git a/tests/LanguageServer/FileMapTest.php b/tests/LanguageServer/FileMapTest.php
index e17b19be5..b89aa90a2 100644
--- a/tests/LanguageServer/FileMapTest.php
+++ b/tests/LanguageServer/FileMapTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\LanguageServer;
 
 use Psalm\Codebase;
diff --git a/tests/LanguageServer/Message.php b/tests/LanguageServer/Message.php
index 075a50a81..7ebbc6db0 100644
--- a/tests/LanguageServer/Message.php
+++ b/tests/LanguageServer/Message.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\LanguageServer;
 
 use AdvancedJsonRpc\Error;
diff --git a/tests/LanguageServer/PathMapperTest.php b/tests/LanguageServer/PathMapperTest.php
index 2e64b3563..eeed17d92 100644
--- a/tests/LanguageServer/PathMapperTest.php
+++ b/tests/LanguageServer/PathMapperTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\LanguageServer;
 
 use PHPUnit\Framework\TestCase;
@@ -37,7 +39,7 @@ final class PathMapperTest extends TestCase
         ?string $client_root_reconfigured,
         string $client_root_provided_later,
         string $client_path,
-        string $server_ath
+        string $server_ath,
     ): void {
         $mapper = new PathMapper($server_root, $client_root_reconfigured);
         $mapper->configureClientRoot($client_root_provided_later);
@@ -53,7 +55,7 @@ final class PathMapperTest extends TestCase
         ?string $client_root_preconfigured,
         string $client_root_provided_later,
         string $client_path,
-        string $server_path
+        string $server_path,
     ): void {
         $mapper = new PathMapper($server_root, $client_root_preconfigured);
         $mapper->configureClientRoot($client_root_provided_later);
diff --git a/tests/LanguageServer/SymbolLookupTest.php b/tests/LanguageServer/SymbolLookupTest.php
index d235bc334..a0a36cb5d 100644
--- a/tests/LanguageServer/SymbolLookupTest.php
+++ b/tests/LanguageServer/SymbolLookupTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\LanguageServer;
 
