diff --git a/.gitattributes b/.gitattributes
new file mode 100644
index 00000000..0925d33a
--- /dev/null
+++ b/.gitattributes
@@ -0,0 +1,6 @@
+/.gitattributes export-ignore
+/.gitignore export-ignore
+/.travis.yml export-ignore
+/examples/ export-ignore
+/phpunit.xml.dist export-ignore
+/tests/ export-ignore
diff --git a/.travis.yml b/.travis.yml
index eb5a9cdc..e1421bc6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,18 +1,26 @@
 language: php
 
-php:
-  - 5.3
-  - 5.4
-  - 5.5
-  - 5.6
-  - 7.0
-  - hhvm
+# lock distro so new future defaults will not break the build
+dist: trusty
 
-before_install:
-  - composer self-update
+jobs:
+  include:
+    - php: 5.3
+      dist: precise
+    - php: 5.4
+    - php: 5.5
+    - php: 5.6
+    - php: 7.0
+    - php: 7.1
+    - php: 7.2
+    - php: 7.3
+    - php: 7.4
+    - php: hhvm-3.18
+  allow_failures:
+    - php: hhvm-3.18
 
 install:
-  - composer install --prefer-source
+  - composer install
 
 script:
-  - phpunit -v --coverage-text
+  - vendor/bin/phpunit --coverage-text
diff --git a/composer.json b/composer.json
index 7e1caffb..2e1f1cd8 100644
--- a/composer.json
+++ b/composer.json
@@ -8,12 +8,20 @@
     "require": {
         "php": ">=5.3.3"
     },
+    "require-dev": {
+        "phpunit/phpunit": "^9.0 || ^5.7 || ^4.8.35"
+    },
     "autoload": {
-        "psr-0": {
-            "React\\Promise": "src/"
+        "psr-4": { 
+            "React\\Promise\\": "src/React/Promise/" 
         },
         "files": ["src/React/Promise/functions_include.php"]
     },
+    "autoload-dev": {
+        "psr-4": {
+            "React\\Tests\\Promise\\": "tests/React/Promise/" 
+        }
+    },
     "extra": {
         "branch-alias": {
             "dev-master": "1.1-dev"
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index 0f98aea7..8ce12cfa 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -1,16 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit backupGlobals="false"
-         backupStaticAttributes="false"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="false"
-         convertWarningsToExceptions="true"
-         processIsolation="false"
-         stopOnFailure="false"
-         syntaxCheck="false"
-         bootstrap="tests/bootstrap.php"
->
+<phpunit bootstrap="vendor/autoload.php" colors="true">
     <testsuites>
         <testsuite name="Promise Test Suite">
             <directory>./tests/React/Promise/</directory>
diff --git a/tests/React/Promise/DeferredProgressTest.php b/tests/React/Promise/DeferredProgressTest.php
index 838105da..44875781 100644
--- a/tests/React/Promise/DeferredProgressTest.php
+++ b/tests/React/Promise/DeferredProgressTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
 
 /**
  * @group Deferred
diff --git a/tests/React/Promise/DeferredPromiseTest.php b/tests/React/Promise/DeferredPromiseTest.php
index 22f34b71..b087e1dd 100644
--- a/tests/React/Promise/DeferredPromiseTest.php
+++ b/tests/React/Promise/DeferredPromiseTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\DeferredPromise;
 
 /**
  * @group Promise
diff --git a/tests/React/Promise/DeferredRejectTest.php b/tests/React/Promise/DeferredRejectTest.php
index f10d9beb..d59537e4 100644
--- a/tests/React/Promise/DeferredRejectTest.php
+++ b/tests/React/Promise/DeferredRejectTest.php
@@ -1,6 +1,10 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\FulfilledPromise;
+use React\Promise\RejectedPromise;
 
 /**
  * @group Deferred
diff --git a/tests/React/Promise/DeferredResolveTest.php b/tests/React/Promise/DeferredResolveTest.php
index 3ee7027c..55783d62 100644
--- a/tests/React/Promise/DeferredResolveTest.php
+++ b/tests/React/Promise/DeferredResolveTest.php
@@ -1,6 +1,11 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\FulfilledPromise;
+use React\Promise\RejectedPromise;
+use React\Promise\When;
 
 /**
  * @group Deferred
diff --git a/tests/React/Promise/DeferredResolverTest.php b/tests/React/Promise/DeferredResolverTest.php
index 2ee55f12..2eb1442a 100644
--- a/tests/React/Promise/DeferredResolverTest.php
+++ b/tests/React/Promise/DeferredResolverTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\DeferredResolver;
 
