Add PHPUnit and use GitHub actions for continuous integration (CI)

Author: clue

.github/workflows/ci.yml

@@ -0,0 +1,29 @@
+name: CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  PHPUnit:
+    name: PHPUnit (PHP ${{ matrix.php }})
+    runs-on: ubuntu-20.04
+    strategy:
+      matrix:
+        php:
+          - 7.4
+          - 7.3
+          - 7.2
+          - 7.1
+          - 5.6
+          - 5.5
+          - 5.4
+          - 5.3
+    steps:
+      - uses: actions/checkout@v2
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: xdebug
+      - run: composer install
+      - run: vendor/bin/phpunit --coverage-text

.gitignore

@@ -1 +1,2 @@
-vendor
+/composer.lock
+/vendor/

.travis.yml

@@ -6,7 +6,7 @@ Async utilities for React.
 
 It is heavily influenced by [async.js](https://github.com/caolan/async).
 
-[![Build Status](https://secure.travis-ci.org/reactphp/async.png?branch=master)](http://travis-ci.org/reactphp/async)
+[![CI status](https://github.com/reactphp/async/workflows/CI/badge.svg)](https://github.com/reactphp/async/actions)
 
 ## About
 
@@ -118,9 +118,18 @@ $loop->run();
 
 ## Tests
 
-To run the test suite, you need PHPUnit.
+To run the test suite, you first need to clone this repo and then install all
+dependencies [through Composer](https://getcomposer.org/):
 
-    $ phpunit
+```bash
+$ composer install
+```
+
+To run the test suite, go to the project root and run:
+
+```bash
+$ php vendor/bin/phpunit
+```
 
 ## License
 

README.md

@@ -7,6 +7,7 @@
         "php": ">=5.3.2"
     },
     "require-dev": {
+        "phpunit/phpunit": "^5.7 || ^4.8.35",
         "react/event-loop": "0.2.*"
     },
     "suggest": {

composer.json

@@ -6,7 +6,7 @@ class TestCase extends \PHPUnit_Framework_TestCase
 {
     protected function createCallableMock($expects, $with = null)
     {
-        $callable = $this->getMock('React\Tests\Async\CallableStub');
+        $callable = $this->getMockBuilder('React\Tests\Async\CallableStub')->getMock();
 
         $method = $callable
             ->expects($expects)