 use LanguageServerProtocol\Position;
@@ -626,7 +628,7 @@ class SymbolLookupTest extends TestCase
         Position $position,
         ?string $expected_symbol,
         ?int $expected_argument_number,
-        ?int $expected_param_count
+        ?int $expected_param_count,
     ): void {
         $config = $this->codebase->config;
         $config->throw_exception = false;
diff --git a/tests/ListTest.php b/tests/ListTest.php
index 5dce65e54..c36c4bac7 100644
--- a/tests/ListTest.php
+++ b/tests/ListTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/Loop/DoTest.php b/tests/Loop/DoTest.php
index 5c125de7f..536ff3567 100644
--- a/tests/Loop/DoTest.php
+++ b/tests/Loop/DoTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Loop;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Loop/ForTest.php b/tests/Loop/ForTest.php
index 4a868f2d0..f8fd5f2b2 100644
--- a/tests/Loop/ForTest.php
+++ b/tests/Loop/ForTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Loop;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Loop/ForeachTest.php b/tests/Loop/ForeachTest.php
index fbbb6e445..125be719e 100644
--- a/tests/Loop/ForeachTest.php
+++ b/tests/Loop/ForeachTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Loop;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Loop/WhileTest.php b/tests/Loop/WhileTest.php
index 73dd8085b..4976bac05 100644
--- a/tests/Loop/WhileTest.php
+++ b/tests/Loop/WhileTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Loop;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/MagicMethodAnnotationTest.php b/tests/MagicMethodAnnotationTest.php
index 6b7f05e32..ad157dad3 100644
--- a/tests/MagicMethodAnnotationTest.php
+++ b/tests/MagicMethodAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/MagicPropertyTest.php b/tests/MagicPropertyTest.php
index 27b5b36a5..d0e340719 100644
--- a/tests/MagicPropertyTest.php
+++ b/tests/MagicPropertyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/MatchTest.php b/tests/MatchTest.php
index e281a200e..ccab5ffef 100644
--- a/tests/MatchTest.php
+++ b/tests/MatchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/MethodCallTest.php b/tests/MethodCallTest.php
index 1f0019680..3a808c99f 100644
--- a/tests/MethodCallTest.php
+++ b/tests/MethodCallTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/MethodMutationTest.php b/tests/MethodMutationTest.php
index 7b4d103e8..921390683 100644
--- a/tests/MethodMutationTest.php
+++ b/tests/MethodMutationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/MethodSignatureTest.php b/tests/MethodSignatureTest.php
index 4c65719ee..e222ccf13 100644
--- a/tests/MethodSignatureTest.php
+++ b/tests/MethodSignatureTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/MixinAnnotationTest.php b/tests/MixinAnnotationTest.php
index 1769546aa..f4f0372cd 100644
--- a/tests/MixinAnnotationTest.php
+++ b/tests/MixinAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/NamespaceTest.php b/tests/NamespaceTest.php
index 60d989a22..3e1736214 100644
--- a/tests/NamespaceTest.php
+++ b/tests/NamespaceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/NativeIntersectionsTest.php b/tests/NativeIntersectionsTest.php
index 5d7c2a036..ade439a5f 100644
--- a/tests/NativeIntersectionsTest.php
+++ b/tests/NativeIntersectionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/NativeUnionsTest.php b/tests/NativeUnionsTest.php
index 3c0661818..0b7cc18ec 100644
--- a/tests/NativeUnionsTest.php
+++ b/tests/NativeUnionsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/Php40Test.php b/tests/Php40Test.php
index fa2a661ff..d9e274de6 100644
--- a/tests/Php40Test.php
+++ b/tests/Php40Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
diff --git a/tests/Php55Test.php b/tests/Php55Test.php
index fbfbc6e20..f2f9445da 100644
--- a/tests/Php55Test.php
+++ b/tests/Php55Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
diff --git a/tests/Php56Test.php b/tests/Php56Test.php
index 5dc67c79e..3f34b0c04 100644
--- a/tests/Php56Test.php
+++ b/tests/Php56Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
diff --git a/tests/Php70Test.php b/tests/Php70Test.php
index c8d31743d..4775ce779 100644
--- a/tests/Php70Test.php
+++ b/tests/Php70Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/Php71Test.php b/tests/Php71Test.php
index 4e8fe09f1..048debd21 100644
--- a/tests/Php71Test.php
+++ b/tests/Php71Test.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/Progress/EchoProgress.php b/tests/Progress/EchoProgress.php
index 7146bbf8a..11c77be93 100644
--- a/tests/Progress/EchoProgress.php
+++ b/tests/Progress/EchoProgress.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Progress;
 
 use Psalm\Progress\DefaultProgress;
diff --git a/tests/ProjectCheckerTest.php b/tests/ProjectCheckerTest.php
index cb155cf24..c2b07415b 100644
--- a/tests/ProjectCheckerTest.php
+++ b/tests/ProjectCheckerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/PropertiesOfTest.php b/tests/PropertiesOfTest.php
index 735629168..99a14e678 100644
--- a/tests/PropertiesOfTest.php
+++ b/tests/PropertiesOfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/PropertyTypeInvarianceTest.php b/tests/PropertyTypeInvarianceTest.php
index ba4b8a7b1..07fe43387 100644
--- a/tests/PropertyTypeInvarianceTest.php
+++ b/tests/PropertyTypeInvarianceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/PropertyTypeTest.php b/tests/PropertyTypeTest.php
index 0fbd78699..55b976fe0 100644
--- a/tests/PropertyTypeTest.php
+++ b/tests/PropertyTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use DateTime;
diff --git a/tests/PsalmPluginTest.php b/tests/PsalmPluginTest.php
index b6b2515d7..64311a301 100644
--- a/tests/PsalmPluginTest.php
+++ b/tests/PsalmPluginTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use InvalidArgumentException;
@@ -23,11 +25,9 @@ class PsalmPluginTest extends TestCase
 {
     use MockeryPHPUnitIntegration;
 
-    /** @var PluginList&MockInterface */
-    private $plugin_list;
+    private PluginList&MockInterface $plugin_list;
 
