Add checks for required libraries

src/Framework/TestResult.php

@@ -645,8 +645,7 @@ public function run(Test $test): void
         try {
             if (!$test instanceof WarningTestCase &&
                 $this->enforceTimeLimit &&
-                ($this->defaultTimeLimit || $test->getSize() != \PHPUnit\Util\Test::UNKNOWN) &&
-                \extension_loaded('pcntl') && \class_exists(Invoker::class)) {
+                ($this->defaultTimeLimit || $test->getSize() != \PHPUnit\Util\Test::UNKNOWN)) {
                 switch ($test->getSize()) {
                     case \PHPUnit\Util\Test::SMALL:
                         $_timeout = $this->timeoutForSmallTests;

src/TextUI/TestRunner.php

@@ -54,6 +54,7 @@
 use SebastianBergmann\CodeCoverage\Report\Xml\Facade as XmlReport;
 use SebastianBergmann\Comparator\Comparator;
 use SebastianBergmann\Environment\Runtime;
+use SebastianBergmann\Invoker\Invoker;
 
 /**
  * A TestRunner for the Command Line Interface (CLI)
@@ -582,6 +583,16 @@ public function doRun(Test $suite, array $arguments = [], bool $exit = true): Te
         $result->beStrictAboutOutputDuringTests($arguments['disallowTestOutput']);
         $result->beStrictAboutTodoAnnotatedTests($arguments['disallowTodoAnnotatedTests']);
         $result->beStrictAboutResourceUsageDuringSmallTests($arguments['beStrictAboutResourceUsageDuringSmallTests']);
+
+        if ($arguments['enforceTimeLimit'] === true) {
+            if (!\class_exists(Invoker::class)) {
+                $this->writeMessage('Error', 'Package phpunit/php-invoker is required for enforcing time limits');
+            }
+
+            if (!\extension_loaded('pcntl') || \strpos(\ini_get('disable_functions'), 'pcntl') !== false) {
+                $this->writeMessage('Error', 'PHP extension pcntl is required for enforcing time limits');
+            }
+        }
         $result->enforceTimeLimit($arguments['enforceTimeLimit']);
         $result->setDefaultTimeLimit($arguments['defaultTimeLimit']);
         $result->setTimeoutForSmallTests($arguments['timeoutForSmallTests']);

tests/Regression/GitHub/2085/Issue2085Test.php

@@ -0,0 +1,20 @@
+<?php
+/*
+ * This file is part of PHPUnit.
+ *
+ * (c) Sebastian Bergmann <sebastian@phpunit.de>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+use PHPUnit\Framework\TestCase;
+
+class Issue2085Test extends TestCase
+{
+    public function testShouldAbortSlowTestByEnforcingTimeLimit(): void
+    {
+        $this->assertTrue(true);
+        \sleep(2);
+        $this->assertTrue(true);
+    }
+}

tests/Regression/GitHub/2085/issue-2085-test.phpt

@@ -0,0 +1,30 @@
+--TEST--
+https://github.com/sebastianbergmann/phpunit/issues/2085
+--SKIPIF--
+<?php
+if (false || !\class_exists(Invoker::class)) {
+    print "Package phpunit/php-invoker is required for enforcing time limits");
+}
+--FILE--
+<?php
+$_SERVER['argv'][1] = '--no-configuration';
+$_SERVER['argv'][2] = '--enforce-time-limit';
+$_SERVER['argv'][3] = '--default-time-limit=1';
+$_SERVER['argv'][4] = __DIR__ . '/Issue2085Test.php';
+
+require __DIR__ . '/../../../bootstrap.php';
+PHPUnit\TextUI\Command::main();
+--EXPECTF--
+PHPUnit %s by Sebastian Bergmann and contributors.
+
+R                                                                   1 / 1 (100%)
+
+Time: %s, Memory: %s
+
+There was 1 risky test:
+
+1) Issue2085Test::testShouldAbortSlowTestByEnforcingTimeLimit
+Execution aborted after 1 second
+
+OK, but incomplete, skipped, or risky tests!
+Tests: 1, Assertions: 1, Risky: 1.