diff --git a/.travis.yml b/.travis.yml
index 3464291..ff544ca 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,12 +1,24 @@
 language: php
 
 php:
-  - 5.3
+# - 5.3 # requires old distro
   - 5.4
   - 5.5
   - 5.6
-  - 7
-  - hhvm
+  - 7.0
+  - 7.1
+  - 7.2
+  - hhvm # ignore errors, see below
+
+# lock distro so new future defaults will not break the build
+dist: trusty
+
+matrix:
+  include:
+    - php: 5.3
+      dist: precise
+  allow_failures:
+    - php: hhvm
 
 sudo: false
 
@@ -14,4 +26,4 @@ install:
   - composer install --no-interaction
 
 script:
-  - phpunit --coverage-text
+  - vendor/bin/phpunit --coverage-text
diff --git a/README.md b/README.md
index 9897d82..2d2b095 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,7 @@ enriched with the comfort of [React PHP's Promises/A](https://github.com/reactph
     * [getName()](#getname)
     * [getDescription()](#getdescription)
 * [Install](#install)
+* [Tests](#tests)
 * [License](#license)
 
 ## Quickstart example
@@ -137,6 +138,21 @@ $ composer require clue/packagist-api-react:^1.1
 
 See also the [CHANGELOG](CHANGELOG.md) for details about version upgrades.
 
+## Tests
+
+To run the test suite, you first need to clone this repo and then install all
+dependencies [through Composer](https://getcomposer.org):
+
+```bash
+$ composer install
+```
+
+To run the test suite, go to the project root and run:
+
+```bash
+$ php vendor/bin/phpunit
+```
+
 ## License
 
 MIT
diff --git a/composer.json b/composer.json
index d75d916..dee2d0c 100644
--- a/composer.json
+++ b/composer.json
@@ -16,6 +16,9 @@
         "clue/buzz-react": "^1.0 || ^0.5",
         "rize/uri-template": "^0.3"
     },
+    "require-dev": {
+        "phpunit/phpunit": "^6.0 || ^5.7 || ^4.8.35"
+    },
     "autoload": {
         "psr-4": { "Clue\\React\\Packagist\\Api\\": "src/" }
     }
diff --git a/tests/ClientTest.php b/tests/ClientTest.php
index 6e114d0..521489e 100644
--- a/tests/ClientTest.php
+++ b/tests/ClientTest.php
@@ -82,7 +82,7 @@ private function setupBrowser($expectedUrl, $promise)
 
     private function createResponsePromise($fakeResponseBody)
     {
-        $response = $this->getMock('Psr\Http\Message\ResponseInterface');
+        $response = $this->getMockBuilder('Psr\Http\Message\ResponseInterface')->getMock();
         $response->expects($this->once())->method('getBody')->willReturn($fakeResponseBody);
 
         return Promise\resolve($response);
diff --git a/tests/bootstrap.php b/tests/bootstrap.php
index 7c67587..f9aeee5 100644
--- a/tests/bootstrap.php
+++ b/tests/bootstrap.php
@@ -1,8 +1,10 @@
 <?php
 
+use PHPUnit\Framework\TestCase as BaseTestCase;
+
 require_once __DIR__ . '/../vendor/autoload.php';
 
-class TestCase extends PHPUnit_Framework_TestCase
+class TestCase extends BaseTestCase
 {
     protected function expectCallableOnce()
     {
@@ -44,12 +46,9 @@ protected function expectCallableOnceParameter($type)
         return $mock;
     }
 
-    /**
-     * @link https://github.com/reactphp/react/blob/master/tests/React/Tests/Socket/TestCase.php (taken from reactphp/react)
-     */
     protected function createCallableMock()
     {
-        return $this->getMock('CallableStub');
+        return $this->getMockBuilder('stdClass')->setMethods(array('__invoke'))->getMock();
     }
 
     protected function expectPromiseResolve($promise)
@@ -70,11 +69,3 @@ protected function expectPromiseReject($promise)
         return $promise;
     }
 }
-
-class CallableStub
-{
-    public function __invoke()
-    {
-    }
-}
-