diff --git a/composer.json b/composer.json
index eb970cc..d84e31b 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,8 @@
         "async-interop/event-loop-implementation": "dev-master"
     },
     "require-dev": {
-        "amphp/loop": "dev-master"
+        "amphp/loop": "dev-master",
+        "phpunit/phpunit": "^4|^5"
     },
     "minimum-stability": "dev",
     "autoload": {
diff --git a/lib/Deferred.php b/lib/Deferred.php
index 5b9f61b..1ce59ba 100644
--- a/lib/Deferred.php
+++ b/lib/Deferred.php
@@ -4,6 +4,7 @@ namespace Amp;
 
 use Interop\Async\Awaitable;
 
+// @codeCoverageIgnoreStart
 try {
     if (@assert(false)) {
         production: // PHP 7 production environment (zend.assertions=0)
@@ -75,4 +76,4 @@ try {
     }
 } catch (\AssertionError $exception) {
     goto development; // zend.assertions=1 and assert.exception=1, use development definition.
-}
+} // @codeCoverageIgnoreEnd
diff --git a/lib/functions.php b/lib/functions.php
index d16983d..c0d67b2 100644
--- a/lib/functions.php
+++ b/lib/functions.php
@@ -144,13 +144,23 @@ function capture(Awaitable $awaitable, $className, callable $functor) {
  */
 function timeout(Awaitable $awaitable, $timeout) {
     $deferred = new Deferred;
+    $resolved = false;
 
-    $watcher = Loop::delay($timeout, function () use ($deferred) {
-        $deferred->fail(new TimeoutException);
+    $watcher = Loop::delay($timeout, function () use (&$resolved, $deferred) {
+        if (!$resolved) {
+            $resolved = true;
+            $deferred->fail(new TimeoutException);
+        }
     });
 
-    $awaitable->when(function () use ($awaitable, $deferred, $watcher) {
+    $awaitable->when(function () use (&$resolved, $awaitable, $deferred, $watcher) {
         Loop::cancel($watcher);
+
+        if ($resolved) {
+            return;
+        }
+
+        $resolved = true;
         $deferred->resolve($awaitable);
     });
 
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
new file mode 100644
index 0000000..dfc05dd
--- /dev/null
+++ b/phpunit.xml.dist
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/4.1/phpunit.xsd"
+    backupGlobals="false"
+    backupStaticAttributes="false"
+    bootstrap="vendor/autoload.php"
+    colors="true"
+    convertErrorsToExceptions="true"
+    convertNoticesToExceptions="true"
+    convertWarningsToExceptions="true"
+    processIsolation="false"
+    stopOnFailure="false"
+>
+    <testsuites>
+        <testsuite name="Amp">
+            <directory>test</directory>
+            <!-- Remove tags below once PHP 7.0 is required -->
+            <exclude>test/ExtendedCoroutineTest.php</exclude>
+            <file phpVersion="7.0.0">test/ExtendedCoroutineTest.php</file>
+        </testsuite>
+    </testsuites>
+    <filter>
+        <whitelist>
+            <directory suffix=".php">lib</directory>
+        </whitelist>
+    </filter>
+    <logging>
+        <log type="coverage-html" target="build/coverage" title="Icicle" highlight="true"/>
+    </logging>
+</phpunit>
\ No newline at end of file
diff --git a/test/AdaptTest.php b/test/AdaptTest.php
new file mode 100644
index 0000000..9a7255d
--- /dev/null
+++ b/test/AdaptTest.php
@@ -0,0 +1,105 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Amp\Success;
+use Interop\Async\Awaitable;
+
+class PromiseMock {
+    /**
+     * @var \Interop\Async\Awaitable
+     */
+    private $awaitable;
+
+    public function __construct(Awaitable $awaitable) {
+        $this->awaitable = $awaitable;
+    }
+
+    public function then(callable $onFulfilled = null, callable $onRejected = null) {
+        $this->awaitable->when(function ($exception, $value) use ($onFulfilled, $onRejected) {
+            if ($exception) {
+                if ($onRejected) {
+                    $onRejected($exception);
+                }
+                return;
+            }
+
+            if ($onFulfilled) {
+                $onFulfilled($value);
+            }
+        });
+    }
+}
+
+class AdaptTest extends \PHPUnit_Framework_TestCase {
+    public function testThenCalled() {
+        $mock = $this->getMockBuilder(PromiseMock::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        
+        $mock->expects($this->once())
+            ->method("then")
+            ->with(
+                $this->callback(function ($resolve) {
+                    return is_callable($resolve);
+                }),
+                $this->callback(function ($reject) {
+                    return is_callable($reject);
+                })
+            );
+        
+        $awaitable = Amp\adapt($mock);
+        
+        $this->assertInstanceOf(Awaitable::class, $awaitable);
+    }
+    
+    /**
+     * @depends testThenCalled
+     */
+    public function testAwaitableFulfilled() {
+        $value = 1;
+
+        $promise = new PromiseMock(new Success($value));
+
+        $awaitable = Amp\adapt($promise);
+
+        $awaitable->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+        $this->assertSame($value, $result);
+    }
+    
+    /**
+     * @depends testThenCalled
+     */
+    public function testAwaitableRejected() {
+        $exception = new \Exception;
+
+        $promise = new PromiseMock(new Failure($exception));
+
+        $awaitable = Amp\adapt($promise);
+
+        $awaitable->when(function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertSame($exception, $reason);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function testScalarValue() {
+        Amp\adapt(1);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function testNonThenableObject() {
+        Amp\adapt(new \stdClass);
+    }
+}
diff --git a/test/AllTest.php b/test/AllTest.php
new file mode 100644
index 0000000..8d13a06
--- /dev/null
+++ b/test/AllTest.php
@@ -0,0 +1,77 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Pause;
+use Amp\Success;
+use Interop\Async\Loop;
+
+class AllTest extends \PHPUnit_Framework_TestCase {
+    public function testEmptyArray() {
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        Amp\all([])->when($callback);
+
+        $this->assertSame([], $result);
+    }
+
+    public function testSuccessfulAwaitablesArray() {
+        $awaitables = [new Success(1), new Success(2), new Success(3)];
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        Amp\all($awaitables)->when($callback);
