Add command testing utilities to TestCase, add tests for ConfigCommand

src/Composer/Command/ConfigCommand.php

@@ -305,7 +305,7 @@ EOT
             }
 
             if (is_array($value)) {
-                $value = json_encode($value);
+                $value = JsonFile::encode($value, JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE);
             }
 
             $sourceOfConfigValue = '';

tests/Composer/Test/Autoload/AutoloadGeneratorTest.php

@@ -91,7 +91,7 @@ class AutoloadGeneratorTest extends TestCase
     {
         $this->fs = new Filesystem;
 
-        $this->workingDir = $this->getUniqueTmpDirectory();
+        $this->workingDir = self::getUniqueTmpDirectory();
         $this->vendorDir = $this->workingDir.DIRECTORY_SEPARATOR.'composer-test-autoload';
         $this->ensureDirectoryExistsAndClear($this->vendorDir);
 

tests/Composer/Test/Autoload/ClassMapGeneratorTest.php

@@ -148,7 +148,7 @@ class ClassMapGeneratorTest extends TestCase
     {
         $this->checkIfFinderIsAvailable();
 
-        $tempDir = $this->getUniqueTmpDirectory();
+        $tempDir = self::getUniqueTmpDirectory();
         $this->ensureDirectoryExistsAndClear($tempDir . '/other');
 
         $finder = new Finder();
@@ -190,7 +190,7 @@ class ClassMapGeneratorTest extends TestCase
      */
     public function testUnambiguousReference(): void
     {
-        $tempDir = $this->getUniqueTmpDirectory();
+        $tempDir = self::getUniqueTmpDirectory();
 
         file_put_contents($tempDir . '/A.php', "<?php\nclass A {}");
         file_put_contents(

tests/Composer/Test/CacheTest.php

@@ -30,7 +30,7 @@ class CacheTest extends TestCase
 
     public function setUp(): void
     {
-        $this->root = $this->getUniqueTmpDirectory();
+        $this->root = self::getUniqueTmpDirectory();
         $this->files = array();
         $zeros = str_repeat('0', 1000);
 

