diff --git a/tests/FileDiffTest.php b/tests/FileDiffTest.php
index 4f767e383..7f6465fbe 100644
--- a/tests/FileDiffTest.php
+++ b/tests/FileDiffTest.php
@@ -164,7 +164,6 @@ class FileDiffTest extends TestCase
                 $b_doc = $b_stmt->getDocComment();
 
                 $this->assertNotNull($b_doc, var_export($a_doc, true));
-                assert(!is_null($b_doc));
 
                 $this->assertNotSame($a_doc, $b_doc);
 
@@ -188,7 +187,10 @@ class FileDiffTest extends TestCase
             if (isset($a_stmt->stmts)) {
                 $this->assertTrue(isset($b_stmt->stmts));
 
-                /** @psalm-suppress UndefinedPropertyFetch */
+                /**
+                 * @psalm-suppress UndefinedPropertyFetch
+                 * @psalm-suppress MixedArgument
+                 */
                 $this->assertTreesEqual($a_stmt->stmts, $b_stmt->stmts);
             }
         }
diff --git a/tests/LanguageServer/SymbolLookupTest.php b/tests/LanguageServer/SymbolLookupTest.php
index 6ce00b2ad..aefa43e5a 100644
--- a/tests/LanguageServer/SymbolLookupTest.php
+++ b/tests/LanguageServer/SymbolLookupTest.php
@@ -120,7 +120,6 @@ class SymbolLookupTest extends \Psalm\Tests\TestCase
         $method_symbol_location = $codebase->getSymbolLocation('somefile.php', 'B\A::foo()');
 
         $this->assertNotNull($method_symbol_location);
-        assert(!is_null($method_symbol_location));
         $this->assertSame(10, $method_symbol_location->getLineNumber());
         $this->assertSame(21, $method_symbol_location->getColumn());
 
@@ -128,7 +127,6 @@ class SymbolLookupTest extends \Psalm\Tests\TestCase
         $property_symbol_location = $codebase->getSymbolLocation('somefile.php', 'B\A::$a');
 
         $this->assertNotNull($property_symbol_location);
-        assert(!is_null($property_symbol_location));
         $this->assertSame(6, $property_symbol_location->getLineNumber());
         $this->assertSame(31, $property_symbol_location->getColumn());
 
@@ -136,7 +134,6 @@ class SymbolLookupTest extends \Psalm\Tests\TestCase
         $constant_symbol_location = $codebase->getSymbolLocation('somefile.php', 'B\A::BANANA');
 
         $this->assertNotNull($constant_symbol_location);
-        assert(!is_null($constant_symbol_location));
         $this->assertSame(8, $constant_symbol_location->getLineNumber());
         $this->assertSame(27, $constant_symbol_location->getColumn());
 
@@ -144,7 +141,6 @@ class SymbolLookupTest extends \Psalm\Tests\TestCase
         $function_symbol_location = $codebase->getSymbolLocation('somefile.php', 'B\bar()');
 
         $this->assertNotNull($function_symbol_location);
-        assert(!is_null($function_symbol_location));
         $this->assertSame(13, $function_symbol_location->getLineNumber());
         $this->assertSame(17, $function_symbol_location->getColumn());
     }
@@ -217,7 +213,6 @@ class SymbolLookupTest extends \Psalm\Tests\TestCase
         $symbol_at_position = $codebase->getReferenceAtPosition('somefile.php', new Position(10, 30));
 
         $this->assertNotNull($symbol_at_position);
-        assert(!is_null($symbol_at_position));
 
         $this->assertSame('type: int|null', $symbol_at_position[0]);
 
diff --git a/tests/PluginListTest.php b/tests/PluginListTest.php
index 9dd5a9b48..79b9c58ef 100644
--- a/tests/PluginListTest.php
+++ b/tests/PluginListTest.php
@@ -10,11 +10,13 @@ use Psalm\Internal\PluginManager\PluginList;
 /** @group PluginManager */
 class PluginListTest extends TestCase
 {
-    /** @var ObjectProphecy */
+    /** @var ObjectProphecy<ConfigFile> */
     private $config_file;
-    /** @var ObjectProphecy */
+
+    /** @var ObjectProphecy<Config> */
     private $config;
-    /** @var ObjectProphecy */
+
+    /** @var ObjectProphecy<ComposerLock> */
     private $composer_lock;
 
     public function setUp()
diff --git a/tests/ProjectCheckerTest.php b/tests/ProjectCheckerTest.php
index 22bb91d24..6aed6511f 100644
--- a/tests/ProjectCheckerTest.php
+++ b/tests/ProjectCheckerTest.php
@@ -151,7 +151,10 @@ class ProjectAnalyzerTest extends TestCase
             )
         );
 
-        $this->project_analyzer->getCodebase()->config->after_codebase_populated[] = get_class($hook);
+        $hook_class = get_class($hook);
+
+        /** @psalm-suppress TypeCoercion see vimeo/psalm#1397 */
+        $this->project_analyzer->getCodebase()->config->after_codebase_populated[] = $hook_class;
 
         ob_start();
         $this->project_analyzer->check('tests/DummyProject');