+
+        $this->assertSame([1, 2, 3], $result);
+    }
+
+    public function testPendingAwatiablesArray() {
+        Loop::execute(function () use (&$result) {
+            $awaitables = [
+                new Pause(0.2, 1),
+                new Pause(0.3, 2),
+                new Pause(0.1, 3),
+            ];
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            Amp\all($awaitables)->when($callback);
+        });
+
+        $this->assertEquals([1, 2, 3], $result);
+    }
+
+    public function testArrayKeysPreserved() {
+        $expected = ['one' => 1, 'two' => 2, 'three' => 3];
+
+        Loop::execute(function () use (&$result) {
+            $awaitables = [
+                'one'   => new Pause(0.2, 1),
+                'two'   => new Pause(0.3, 2),
+                'three' => new Pause(0.1, 3),
+            ];
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            Amp\all($awaitables)->when($callback);
+        });
+
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function testNonAwaitable() {
+        Amp\all([1]);
+    }
+}
diff --git a/test/CaptureTest.php b/test/CaptureTest.php
new file mode 100644
index 0000000..28b11d8
--- /dev/null
+++ b/test/CaptureTest.php
@@ -0,0 +1,113 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Amp\Success;
+use Interop\Async\Awaitable;
+
+class CaptureTest extends \PHPUnit_Framework_TestCase {
+    public function testSuccessfulAwaitable() {
+        $invoked = false;
+        $callback = function ($exception) use (&$invoked) {
+            $invoked = true;
+            return -1;
+        };
+
+        $value = 1;
+
+        $awaitable = new Success($value);
+
+        $awaitable = Amp\capture($awaitable, \Exception::class, $callback);
+        $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        $awaitable->when($callback);
+
+        $this->assertFalse($invoked);
+        $this->assertSame($value, $result);
+    }
+
+    public function testFailedAwaitable() {
+        $invoked = false;
+        $callback = function ($exception) use (&$invoked, &$reason) {
+            $invoked = true;
+            $reason = $exception;
+            return -1;
+        };
+
+        $exception = new \Exception;
+
+        $awaitable = new Failure($exception);
+
+        $awaitable = Amp\capture($awaitable, \Exception::class, $callback);
+        $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        $awaitable->when($callback);
+
+        $this->assertTrue($invoked);
+        $this->assertSame($exception, $reason);
+        $this->assertSame(-1, $result);
+    }
+    
+    /**
+     * @depends testFailedAwaitable
+     */
+    public function testCallbackThrowing() {
+        $invoked = false;
+        $callback = function ($exception) use (&$invoked) {
+            $invoked = true;
+            throw new \Exception;
+        };
+
+        $exception = new \Exception;
+
+        $awaitable = new Failure($exception);
+
+        $awaitable = Amp\capture($awaitable, \Exception::class, $callback);
+
+        $callback = function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        };
+
+        $awaitable->when($callback);
+
+        $this->assertTrue($invoked);
+        $this->assertNotSame($exception, $reason);
+    }
+
+    /**
+     * @depends testFailedAwaitable
+     */
+    public function testUnmatchedExceptionClass() {
+        $invoked = false;
+        $callback = function ($exception) use (&$invoked, &$reason) {
+            $invoked = true;
+            $reason = $exception;
+            return -1;
+        };
+
+        $exception = new \LogicException;
+
+        $awaitable = new Failure($exception);
+
+        $awaitable = Amp\capture($awaitable, \RuntimeException::class, $callback);
+
+        $callback = function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        };
+
+        $awaitable->when($callback);
+
+        $this->assertFalse($invoked);
+        $this->assertSame($exception, $reason);
+    }
+}
diff --git a/test/CoroutineTest.php b/test/CoroutineTest.php
new file mode 100644
index 0000000..350c798
--- /dev/null
+++ b/test/CoroutineTest.php
@@ -0,0 +1,539 @@
+<?php
+
+namespace Icicle\Tests\Coroutine;
+
+use Amp;
+use Amp\Coroutine;
+use Amp\Failure;
+use Amp\InvalidYieldException;
+use Amp\Pause;
+use Amp\Success;
+use Interop\Async\Loop;
+
+class CoroutineTest extends \PHPUnit_Framework_TestCase {
+    const TIMEOUT = 0.1;
+
+    public function testYieldSuccessfulAwaitable() {
+        $value = 1;
+
+        $generator = function () use (&$yielded, $value) {
+            $yielded = (yield new Success($value));
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $this->assertSame($value, $yielded);
+    }
+
+    public function testYieldFailedAwaitable() {
+        $exception = new \Exception;
+
+        $generator = function () use (&$yielded, $exception) {
+            $yielded = (yield new Failure($exception));
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $this->assertNull($yielded);
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertSame($exception, $reason);
+    }
+
+    /**
+     * @depends testYieldSuccessfulAwaitable
+     */
+    public function testYieldPendingAwaitable() {
+        $value = 1;
+
+        Loop::execute(function () use (&$yielded, $value) {
+            $generator = function () use (&$yielded, $value) {
+                $yielded = (yield new Pause(self::TIMEOUT, $value));
+            };
+
+            $coroutine = new Coroutine($generator());
+        });
+
+        $this->assertSame($value, $yielded);
+    }
+
+    /**
+     * @depends testYieldFailedAwaitable
+     */
+    public function testCatchingFailedAwaitableException() {
+        $exception = new \Exception;
+
+        $fail = false;
+        $generator = function () use (&$fail, &$result, $exception) {
+            try {
+                yield new Failure($exception);
+            } catch (\Exception $exception) {
+                $result = $exception;
+                return;
+            }
+
+            $fail = true;
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        if ($fail) {
+            $this->fail("Failed awaitable reason not thrown into generator");
+        }
+
+    }
+
+    /**
+     * @todo Remove once PHP 7 is required.