-    /** @var PluginListFactory&MockInterface */
-    private $plugin_list_factory;
+    private PluginListFactory&MockInterface $plugin_list_factory;
 
     private Application $app;
 
diff --git a/tests/PureAnnotationTest.php b/tests/PureAnnotationTest.php
index 7ea34d9ad..5ae7048ca 100644
--- a/tests/PureAnnotationTest.php
+++ b/tests/PureAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/PureCallableTest.php b/tests/PureCallableTest.php
index 79817fb3a..6360ee554 100644
--- a/tests/PureCallableTest.php
+++ b/tests/PureCallableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ReadonlyPropertyTest.php b/tests/ReadonlyPropertyTest.php
index 3c9d2b394..d99905139 100644
--- a/tests/ReadonlyPropertyTest.php
+++ b/tests/ReadonlyPropertyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ReferenceConstraintTest.php b/tests/ReferenceConstraintTest.php
index 1c6dd4c6a..9fcd325ac 100644
--- a/tests/ReferenceConstraintTest.php
+++ b/tests/ReferenceConstraintTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ReferenceTest.php b/tests/ReferenceTest.php
index 81e639572..20819d3ac 100644
--- a/tests/ReferenceTest.php
+++ b/tests/ReferenceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/ReportOutputTest.php b/tests/ReportOutputTest.php
index c26483d90..bee44b19d 100644
--- a/tests/ReportOutputTest.php
+++ b/tests/ReportOutputTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use DOMDocument;
diff --git a/tests/ReturnTypeProvider/ArrayColumnTest.php b/tests/ReturnTypeProvider/ArrayColumnTest.php
index ea6a8d604..143557369 100644
--- a/tests/ReturnTypeProvider/ArrayColumnTest.php
+++ b/tests/ReturnTypeProvider/ArrayColumnTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/ArraySliceTest.php b/tests/ReturnTypeProvider/ArraySliceTest.php
index 83bbba768..f2d839b9f 100644
--- a/tests/ReturnTypeProvider/ArraySliceTest.php
+++ b/tests/ReturnTypeProvider/ArraySliceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/BasenameTest.php b/tests/ReturnTypeProvider/BasenameTest.php
index 5c624651f..701255887 100644
--- a/tests/ReturnTypeProvider/BasenameTest.php
+++ b/tests/ReturnTypeProvider/BasenameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/DirnameTest.php b/tests/ReturnTypeProvider/DirnameTest.php
index 48dea4d2c..894bd1c1c 100644
--- a/tests/ReturnTypeProvider/DirnameTest.php
+++ b/tests/ReturnTypeProvider/DirnameTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/ExceptionCodeTest.php b/tests/ReturnTypeProvider/ExceptionCodeTest.php
index cf7863415..b78cc4aa5 100644
--- a/tests/ReturnTypeProvider/ExceptionCodeTest.php
+++ b/tests/ReturnTypeProvider/ExceptionCodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/InArrayTest.php b/tests/ReturnTypeProvider/InArrayTest.php
index 2020187ce..e56855d3e 100644
--- a/tests/ReturnTypeProvider/InArrayTest.php
+++ b/tests/ReturnTypeProvider/InArrayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php b/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php
index da67246e2..fed70c3e7 100644
--- a/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php
+++ b/tests/ReturnTypeProvider/MinMaxReturnTypeProviderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php b/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php
index f42851856..76c845002 100644
--- a/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php
+++ b/tests/ReturnTypeProvider/PowReturnTypeProviderTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeProvider/SprintfTest.php b/tests/ReturnTypeProvider/SprintfTest.php
index cc2a54f04..b5674c490 100644
--- a/tests/ReturnTypeProvider/SprintfTest.php
+++ b/tests/ReturnTypeProvider/SprintfTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\ReturnTypeProvider;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/ReturnTypeTest.php b/tests/ReturnTypeTest.php
index 275f093c0..2caf02089 100644
--- a/tests/ReturnTypeTest.php
+++ b/tests/ReturnTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/StubTest.php b/tests/StubTest.php
index 55d61ffbe..4ea6f2198 100644
--- a/tests/StubTest.php
+++ b/tests/StubTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/SuperGlobalsTest.php b/tests/SuperGlobalsTest.php
index e0e33418e..42e6212d6 100644
--- a/tests/SuperGlobalsTest.php
+++ b/tests/SuperGlobalsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/SwitchTypeTest.php b/tests/SwitchTypeTest.php
index c8bd80ed9..1b685bb59 100644
--- a/tests/SwitchTypeTest.php
+++ b/tests/SwitchTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/TaintTest.php b/tests/TaintTest.php
index 4a847bd4b..d685014c2 100644
--- a/tests/TaintTest.php
+++ b/tests/TaintTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/Template/ClassStringMapTest.php b/tests/Template/ClassStringMapTest.php
index c5105462d..78ed8b7f3 100644
