Run tests on PHPUnit 9 and clean up test suite

.travis.yml

@@ -16,7 +16,6 @@ matrix:
     - php: 7.3
     - php: 7.4
     - php: hhvm-3.18
-      install: composer require phpunit/phpunit:^5 --dev --no-interaction # requires legacy phpunit
   allow_failures:
     - php: hhvm-3.18
 

composer.json

@@ -23,6 +23,6 @@
         "react/promise": "^3.0 || ^2.7.0 || ^1.2.1"
     },
     "require-dev": {
-        "phpunit/phpunit": "^7.0 || ^6.4 || ^5.7 || ^4.8.35"
+        "phpunit/phpunit": "^9.0 || ^5.7 || ^4.8.35"
     }
 }

phpunit.xml.dist

@@ -1,11 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 
-<phpunit bootstrap="vendor/autoload.php"
-         colors="true"
-         convertErrorsToExceptions="true"
-         convertNoticesToExceptions="true"
-         convertWarningsToExceptions="true"
->
+<phpunit bootstrap="vendor/autoload.php" colors="true">
     <testsuites>
         <testsuite name="Promise Timer Test Suite">
             <directory>./tests/</directory>

tests/TestCase.php

@@ -9,7 +9,10 @@ class TestCase extends BaseTestCase
 {
     protected $loop;
 
-    public function setUp()
+    /**
+     * @before
+     */
+    public function setUpLoop()
     {
         $this->loop = Factory::create();
     }
@@ -41,7 +44,13 @@ protected function expectCallableNever()
      */
     protected function createCallableMock()
     {
-        return $this->getMockBuilder('React\Tests\Promise\Timer\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();
+        }
     }
 
     protected function expectPromiseRejected($promise)