 /**
  * @group Resolver
diff --git a/tests/React/Promise/DeferredTest.php b/tests/React/Promise/DeferredTest.php
index b5c2fdba..4cd6f6b7 100644
--- a/tests/React/Promise/DeferredTest.php
+++ b/tests/React/Promise/DeferredTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
 
 /**
  * @group Deferred
@@ -204,10 +206,10 @@ public function shouldInvokeCancellationHandleWhenCancellingAllDerived()
 
     /**
      * @test
-     * @expectedException InvalidArgumentException
      */
     public function shouldThrowIfCancellerIsNotACallable()
     {
+        $this->setExpectedException('InvalidArgumentException');
         new Deferred(false);
     }
 }
diff --git a/tests/React/Promise/ErrorCollector.php b/tests/React/Promise/ErrorCollector.php
index 648ab68a..dcc21946 100644
--- a/tests/React/Promise/ErrorCollector.php
+++ b/tests/React/Promise/ErrorCollector.php
@@ -1,6 +1,6 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
 
 class ErrorCollector
 {
@@ -33,6 +33,6 @@ public function assertCollectedError($errstr, $errno)
 
         $message = 'Error with level ' . $errno . ' and message "' . $errstr . '" not found in ' . var_export($this->errors, true);
 
-        throw new \PHPUnit_Framework_AssertionFailedError($message);
+        throw new \PHPUnit\Framework\AssertionFailedError($message);
     }
 }
diff --git a/tests/React/Promise/FulfilledPromiseTest.php b/tests/React/Promise/FulfilledPromiseTest.php
index fb1fafce..13777258 100644
--- a/tests/React/Promise/FulfilledPromiseTest.php
+++ b/tests/React/Promise/FulfilledPromiseTest.php
@@ -1,6 +1,9 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\FulfilledPromise;
+use React\Promise\RejectedPromise;
 
 /**
  * @group Promise
diff --git a/tests/React/Promise/LazyPromiseTest.php b/tests/React/Promise/LazyPromiseTest.php
index 577d24b3..a03cf0f2 100644
--- a/tests/React/Promise/LazyPromiseTest.php
+++ b/tests/React/Promise/LazyPromiseTest.php
@@ -1,6 +1,10 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\FulfilledPromise;
+use React\Promise\LazyPromise;
 
 /**
  * @group Promise
diff --git a/tests/React/Promise/PromiseTest.php b/tests/React/Promise/PromiseTest.php
index e6f22fbd..9942e468 100644
--- a/tests/React/Promise/PromiseTest.php
+++ b/tests/React/Promise/PromiseTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Promise;
 
 /**
  * @group Promise
@@ -10,7 +12,7 @@ class PromiseTest extends TestCase
     /** @test */
     public function shouldThrowIfResolverIsNotACallable()
     {
-        $this->setExpectedException('\InvalidArgumentException');
+        $this->setExpectedException('InvalidArgumentException');
 
         new Promise(null);
     }
@@ -93,10 +95,10 @@ public function shouldInvokeCancellationHandlerAndStayPendingWhenCallingCancel()
 
     /**
      * @test
-     * @expectedException InvalidArgumentException
      */
     public function shouldThrowIfCancellerIsNotACallable()
     {
+        $this->setExpectedException('InvalidArgumentException');
         new Promise(function () { }, false);
     }
 }
diff --git a/tests/React/Promise/RejectedPromiseTest.php b/tests/React/Promise/RejectedPromiseTest.php
index d2cb860f..1b5dc84c 100644
--- a/tests/React/Promise/RejectedPromiseTest.php
+++ b/tests/React/Promise/RejectedPromiseTest.php
@@ -1,6 +1,9 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\FulfilledPromise;
+use React\Promise\RejectedPromise;
 
 /**
  * @group Promise
diff --git a/tests/React/Promise/Stub/CallableStub.php b/tests/React/Promise/Stub/CallableStub.php
deleted file mode 100644
index 01208933..00000000
--- a/tests/React/Promise/Stub/CallableStub.php
+++ /dev/null
@@ -1,10 +0,0 @@
-<?php
-
-namespace React\Promise\Stub;
-
-class CallableStub
-{
-    public function __invoke()
-    {
-    }
-}
diff --git a/tests/React/Promise/TestCase.php b/tests/React/Promise/TestCase.php
index e7c3eb7c..47a97f4e 100644
--- a/tests/React/Promise/TestCase.php
+++ b/tests/React/Promise/TestCase.php
@@ -1,8 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
 