--- a/tests/Template/ClassStringMapTest.php
+++ b/tests/Template/ClassStringMapTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/ClassTemplateCovarianceTest.php b/tests/Template/ClassTemplateCovarianceTest.php
index aac358149..f82c3bc41 100644
--- a/tests/Template/ClassTemplateCovarianceTest.php
+++ b/tests/Template/ClassTemplateCovarianceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/ClassTemplateExtendsTest.php b/tests/Template/ClassTemplateExtendsTest.php
index 130c178d5..d7e237f5c 100644
--- a/tests/Template/ClassTemplateExtendsTest.php
+++ b/tests/Template/ClassTemplateExtendsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/ClassTemplateTest.php b/tests/Template/ClassTemplateTest.php
index 3858da04d..0c6c4ab4a 100644
--- a/tests/Template/ClassTemplateTest.php
+++ b/tests/Template/ClassTemplateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/ConditionalReturnTypeTest.php b/tests/Template/ConditionalReturnTypeTest.php
index 18669470a..5bf824e9b 100644
--- a/tests/Template/ConditionalReturnTypeTest.php
+++ b/tests/Template/ConditionalReturnTypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/FunctionClassStringTemplateTest.php b/tests/Template/FunctionClassStringTemplateTest.php
index d4166943f..6f84801a6 100644
--- a/tests/Template/FunctionClassStringTemplateTest.php
+++ b/tests/Template/FunctionClassStringTemplateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/FunctionTemplateAssertTest.php b/tests/Template/FunctionTemplateAssertTest.php
index 94eed8658..5ecc63379 100644
--- a/tests/Template/FunctionTemplateAssertTest.php
+++ b/tests/Template/FunctionTemplateAssertTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/FunctionTemplateTest.php b/tests/Template/FunctionTemplateTest.php
index ba72c2604..d746d4458 100644
--- a/tests/Template/FunctionTemplateTest.php
+++ b/tests/Template/FunctionTemplateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/NestedTemplateTest.php b/tests/Template/NestedTemplateTest.php
index dbbcdc7e3..fd33578bc 100644
--- a/tests/Template/NestedTemplateTest.php
+++ b/tests/Template/NestedTemplateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/PropertiesOfTemplateTest.php b/tests/Template/PropertiesOfTemplateTest.php
index a57247511..aba8efd9d 100644
--- a/tests/Template/PropertiesOfTemplateTest.php
+++ b/tests/Template/PropertiesOfTemplateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/Template/TraitTemplateTest.php b/tests/Template/TraitTemplateTest.php
index 8fd8d9317..86cf5d8f0 100644
--- a/tests/Template/TraitTemplateTest.php
+++ b/tests/Template/TraitTemplateTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Template;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TestCase.php b/tests/TestCase.php
index 92c7300b1..8e61664f8 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PHPUnit\Framework\TestCase as BaseTestCase;
diff --git a/tests/TestConfig.php b/tests/TestConfig.php
index abb932844..a41360eab 100644
--- a/tests/TestConfig.php
+++ b/tests/TestConfig.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/TestEnvironmentTest.php b/tests/TestEnvironmentTest.php
index 5a1237912..7b6a1b587 100644
--- a/tests/TestEnvironmentTest.php
+++ b/tests/TestEnvironmentTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use PHPUnit\Framework\TestCase as PHPUnitTestCase;
diff --git a/tests/ThisOutTest.php b/tests/ThisOutTest.php
index a537996ae..adc1ad20b 100644
--- a/tests/ThisOutTest.php
+++ b/tests/ThisOutTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\ValidCodeAnalysisTestTrait;
diff --git a/tests/ThrowsAnnotationTest.php b/tests/ThrowsAnnotationTest.php
index 4673e056b..893005412 100644
--- a/tests/ThrowsAnnotationTest.php
+++ b/tests/ThrowsAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/ThrowsInGlobalScopeTest.php b/tests/ThrowsInGlobalScopeTest.php
index afdc9029d..b22f8e7a8 100644
--- a/tests/ThrowsInGlobalScopeTest.php
+++ b/tests/ThrowsInGlobalScopeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/ToStringTest.php b/tests/ToStringTest.php
index d010a365c..f0c3a4892 100644
--- a/tests/ToStringTest.php
+++ b/tests/ToStringTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/TraceTest.php b/tests/TraceTest.php
index 26aea7553..564fd7475 100644
--- a/tests/TraceTest.php
+++ b/tests/TraceTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/TraitTest.php b/tests/TraitTest.php
index 4b04b7c4e..4daae48a3 100644
--- a/tests/TraitTest.php
+++ b/tests/TraitTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/Traits/InvalidCodeAnalysisTestTrait.php b/tests/Traits/InvalidCodeAnalysisTestTrait.php
index 10bb8ea3e..e5a06f4e8 100644
--- a/tests/Traits/InvalidCodeAnalysisTestTrait.php
+++ b/tests/Traits/InvalidCodeAnalysisTestTrait.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Traits;
 