+     */
+    public function testSucceedsWithCoroutineResult() {
+        $value = 1;
+
+        $generator = function () use ($value) {
+            yield Coroutine::result($value);
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testSucceedsWithCoroutineResult
+     * @todo Remove once PHP 7 is required.
+     */
+    public function testSucceedsWithCoroutineAfterSuccessfulAwaitable() {
+        $value = 1;
+
+        $generator = function () use ($value) {
+            yield Coroutine::result(yield new Success($value));
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testSucceedsWithCoroutineResult
+     * @todo Remove once PHP 7 is required.
+     */
+    public function testSucceedsWithCoroutineAfterFailedAwaitable() {
+        $value = 1;
+
+        $generator = function () use ($value) {
+            try {
+                yield new Failure(new \Exception);
+            } catch (\Exception $exception) {
+                yield Coroutine::result($value);
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+        $this->assertSame($value, $result);
+    }
+
+    public function testInvalidYield() {
+        $generator = function () {
+            yield 1;
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertInstanceOf(InvalidYieldException::class, $reason);
+    }
+
+    /**
+     * @depends testInvalidYield
+     */
+    public function testInvalidYieldAfterYieldAwaitable() {
+        $generator = function () {
+            yield new Success;
+            yield 1;
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertInstanceOf(InvalidYieldException::class, $reason);
+    }
+
+    /**
+     * @depends testInvalidYield
+     */
+    public function testCatchesExceptionAfterInvalidYield() {
+        $generator = function () {
+            try {
+                yield 1;
+            } catch (\Exception $exception) {
+                yield Coroutine::result(1);
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertInstanceOf(InvalidYieldException::class, $reason);
+    }
+
+    /**
+     * @depends testSucceedsWithCoroutineResult
+     * @todo Remove once PHP 7 is required.
+     */
+    public function testYieldsAfterCoroutineResult() {
+        $generator = function () {
+            yield Coroutine::result(1);
+            yield new Success;
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertInstanceOf(InvalidYieldException::class, $reason);
+    }
+
+    /**
+     * @depends testYieldsAfterCoroutineResult
+     * @todo Remove once PHP 7 is required.
+     */
+    public function testCatchesExceptionAfterInvalidResult() {
+        $generator = function () {
+            yield Coroutine::result(1);
+
+            try {
+                yield new Success;
+            } catch (\Exception $exception) {
+                yield Coroutine::result(2);
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertInstanceOf(InvalidYieldException::class, $reason);
+    }
+
+    /**
+     * @depends testInvalidYield
+     */
+    public function testThrowAfterInvalidYield() {
+        $exception = new \Exception;
+
+        $generator = function () use ($exception) {
+            try {
+                yield 1;
+            } catch (\Exception $reason) {
+                throw $exception;
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertInstanceOf(InvalidYieldException::class, $reason);
+        $this->assertSame($exception, $reason->getPrevious());
+    }
+
+    /**
+     * @depends testYieldFailedAwaitable
+     */
+    public function testCatchingFailedAwaitableExceptionWithNoFurtherYields() {
+        $exception = new \Exception;
+
+        $generator = function () use ($exception) {
+            try {
+                yield new Failure($exception);
+            } catch (\Exception $exception) {
+                // No further yields in generator.