tests/Composer/Test/Command/ConfigCommandTest.php

@@ -0,0 +1,146 @@
+<?php declare(strict_types=1);
+
+/*
+ * This file is part of Composer.
+ *
+ * (c) Nils Adermann <naderman@naderman.de>
+ *     Jordi Boggiano <j.boggiano@seld.be>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Composer\Test\Command;
+
+use Composer\Composer;
+use Composer\Config;
+use Composer\Script\Event as ScriptEvent;
+use Composer\Test\TestCase;
+use Composer\Util\Filesystem;
+
+class ConfigCommandTest extends TestCase
+{
+    /**
+     * @dataProvider provideConfigUpdates
+     * @param array<mixed> $before
+     * @param array<mixed> $command
+     * @param array<mixed> $expected
+     */
+    public function testConfigUpdates(array $before, array $command, array $expected): void
+    {
+        $this->initTempComposer($before);
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run(array_merge(['command' => 'config'], $command));
+
+        $appTester->assertCommandIsSuccessful($appTester->getDisplay());
+
+        $this->assertSame($expected, json_decode((string) file_get_contents('composer.json'), true));
+    }
+
+    public function provideConfigUpdates(): \Generator
+    {
+        yield 'set scripts' => [
+            [],
+            ['setting-key' => 'scripts.test', 'setting-value' => ['foo bar']],
+            ['scripts' => ['test' => 'foo bar']],
+        ];
+        yield 'unset scripts' => [
+            ['scripts' => ['test' => 'foo bar', 'lala' => 'baz']],
+            ['setting-key' => 'scripts.lala', '--unset' => true],
+            ['scripts' => ['test' => 'foo bar']],
+        ];
+        yield 'set single config with bool normalizer' => [
+            [],
+            ['setting-key' => 'use-github-api', 'setting-value' => ['1']],
+            ['config' => ['use-github-api' => true]],
+        ];
+        yield 'set multi config' => [
+            [],
+            ['setting-key' => 'github-protocols', 'setting-value' => ['https', 'git']],
+            ['config' => ['github-protocols' => ['https', 'git']]],
+        ];
+        yield 'set version' => [
+            [],
+            ['setting-key' => 'version', 'setting-value' => ['1.0.0']],
+            ['version' => '1.0.0'],
+        ];
+        yield 'unset version' => [
+            ['version' => '1.0.0'],
+            ['setting-key' => 'version', '--unset' => true],
+            [],
+        ];
+        yield 'unset arbitrary property' => [
+            ['random-prop' => '1.0.0'],
+            ['setting-key' => 'random-prop', '--unset' => true],
+            [],
+        ];
+        yield 'set preferred-install' => [
+            [],
+            ['setting-key' => 'preferred-install.foo/*', 'setting-value' => ['source']],
+            ['config' => ['preferred-install' => ['foo/*' => 'source']]],
+        ];
+        yield 'unset preferred-install' => [
+            ['config' => ['preferred-install' => ['foo/*' => 'source']]],
+            ['setting-key' => 'preferred-install.foo/*', '--unset' => true],
+            ['config' => ['preferred-install' => []]],
+        ];
+    }
+
+    /**
+     * @dataProvider provideConfigReads
+     * @param array<mixed> $composerJson
+     * @param array<mixed> $command
+     */
+    public function testConfigReads(array $composerJson, array $command, string $expected): void
+    {
+        $this->initTempComposer($composerJson);
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run(array_merge(['command' => 'config'], $command));
+
+        $appTester->assertCommandIsSuccessful();
+
+        $this->assertSame($expected, trim($appTester->getDisplay(true)));
+        $this->assertSame($composerJson, json_decode((string) file_get_contents('composer.json'), true), 'The composer.json should not be modified by config reads');
+    }
+
+    public function provideConfigReads(): \Generator
+    {
+        yield 'read description' => [
+            ['description' => 'foo bar'],
+            ['setting-key' => 'description'],
+            'foo bar',
+        ];
+        yield 'read vendor-dir with source' => [
+            ['config' => ['vendor-dir' => 'lala']],
+            ['setting-key' => 'vendor-dir', '--source' => true],
+            'lala (./composer.json)',
+        ];
+        yield 'read default vendor-dir' => [
+            [],
+            ['setting-key' => 'vendor-dir'],
+            'vendor',
+        ];
+        yield 'read repos by named key' => [
+            ['repositories' => ['foo' => ['type' => 'vcs', 'url' => 'https://example.org']]],
+            ['setting-key' => 'repositories.foo'],
+            '{"type":"vcs","url":"https://example.org"}',
+        ];
+        yield 'read repos by numeric index' => [
+            ['repositories' => [['type' => 'vcs', 'url' => 'https://example.org']]],
+            ['setting-key' => 'repos.0'],
+            '{"type":"vcs","url":"https://example.org"}',
+        ];
+        yield 'read all repos includes the default packagist' => [
+            ['repositories' => ['foo' => ['type' => 'vcs', 'url' => 'https://example.org']]],
+            ['setting-key' => 'repos'],
+            '{"foo":{"type":"vcs","url":"https://example.org"},"packagist.org":{"type":"composer","url":"https://repo.packagist.org"}}',
+        ];
+        yield 'read all repos does not include the disabled packagist' => [
+            ['repositories' => ['foo' => ['type' => 'vcs', 'url' => 'https://example.org'], 'packagist.org' => false]],
+            ['setting-key' => 'repos'],
+            '{"foo":{"type":"vcs","url":"https://example.org"}}',
+        ];
+    }
+}

tests/Composer/Test/Command/RunScriptCommandTest.php

@@ -12,35 +12,14 @@
 
 namespace Composer\Test\Command;
 
-use Composer\Command\RunScriptCommand;
 use Composer\Composer;
 use Composer\Config;
-use Composer\Console\Application;
 use Composer\Script\Event as ScriptEvent;
 use Composer\Test\TestCase;
 use Composer\Util\Filesystem;
-use Symfony\Component\Console\Tester\ApplicationTester;
 
 class RunScriptCommandTest extends TestCase
 {
-    /**
-     * @var string
-     */
-    private $home;
-
-    public function setUp(): void
-    {
-        $this->home = $this->getUniqueTmpDirectory();
-    }
-
-    protected function tearDown(): void
-    {
-        parent::tearDown();
-
-        $fs = new Filesystem();
-        $fs->removeDirectory($this->home);
-    }
-
     /**
      * @dataProvider getDevOptions
      * @param bool $dev
@@ -112,7 +91,7 @@ class RunScriptCommandTest extends TestCase
 
     public function testCanListScripts(): void
     {
-        $manifest = [
+        $this->initTempComposer([
             'scripts' => [
                 'test' => '@php test',
                 'fix-cs' => 'php-cs-fixer fix',
@@ -120,20 +99,14 @@ class RunScriptCommandTest extends TestCase
             'scripts-descriptions' => [
                 'fix-cs' => 'Run the codestyle fixer',
             ],
-        ];
+        ]);
 