 use Psalm\Config;
@@ -49,7 +51,7 @@ trait InvalidCodeAnalysisTestTrait
         string $code,
         string $error_message,
         array  $error_levels = [],
-        string $php_version = '7.4'
+        string $php_version = '7.4',
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'PHP80-') !== false) {
diff --git a/tests/Traits/ValidCodeAnalysisTestTrait.php b/tests/Traits/ValidCodeAnalysisTestTrait.php
index b37acced3..e8b7ffce8 100644
--- a/tests/Traits/ValidCodeAnalysisTestTrait.php
+++ b/tests/Traits/ValidCodeAnalysisTestTrait.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\Traits;
 
 use Psalm\Config;
@@ -41,7 +43,7 @@ trait ValidCodeAnalysisTestTrait
         string $code,
         array $assertions = [],
         array $ignored_issues = [],
-        string $php_version = '7.4'
+        string $php_version = '7.4',
     ): void {
         $test_name = $this->getTestName();
         if (strpos($test_name, 'PHP80-') !== false) {
diff --git a/tests/TryCatchTest.php b/tests/TryCatchTest.php
index c83e2b091..87a714e23 100644
--- a/tests/TryCatchTest.php
+++ b/tests/TryCatchTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeAnnotationTest.php b/tests/TypeAnnotationTest.php
index 8cd1fb218..42cdbf5c7 100644
--- a/tests/TypeAnnotationTest.php
+++ b/tests/TypeAnnotationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/TypeCombinationTest.php b/tests/TypeCombinationTest.php
index c3371ef2a..f53f15300 100644
--- a/tests/TypeCombinationTest.php
+++ b/tests/TypeCombinationTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Internal\Type\TypeCombiner;
diff --git a/tests/TypeComparatorTest.php b/tests/TypeComparatorTest.php
index 6a2d093f5..434a1f304 100644
--- a/tests/TypeComparatorTest.php
+++ b/tests/TypeComparatorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Internal\Analyzer\ProjectAnalyzer;
diff --git a/tests/TypeParseTest.php b/tests/TypeParseTest.php
index 3aecbf7b0..2ebae82ce 100644
--- a/tests/TypeParseTest.php
+++ b/tests/TypeParseTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Codebase;
diff --git a/tests/TypeReconciliation/ArrayKeyExistsTest.php b/tests/TypeReconciliation/ArrayKeyExistsTest.php
index 3ee780251..4c96c6783 100644
--- a/tests/TypeReconciliation/ArrayKeyExistsTest.php
+++ b/tests/TypeReconciliation/ArrayKeyExistsTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Config;
diff --git a/tests/TypeReconciliation/AssignmentInConditionalTest.php b/tests/TypeReconciliation/AssignmentInConditionalTest.php
index 70a476ae8..ab6f517ac 100644
--- a/tests/TypeReconciliation/AssignmentInConditionalTest.php
+++ b/tests/TypeReconciliation/AssignmentInConditionalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/ConditionalTest.php b/tests/TypeReconciliation/ConditionalTest.php
index 21fcc1638..da1d639e2 100644
--- a/tests/TypeReconciliation/ConditionalTest.php
+++ b/tests/TypeReconciliation/ConditionalTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/EmptyTest.php b/tests/TypeReconciliation/EmptyTest.php
index c79918044..5476be279 100644
--- a/tests/TypeReconciliation/EmptyTest.php
+++ b/tests/TypeReconciliation/EmptyTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/InArrayTest.php b/tests/TypeReconciliation/InArrayTest.php