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+        $this->assertNull($result);
+    }
+
+    public function testGeneratorThrowingExceptionFailsCoroutine() {
+        $exception = new \Exception;
+
+        $generator = function () use ($exception) {
+            throw $exception;
+            yield;
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertSame($exception, $reason);
+    }
+
+    /**
+     * @depends testGeneratorThrowingExceptionFailsCoroutine
+     */
+    public function testGeneratorThrowingExceptionWithFinallyFailsCoroutine() {
+        $exception = new \Exception;
+
+        $invoked = false;
+        $generator = function () use (&$invoked, $exception) {
+            try {
+                throw $exception;
+                yield;
+            } finally {
+                $invoked = true;
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertSame($exception, $reason);
+        $this->assertTrue($invoked);
+    }
+
+    /**
+     * @depends testYieldFailedAwaitable
+     * @depends testGeneratorThrowingExceptionWithFinallyFailsCoroutine
+     */
+    public function testGeneratorYieldingFailedAwaitableWithFinallyFailsCoroutine() {
+        $exception = new \Exception;
+
+        $invoked = false;
+        $generator = function () use (&$invoked, $exception) {
+            try {
+                yield new Failure($exception);
+            } finally {
+                $invoked = true;
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertSame($exception, $reason);
+        $this->assertTrue($invoked);
+    }
+
+    /**
+     * @depends testGeneratorThrowingExceptionFailsCoroutine
+     */
+    public function testGeneratorThrowingExceptionAfterPendingAwaitableWithFinallyFailsCoroutine() {
+        $exception = new \Exception;
+        $value = 1;
+
+        Loop::execute(function () use (&$yielded, &$invoked, &$reason, $exception, $value) {
+            $invoked = false;
+            $generator = function () use (&$yielded, &$invoked, $exception, $value) {
+                try {
+                    $yielded = (yield new Pause(self::TIMEOUT, $value));
+                    throw $exception;
+                } finally {
+                    $invoked = true;
+                }
+            };
+
+            $coroutine = new Coroutine($generator());
+
+            $coroutine->when(function ($exception, $value) use (&$reason) {
+                $reason = $exception;
+            });
+        });
+
+        $this->assertSame($exception, $reason);
+        $this->assertTrue($invoked);
+        $this->assertSame($value, $yielded);
+    }
+
+    /**
+     * Note that yielding in a finally block is not recommended.
+     *
+     * @depends testYieldPendingAwaitable
+     * @depends testGeneratorThrowingExceptionWithFinallyFailsCoroutine
+     */
+    public function testGeneratorThrowingExceptionWithFinallyYieldingPendingAwaitable() {
+        $exception = new \Exception;
+        $value = 1;
+
+        Loop::execute(function () use (&$yielded, &$reason, $exception, $value) {
+            $generator = function () use (&$yielded, $exception, $value) {
+                try {
+                    throw $exception;
+                } finally {
+                    $yielded = (yield new Pause(self::TIMEOUT, $value));
+                }
+            };
+
+            $coroutine = new Coroutine($generator());
+
+            $coroutine->when(function ($exception, $value) use (&$reason) {
+                $reason = $exception;
+            });
+        });
+
+        $this->assertSame($value, $yielded);
+        $this->assertSame($exception, $reason);
+    }
+
+    /**
+     * @depends testYieldPendingAwaitable
+     * @depends testGeneratorThrowingExceptionWithFinallyFailsCoroutine
+     */
+    public function testGeneratorThrowingExceptionWithFinallyBlockThrowing() {
+        $exception = new \Exception;
+
+        $generator = function () use ($exception) {
+            try {
+                throw new \Exception;
+            } finally {
+                throw $exception;
+            }
+
+            yield; // Unreachable, but makes function a generator.
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        });
+
+        $this->assertSame($exception, $reason);
+    }
+
+    /**
+     * @depends testYieldSuccessfulAwaitable
+     */
+    public function testYieldConsecutiveSucceeded() {
+        $invoked = false;
+        Loop::execute(function () use (&$invoked) {
+            $count = 1000;
+            $awaitable = new Success;
+
+            $generator = function () use ($count, $awaitable) {
+                for ($i = 0; $i < $count; ++$i) {
+                    yield $awaitable;
+                }
+            };
+
+            $coroutine = new Coroutine($generator());
+
+            $coroutine->when(function ($exception, $value) use (&$invoked) {
+                $invoked = true;
+            });
+        });
+
+        $this->assertTrue($invoked);
+    }
+
+    /**
+     * @depends testYieldFailedAwaitable
+     */
+    public function testYieldConsecutiveFailed() {
+        $invoked = false;
+        Loop::execute(function () use (&$invoked) {
+            $count = 1000;
+            $awaitable = new Failure(new \Exception);
+
+            $generator = function () use ($count, $awaitable) {
+                for ($i = 0; $i < $count; ++$i) {
+                    try {
+                        yield $awaitable;
+                    } catch (\Exception $exception) {
+                        // Ignore and continue.