-class TestCase extends \PHPUnit_Framework_TestCase
+class TestCase extends \PHPUnit\Framework\TestCase
 {
     public function expectCallableExactly($amount)
     {
@@ -36,9 +36,13 @@ public function expectCallableNever()
 
     public function createCallableMock()
     {
-        return $this
-            ->getMockBuilder('React\\Promise\Stub\CallableStub')
-            ->getMock();
+        if (method_exists('PHPUnit\Framework\MockObject\MockBuilder', 'addMethods')) {
+            // PHPUnit 9+
+            return $this->getMockBuilder('stdClass')->addMethods(array('__invoke'))->getMock();
+        } else {
+            // legacy PHPUnit 4 - PHPUnit 9
+            return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
+        }
     }
 
     public function invalidCallbackDataProvider()
@@ -52,4 +56,21 @@ public function invalidCallbackDataProvider()
             'falsey'       => array(0)
         );
     }
+
+    public function setExpectedException($exception, $exceptionMessage = '', $exceptionCode = null)
+    {
+        if (method_exists($this, 'expectException')) {
+            // PHPUnit 5+
+            $this->expectException($exception);
+            if ($exceptionMessage !== '') {
+                $this->expectExceptionMessage($exceptionMessage);
+            }
+            if ($exceptionCode !== null) {
+                $this->expectExceptionCode($exceptionCode);
+            }
+        } else {
+            // legacy PHPUnit 4
+            parent::setExpectedException($exception, $exceptionMessage, $exceptionCode);
+        }
+    }
 }
diff --git a/tests/React/Promise/UtilPromiseForTest.php b/tests/React/Promise/UtilPromiseForTest.php
index cdadf2e3..49b70e77 100644
--- a/tests/React/Promise/UtilPromiseForTest.php
+++ b/tests/React/Promise/UtilPromiseForTest.php
@@ -1,6 +1,10 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\FulfilledPromise;
+use React\Promise\RejectedPromise;
+use React\Promise\Util;
 
 /**
  * @group Util
diff --git a/tests/React/Promise/UtilRejectedPromiseForTest.php b/tests/React/Promise/UtilRejectedPromiseForTest.php
index 3c2265a7..11027043 100644
--- a/tests/React/Promise/UtilRejectedPromiseForTest.php
+++ b/tests/React/Promise/UtilRejectedPromiseForTest.php
@@ -1,6 +1,10 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\FulfilledPromise;
+use React\Promise\RejectedPromise;
+use React\Promise\Util;
 
 /**
  * @group Util
diff --git a/tests/React/Promise/WhenAllTest.php b/tests/React/Promise/WhenAllTest.php
index 555eb382..6961f355 100644
--- a/tests/React/Promise/WhenAllTest.php
+++ b/tests/React/Promise/WhenAllTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenAnyTest.php b/tests/React/Promise/WhenAnyTest.php
index 467fec1a..3d193195 100644
--- a/tests/React/Promise/WhenAnyTest.php
+++ b/tests/React/Promise/WhenAnyTest.php
@@ -1,6 +1,9 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenLazyTest.php b/tests/React/Promise/WhenLazyTest.php
index a6512388..0610cc4c 100644
--- a/tests/React/Promise/WhenLazyTest.php
+++ b/tests/React/Promise/WhenLazyTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenMapTest.php b/tests/React/Promise/WhenMapTest.php
index 9dfc88a9..356ab0bd 100644
--- a/tests/React/Promise/WhenMapTest.php
+++ b/tests/React/Promise/WhenMapTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenReduceTest.php b/tests/React/Promise/WhenReduceTest.php
index 425019f9..be606ad2 100644
--- a/tests/React/Promise/WhenReduceTest.php
+++ b/tests/React/Promise/WhenReduceTest.php
@@ -1,6 +1,9 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenRejectTest.php b/tests/React/Promise/WhenRejectTest.php
index 1116eabd..77ededac 100644
--- a/tests/React/Promise/WhenRejectTest.php
+++ b/tests/React/Promise/WhenRejectTest.php
@@ -1,6 +1,9 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenResolveTest.php b/tests/React/Promise/WhenResolveTest.php
index ab591423..c74141da 100644
--- a/tests/React/Promise/WhenResolveTest.php
+++ b/tests/React/Promise/WhenResolveTest.php
@@ -1,6 +1,9 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\Deferred;
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/React/Promise/WhenSomeTest.php b/tests/React/Promise/WhenSomeTest.php
index 9704b734..f93029cb 100644
--- a/tests/React/Promise/WhenSomeTest.php
+++ b/tests/React/Promise/WhenSomeTest.php
@@ -1,6 +1,8 @@
 <?php
 
-namespace React\Promise;
+namespace React\Tests\Promise;
+
+use React\Promise\When;
 
 /**
  * @group When
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
deleted file mode 100644
index e2333359..00000000
--- a/tests/bootstrap.php
+++ /dev/null
@@ -1,4 +0,0 @@
-<?php
-
-$loader = require __DIR__.'/../vendor/autoload.php';
-$loader->add('React\Promise', __DIR__);