index 77e182cc0..ff584d63a 100644
--- a/tests/TypeReconciliation/InArrayTest.php
+++ b/tests/TypeReconciliation/InArrayTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/IssetTest.php b/tests/TypeReconciliation/IssetTest.php
index c15612692..e4485c790 100644
--- a/tests/TypeReconciliation/IssetTest.php
+++ b/tests/TypeReconciliation/IssetTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/ReconcilerTest.php b/tests/TypeReconciliation/ReconcilerTest.php
index 0f6e9e880..5c1b0a150 100644
--- a/tests/TypeReconciliation/ReconcilerTest.php
+++ b/tests/TypeReconciliation/ReconcilerTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Context;
diff --git a/tests/TypeReconciliation/RedundantConditionTest.php b/tests/TypeReconciliation/RedundantConditionTest.php
index 88142c718..b6e01460c 100644
--- a/tests/TypeReconciliation/RedundantConditionTest.php
+++ b/tests/TypeReconciliation/RedundantConditionTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/ScopeTest.php b/tests/TypeReconciliation/ScopeTest.php
index 19d2c0b95..b94ac5a90 100644
--- a/tests/TypeReconciliation/ScopeTest.php
+++ b/tests/TypeReconciliation/ScopeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/TypeAlgebraTest.php b/tests/TypeReconciliation/TypeAlgebraTest.php
index aea50a778..522096eb3 100644
--- a/tests/TypeReconciliation/TypeAlgebraTest.php
+++ b/tests/TypeReconciliation/TypeAlgebraTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/TypeTest.php b/tests/TypeReconciliation/TypeTest.php
index b0f4e78df..475e4a0fa 100644
--- a/tests/TypeReconciliation/TypeTest.php
+++ b/tests/TypeReconciliation/TypeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Tests\TestCase;
diff --git a/tests/TypeReconciliation/ValueTest.php b/tests/TypeReconciliation/ValueTest.php
index 10df00217..3c5b0c676 100644
--- a/tests/TypeReconciliation/ValueTest.php
+++ b/tests/TypeReconciliation/ValueTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests\TypeReconciliation;
 
 use Psalm\Internal\Analyzer\ProjectAnalyzer;
diff --git a/tests/UnresolvableIncludeTest.php b/tests/UnresolvableIncludeTest.php
index a245c443b..dec1ae9b7 100644
--- a/tests/UnresolvableIncludeTest.php
+++ b/tests/UnresolvableIncludeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Context;
diff --git a/tests/UnusedCodeTest.php b/tests/UnusedCodeTest.php
index 4915ffdb6..87e187265 100644
--- a/tests/UnusedCodeTest.php
+++ b/tests/UnusedCodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/UnusedVariableTest.php b/tests/UnusedVariableTest.php
index 57f1a425d..fb7583943 100644
--- a/tests/UnusedVariableTest.php
+++ b/tests/UnusedVariableTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Tests\Traits\InvalidCodeAnalysisTestTrait;
diff --git a/tests/VariadicTest.php b/tests/VariadicTest.php
index a7aba476e..f8d67d762 100644
--- a/tests/VariadicTest.php
+++ b/tests/VariadicTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Psalm\Tests;
 
 use Psalm\Config;
diff --git a/tests/somefile.php b/tests/somefile.php
index 1ce2c088a..783c5db66 100644
--- a/tests/somefile.php
+++ b/tests/somefile.php
@@ -1,2 +1,5 @@
 <?php
+
+declare(strict_types=1);
+
 //placeholder file to have a real file when analysing tests