+                    }
+                }
+            };
+
+            $coroutine = new Coroutine($generator());
+
+            $coroutine->when(function ($exception, $value) use (&$invoked) {
+                $invoked = true;
+            });
+        });
+    }
+
+    /**
+     * @depends testYieldSuccessfulAwaitable
+     */
+    public function testFastInvalidGenerator() {
+        $generator = function () {
+            if (false) {
+                yield new Success;
+            }
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $invoked = false;
+        $coroutine->when(function ($exception, $value) use (&$invoked) {
+            $invoked = true;
+        });
+
+        $this->assertTrue($invoked);
+    }
+
+    public function testCoroutineFunction() {
+        $callable = Amp\coroutine(function () {
+            yield;
+        });
+
+        $this->assertInstanceOf(Coroutine::class, $callable());
+    }
+
+    /**
+     * @depends testCoroutineFunction
+     * @expectedException \LogicException
+     */
+    public function testCoroutineFunctionWithNonGeneratorCallback() {
+        $callable = Amp\coroutine(function () {});
+
+        $this->assertInstanceOf(Coroutine::class, $callable());
+    }
+}
diff --git a/test/DeferredTest.php b/test/DeferredTest.php
new file mode 100644
index 0000000..647f6a8
--- /dev/null
+++ b/test/DeferredTest.php
@@ -0,0 +1,60 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp\Deferred;
+use Interop\Async\Awaitable;
+
+class DeferredTest extends \PHPUnit_Framework_TestCase {
+    /**
+     * @var \Amp\Deferred
+     */
+    private $deferred;
+
+    public function setUp() {
+        $this->deferred = new Deferred;
+    }
+
+    public function testGetAwaitable() {
+        $awaitable = $this->deferred->getAwaitable();
+        $this->assertInstanceOf(Awaitable::class, $awaitable);
+    }
+    
+    /**
+     * @depends testGetAwaitable
+     */
+    public function testResolve() {
+        $value = "Resolution value";
+        $awaitable = $this->deferred->getAwaitable();
+
+        $invoked = false;
+        $awaitable->when(function ($exception, $value) use (&$invoked, &$result) {
+            $invoked = true;
+            $result = $value;
+        });
+        
+        $this->deferred->resolve($value);
+
+        $this->assertTrue($invoked);
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testGetAwaitable
+     */
+    public function testFail() {
+        $exception = new \Exception;
+        $awaitable = $this->deferred->getAwaitable();
+
+        $invoked = false;
+        $awaitable->when(function ($exception, $value) use (&$invoked, &$result) {
+            $invoked = true;
+            $result = $exception;
+        });
+
+        $this->deferred->fail($exception);
+
+        $this->assertTrue($invoked);
+        $this->assertSame($exception, $result);
+    }
+}
diff --git a/test/ExtendedCoroutineTest.php b/test/ExtendedCoroutineTest.php
new file mode 100644
index 0000000..39ce7e4
--- /dev/null
+++ b/test/ExtendedCoroutineTest.php
@@ -0,0 +1,80 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp\Coroutine;
+use Amp\Success;
+
+/**
+ * @todo Combine with CoroutineTest once PHP 7 is required.
+ */
+class ExtendedCoroutineTest extends \PHPUnit_Framework_TestCase {
+    public function testCoroutineResolvedWithReturn() {
+        $value = 1;
+
+        $generator = function () use ($value) {
+            return $value;
+            yield; // Unreachable, but makes function a coroutine.
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testCoroutineResolvedWithReturn
+     */
+    public function testYieldFromGenerator() {
+        $value = 1;
+
+        $generator = function () use ($value) {
+            $generator = function () use ($value) {
+                return yield new Success($value);
+            };
+
+            return yield from $generator();
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testCoroutineResolvedWithReturn
+     */
+    public function testFastReturningGenerator()
+    {
+        $value = 1;
+
+        $generator = function () use ($value) {
+            if (true) {
+                return $value;
+            }
+
+            yield;
+
+            return -$value;
+        };
+
+        $coroutine = new Coroutine($generator());
+
+        $coroutine->when(function ($exception, $value) use (&$result) {
+            $result = $value;
+        });
+
+        $this->assertSame($value, $result);
+    }
+
+}
\ No newline at end of file
diff --git a/test/FailureTest.php b/test/FailureTest.php
new file mode 100644
index 0000000..61b9708
--- /dev/null
+++ b/test/FailureTest.php
@@ -0,0 +1,57 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp\Failure;
+use Interop\Async\Loop;
+
+class FailureTest extends \PHPUnit_Framework_TestCase {
+    /**
+     * @expectedException \LogicException
+     */
+    public function testConstructWithNonException() {
+        $failure = new Failure(1);
+    }
+
+    public function testWhen() {
+        $exception = new \Exception;
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$reason) {
+            ++$invoked;
+            $reason = $exception;
+        };
+
+        $success = new Failure($exception);
+
+        $success->when($callback);
+
+        $this->assertSame(1, $invoked);
+        $this->assertSame($exception, $reason);
+    }
+
+    /**
+     * @depends testWhen
+     */
+    public function testWhenThrowingForwardsToLoopHandlerOnSuccess() {
+        Loop::execute(function () use (&$invoked) {
+            $invoked = 0;
+            $expected = new \Exception;
+
+            Loop::setErrorHandler(function ($exception) use (&$invoked, $expected) {
+                ++$invoked;
+                $this->assertSame($expected, $exception);
+            });
+
+            $callback = function () use ($expected) {
+                throw $expected;
+            };
+
+            $success = new Failure(new \Exception);
+
+            $success->when($callback);
+        });
+
+        $this->assertSame(1, $invoked);
+    }
+}
diff --git a/test/FutureTest.php b/test/FutureTest.php
new file mode 100644
index 0000000..c8eb7e4
--- /dev/null
+++ b/test/FutureTest.php
@@ -0,0 +1,312 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp\Future;
+use Interop\Async\Awaitable;
+use Interop\Async\Loop;
+
+class FutureTest extends \PHPUnit_Framework_TestCase {
+    /**
+     * @var \Amp\Future
+     */
+    private $future;
+
+    public function setUp() {
+        $this->future = new Future;
+    }
+
+    public function testWhenOnSuccess() {
+        $value = "Resolution value";
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $value;
+        };
+
+        $this->future->when($callback);
+
+        $this->future->resolve($value);
+
+        $this->assertSame(1, $invoked);
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testWhenOnSuccess
+     */
+    public function testMultipleWhensOnSuccess() {
+        $value = "Resolution value";
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $value;
+        };
+
+        $this->future->when($callback);
+        $this->future->when($callback);
+        $this->future->when($callback);
+
+        $this->future->resolve($value);
+
+        $this->assertSame(3, $invoked);
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testWhenOnSuccess
+     */
+    public function testWhenAfterSuccess() {
+        $value = "Resolution value";
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $value;
+        };
+
+        $this->future->resolve($value);
+
+        $this->future->when($callback);
+
+        $this->assertSame(1, $invoked);
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testWhenAfterSuccess
+     */
+    public function testMultipleWhenAfterSuccess() {
+        $value = "Resolution value";
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $value;
+        };
+
+        $this->future->resolve($value);
+
+        $this->future->when($callback);
+        $this->future->when($callback);
+        $this->future->when($callback);
+
+        $this->assertSame(3, $invoked);
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testWhenOnSuccess
+     */
+    public function testWhenThrowingForwardsToLoopHandlerOnSuccess() {
+        Loop::execute(function () use (&$invoked) {
+            $invoked = 0;
+            $expected = new \Exception;
+
+            Loop::setErrorHandler(function ($exception) use (&$invoked, $expected) {
+                ++$invoked;
+                $this->assertSame($expected, $exception);
+            });
+
+            $callback = function () use ($expected) {
+                throw $expected;
+            };
+
+            $this->future->when($callback);
+
+            $this->future->resolve($expected);
+        });
+
+        $this->assertSame(1, $invoked);
+    }
+
+    /**
+     * @depends testWhenAfterSuccess
+     */
+    public function testWhenThrowingForwardsToLoopHandlerAfterSuccess() {
+        Loop::execute(function () use (&$invoked) {
+            $invoked = 0;
+            $expected = new \Exception;
+
+            Loop::setErrorHandler(function ($exception) use (&$invoked, $expected) {
+                ++$invoked;
+                $this->assertSame($expected, $exception);
+            });
+
+            $callback = function () use ($expected) {
+                throw $expected;
+            };
+
+            $this->future->resolve($expected);
+
+            $this->future->when($callback);
+        });
+
+        $this->assertSame(1, $invoked);
+    }
+
+    public function testWhenOnFail() {
+        $exception = new \Exception;
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $exception;
+        };
+
+        $this->future->when($callback);
+
+        $this->future->fail($exception);
+
+        $this->assertSame(1, $invoked);
+        $this->assertSame($exception, $result);
+    }
+
+    /**
+     * @depends testWhenOnFail
+     */
+    public function testMultipleWhensOnFail() {
+        $exception = new \Exception;
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $exception;
+        };
+
+        $this->future->when($callback);
+        $this->future->when($callback);
+        $this->future->when($callback);
+
+        $this->future->fail($exception);
+
+        $this->assertSame(3, $invoked);
+        $this->assertSame($exception, $result);
+    }
+
+    /**
+     * @depends testWhenOnFail
+     */
+    public function testWhenAfterFail() {
+        $exception = new \Exception;
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $exception;
+        };
+
+        $this->future->fail($exception);
+
+        $this->future->when($callback);
+
+        $this->assertSame(1, $invoked);
+        $this->assertSame($exception, $result);
+    }
+
+    /**
+     * @depends testWhenAfterFail
+     */
+    public function testMultipleWhensAfterFail() {
+        $exception = new \Exception;
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $exception;
+        };
+
+        $this->future->fail($exception);
+
+        $this->future->when($callback);
+        $this->future->when($callback);
+        $this->future->when($callback);
+
+        $this->assertSame(3, $invoked);
+        $this->assertSame($exception, $result);
+    }
+
+    /**
+     * @depends testWhenOnSuccess
+     */
+    public function testWhenThrowingForwardsToLoopHandlerOnFail() {
+        Loop::execute(function () use (&$invoked) {
+            $invoked = 0;
+            $expected = new \Exception;
+
+            Loop::setErrorHandler(function ($exception) use (&$invoked, $expected) {
+                ++$invoked;
+                $this->assertSame($expected, $exception);
+            });
+
+            $callback = function () use ($expected) {
+                throw $expected;
+            };
+
+            $this->future->when($callback);
+
+            $this->future->fail(new \Exception);
+        });
+
+        $this->assertSame(1, $invoked);
+    }
+
+    /**
+     * @depends testWhenOnSuccess
+     */
+    public function testWhenThrowingForwardsToLoopHandlerAfterFail() {
+        Loop::execute(function () use (&$invoked) {
+            $invoked = 0;
+            $expected = new \Exception;
+
+            Loop::setErrorHandler(function ($exception) use (&$invoked, $expected) {
+                ++$invoked;
+                $this->assertSame($expected, $exception);
+            });
+
+            $callback = function () use ($expected) {
+                throw $expected;
+            };
+
+            $this->future->fail(new \Exception);
+
+            $this->future->when($callback);
+        });
+
+        $this->assertSame(1, $invoked);
+    }
+
+    public function testResolveWithAwaitableBeforeWhen() {
+        $awaitable = $this->getMockBuilder(Awaitable::class)->getMock();
+
+        $awaitable->expects($this->once())
+            ->method("when")
+            ->with($this->callback("is_callable"));
+
+        $this->future->resolve($awaitable);
+
+        $this->future->when(function () {});
+    }
+
+    public function testResolveWithAwaitableAfterWhen() {
+        $awaitable = $this->getMockBuilder(Awaitable::class)->getMock();
+
+        $awaitable->expects($this->once())
+            ->method("when")
+            ->with($this->callback("is_callable"));
+
+        $this->future->when(function () {});
+
+        $this->future->resolve($awaitable);
+    }
+
+    /**
+     * @expectedException \LogicException
+     */
+    public function testDoubleResolve() {
+        $this->future->resolve();
+        $this->future->resolve();
+    }
+}
diff --git a/test/PipeTest.php b/test/PipeTest.php
new file mode 100644
index 0000000..bfff9a5
--- /dev/null
+++ b/test/PipeTest.php
@@ -0,0 +1,84 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Amp\Success;
+use Interop\Async\Awaitable;
+
+class PipeTest extends \PHPUnit_Framework_TestCase {
+    public function testSuccessfulAwaitable() {
+        $invoked = false;
+        $callback = function ($value) use (&$invoked) {
+            $invoked = true;
+            return $value + 1;
+        };
+
+        $value = 1;
+
+        $awaitable = new Success($value);
+
+        $awaitable = Amp\pipe($awaitable, $callback);
+        $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        $awaitable->when($callback);
+
+        $this->assertTrue($invoked);
+        $this->assertSame($value + 1, $result);
+    }
+
+    public function testFailedAwaitable() {
+        $invoked = false;
+        $callback = function ($value) use (&$invoked) {
+            $invoked = true;
+            return $value + 1;
+        };
+
+        $exception = new \Exception;
+
+        $awaitable = new Failure($exception);
+
+        $awaitable = Amp\pipe($awaitable, $callback);
+        $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+        $callback = function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        };
+
+        $awaitable->when($callback);
+
+        $this->assertFalse($invoked);
+        $this->assertSame($exception, $reason);
+    }
+    
+    /**
+     * @depends testSuccessfulAwaitable
+     */
+    public function testCallbackThrowing() {
+        $exception = new \Exception;
+        $callback = function ($value) use (&$invoked, $exception) {
+            $invoked = true;
+            throw $exception;
+        };
+    
+        $value = 1;
+    
+        $awaitable = new Success($value);
+    
+        $awaitable = Amp\pipe($awaitable, $callback);
+    
+        $callback = function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        };
+    
+        $awaitable->when($callback);
+    
+        $this->assertTrue($invoked);
+        $this->assertSame($exception, $reason);
+    }
+}
diff --git a/test/RethrowTest.php b/test/RethrowTest.php
new file mode 100644
index 0000000..5df7fc5
--- /dev/null
+++ b/test/RethrowTest.php
@@ -0,0 +1,26 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Interop\Async\Loop;
+
+class RethrowTest extends \PHPUnit_Framework_TestCase {
+    public function testWaitOnPendingAwaitable() {
+        $exception = new \Exception;
+
+        try {
+            Loop::execute(function () use ($exception) {
+                $awaitable = new Failure($exception);
+
+                Amp\rethrow($awaitable);
+            });
+        } catch (\Exception $reason) {
+            $this->assertSame($exception, $reason);
+            return;
+        }
+
+        $this->fail('Failed awaitable reason should be thrown from loop');
+    }
+}
diff --git a/test/SomeTest.php b/test/SomeTest.php
new file mode 100644
index 0000000..9a58236
--- /dev/null
+++ b/test/SomeTest.php
@@ -0,0 +1,106 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Amp\MultiReasonException;
+use Amp\Pause;
+use Amp\Success;
+use Interop\Async\Loop;
+
+class SomeTest extends \PHPUnit_Framework_TestCase {
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function testEmptyArray() {
+        Amp\some([], 1);
+    }
+
+    public function testSuccessfulAwaitablesArray() {
+        $awaitables = [new Success(1), new Success(2), new Success(3)];
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        Amp\some($awaitables, 2)->when($callback);
+
+        $this->assertSame([1, 2], $result);
+    }
+
+    public function testSuccessfulAndFailedAwaitablesArray() {
+        $awaitables = [new Failure(new \Exception), new Failure(new \Exception), new Success(3)];
+
+        $callback = function ($exception, $value) use (&$result) {
+            $result = $value;
+        };
+
+        Amp\some($awaitables, 1)->when($callback);
+
+        $this->assertSame([2 => 3], $result);
+    }
+
+    public function testTooManyFailedAwaitables() {
+        $awaitables = [new Failure(new \Exception), new Failure(new \Exception), new Success(3)];
+
+        $callback = function ($exception, $value) use (&$reason) {
+            $reason = $exception;
+        };
+
+        Amp\some($awaitables, 2)->when($callback);
+
+        $this->assertInstanceOf(MultiReasonException::class, $reason);
+
+        $reasons = $reason->getReasons();
+
+        foreach ($reasons as $reason) {
+            $this->assertInstanceOf(\Exception::class, $reason);
+        }
+    }
+
+    public function testPendingAwatiablesArray() {
+        Loop::execute(function () use (&$result) {
+            $awaitables = [
+                new Pause(0.2, 1),
+                new Pause(0.3, 2),
+                new Pause(0.1, 3),
+            ];
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            Amp\some($awaitables, 2)->when($callback);
+        });
+
+        $this->assertEquals([0 => 1, 2 => 3], $result);
+    }
+
+    public function testArrayKeysPreserved() {
+        $expected = ['one' => 1, 'two' => 2, 'three' => 3];
+
+        Loop::execute(function () use (&$result) {
+            $awaitables = [
+                'one'   => new Pause(0.2, 1),
+                'two'   => new Pause(0.3, 2),
+                'three' => new Pause(0.1, 3),
+            ];
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            Amp\some($awaitables, 3)->when($callback);
+        });
+
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function testNonAwaitable() {
+        Amp\some([1], 1);
+    }
+}
diff --git a/test/SuccessTest.php b/test/SuccessTest.php
new file mode 100644
index 0000000..5af7802
--- /dev/null
+++ b/test/SuccessTest.php
@@ -0,0 +1,58 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp\Success;
+use Interop\Async\Awaitable;
+use Interop\Async\Loop;
+
+class SuccessTest extends \PHPUnit_Framework_TestCase {
+    /**
+     * @expectedException \LogicException
+     */
+    public function testConstructWithNonException() {
+        $failure = new Success($this->getMockBuilder(Awaitable::class)->getMock());
+    }
+
+    public function testWhen() {
+        $value = "Resolution value";
+
+        $invoked = 0;
+        $callback = function ($exception, $value) use (&$invoked, &$result) {
+            ++$invoked;
+            $result = $value;
+        };
+
+        $success = new Success($value);
+
+        $success->when($callback);
+
+        $this->assertSame(1, $invoked);
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testWhen
+     */
+    public function testWhenThrowingForwardsToLoopHandlerOnSuccess() {
+        Loop::execute(function () use (&$invoked) {
+            $invoked = 0;
+            $expected = new \Exception;
+
+            Loop::setErrorHandler(function ($exception) use (&$invoked, $expected) {
+                ++$invoked;
+                $this->assertSame($expected, $exception);
+            });
+
+            $callback = function () use ($expected) {
+                throw $expected;
+            };
+
+            $success = new Success;
+
+            $success->when($callback);
+        });
+
+        $this->assertSame(1, $invoked);
+    }
+}
diff --git a/test/TimeoutTest.php b/test/TimeoutTest.php
new file mode 100644
index 0000000..f78438c
--- /dev/null
+++ b/test/TimeoutTest.php
@@ -0,0 +1,92 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Amp\Pause;
+use Amp\Success;
+use Interop\Async\Awaitable;
+use Interop\Async\Loop;
+
+class TimeoutTest extends \PHPUnit_Framework_TestCase {
+    public function testSuccessfulAwaitable() {
+        Loop::execute(function () {
+            $value = 1;
+
+            $awaitable = new Success($value);
+
+            $awaitable = Amp\timeout($awaitable, 100);
+            $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            $awaitable->when($callback);
+
+            $this->assertSame($value, $result);
+        });
+    }
+
+    public function testFailedAwaitable() {
+        Loop::execute(function () {
+            $exception = new \Exception;
+
+            $awaitable = new Failure($exception);
+
+            $awaitable = Amp\timeout($awaitable, 100);
+            $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+            $callback = function ($exception, $value) use (&$reason) {
+                $reason = $exception;
+            };
+
+            $awaitable->when($callback);
+
+            $this->assertSame($exception, $reason);
+        });
+    }
+    
+    /**
+     * @depends testSuccessfulAwaitable
+     */
+    public function testFastPending() {
+        $value = 1;
+
+        Loop::execute(function () use (&$result, $value) {
+            $awaitable = new Pause(50, $value);
+
+            $awaitable = Amp\timeout($awaitable, 100);
+            $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+            $callback = function ($exception, $value) use (&$result) {
+                $result = $value;
+            };
+
+            $awaitable->when($callback);
+        });
+
+        $this->assertSame($value, $result);
+    }
+
+    /**
+     * @depends testSuccessfulAwaitable
+     */
+    public function testSlowPending() {
+        Loop::execute(function () use (&$reason) {
+            $awaitable = new Pause(200);
+
+            $awaitable = Amp\timeout($awaitable, 100);
+            $this->assertInstanceOf(Awaitable::class, $awaitable);
+
+            $callback = function ($exception, $value) use (&$reason) {
+                $reason = $exception;
+            };
+
+            $awaitable->when($callback);
+        });
+
+        $this->assertInstanceOf(Amp\TimeoutException::class, $reason);
+    }
+}
diff --git a/test/WaitTest.php b/test/WaitTest.php
new file mode 100644
index 0000000..d8bd765
--- /dev/null
+++ b/test/WaitTest.php
@@ -0,0 +1,65 @@
+<?php
+
+namespace Amp\Test;
+
+use Amp;
+use Amp\Failure;
+use Amp\Future;
+use Amp\Pause;
+use Amp\Success;
+use Interop\Async\Loop;
+
+class WaitTest extends \PHPUnit_Framework_TestCase {
+    public function testWaitOnSuccessfulAwaitable()
+    {
+        $value = 1;
+
+        $awaitable = new Success($value);
+
+        $result = Amp\wait($awaitable);
+
+        $this->assertSame($value, $result);
+    }
+
+    public function testWaitOnFailedAwaitable()
+    {
+        $exception = new \Exception();
+
+        $awaitable = new Failure($exception);
+
+        try {
+            $result = Amp\wait($awaitable);
+        } catch (\Exception $e) {
+            $this->assertSame($exception, $e);
+            return;
+        }
+
+        $this->fail('Rejection exception should be thrown from wait().');
+    }
+
+    /**
+     * @depends testWaitOnSuccessfulAwaitable
+     */
+    public function testWaitOnPendingAwaitable()
+    {
+        Loop::execute(function () {
+            $value = 1;
+
+            $awaitable = new Pause(100, $value);
+
+            $result = Amp\wait($awaitable);
+
+            $this->assertSame($value, $result);
+        });
+    }
+
+    /**
+     * @expectedException \LogicException
+     */
+    public function testAwaitableWithNoResolutionPathThrowsException()
+    {
+        $awaitable = new Future;
+
+        $result = Amp\wait($awaitable);
+    }
+}