-        file_put_contents($this->home.'/composer.json', json_encode($manifest));
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'run-script', '--list' => true]);
 
-        $application = new Application();
+        $appTester->assertCommandIsSuccessful();
-        $application->setAutoExit(false);
-        $application->add(new RunScriptCommand());
 
-        $tester = new ApplicationTester($application);
+        $output = $appTester->getDisplay();
-        $tester->run(['command' => 'run-script', '--list' => true, '-d' => $this->home]);
-
-        $tester->assertCommandIsSuccessful();
-
-        $output = $tester->getDisplay();
 
         $this->assertStringContainsString('Runs the test script as defined in composer.json.', $output, 'The default description for the test script should be printed');
         $this->assertStringContainsString('Run the codestyle fixer', $output, 'The custom description for the fix-cs script should be printed');

tests/Composer/Test/Config/JsonConfigSourceTest.php

@@ -37,7 +37,7 @@ class JsonConfigSourceTest extends TestCase
     protected function setUp(): void
     {
         $this->fs = new Filesystem;
-        $this->workingDir = $this->getUniqueTmpDirectory();
+        $this->workingDir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Downloader/FileDownloaderTest.php

@@ -69,7 +69,7 @@ class FileDownloaderTest extends TestCase
         $package = $this->getPackage();
         $package->setDistUrl('url');
 
-        $path = $this->createTempFile($this->getUniqueTmpDirectory());
+        $path = $this->createTempFile(self::getUniqueTmpDirectory());
         $downloader = $this->getDownloader();
 
         try {
@@ -105,7 +105,7 @@ class FileDownloaderTest extends TestCase
         $package = $this->getPackage();
         $package->setDistUrl('http://example.com/script.js');
 
-        $path = $this->getUniqueTmpDirectory();
+        $path = self::getUniqueTmpDirectory();
         $ioMock = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
         $ioMock->expects($this->any())
             ->method('write')
@@ -142,7 +142,7 @@ class FileDownloaderTest extends TestCase
 
     public function testDownloadWithCustomProcessedUrl(): void
     {
-        $path = $this->getUniqueTmpDirectory();
+        $path = self::getUniqueTmpDirectory();
 
         $package = $this->getPackage();
         $package->setDistUrl('url');
@@ -225,7 +225,7 @@ class FileDownloaderTest extends TestCase
 
     public function testDownloadWithCustomCacheKey(): void
     {
-        $path = $this->getUniqueTmpDirectory();
+        $path = self::getUniqueTmpDirectory();
 
         $package = $this->getPackage();
         $package->setDistUrl('url');
@@ -339,7 +339,7 @@ class FileDownloaderTest extends TestCase
 
         $filesystem = $this->getMockBuilder('Composer\Util\Filesystem')->getMock();
 
-        $path = $this->getUniqueTmpDirectory();
+        $path = self::getUniqueTmpDirectory();
         $config = $this->getConfig(['vendor-dir' => $path.'/vendor']);
 
         $downloader = $this->getDownloader(null, $config, null, null, null, $filesystem);
@@ -384,7 +384,7 @@ class FileDownloaderTest extends TestCase
                 [$this->stringContains('Downgrading')]
             );
 
-        $path = $this->getUniqueTmpDirectory();
+        $path = self::getUniqueTmpDirectory();
         $config = $this->getConfig(['vendor-dir' => $path.'/vendor']);
 
         $filesystem = $this->getMockBuilder('Composer\Util\Filesystem')->getMock();

tests/Composer/Test/Downloader/FossilDownloaderTest.php

@@ -23,7 +23,7 @@ class FossilDownloaderTest extends TestCase
 
     protected function setUp(): void
     {
-        $this->workingDir = $this->getUniqueTmpDirectory();
+        $this->workingDir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Downloader/GitDownloaderTest.php

@@ -33,7 +33,7 @@ class GitDownloaderTest extends TestCase
         $this->initGitVersion('1.0.0');
 
         $this->fs = new Filesystem;
-        $this->workingDir = $this->getUniqueTmpDirectory();
+        $this->workingDir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Downloader/HgDownloaderTest.php

@@ -23,7 +23,7 @@ class HgDownloaderTest extends TestCase
 
     protected function setUp(): void
     {
-        $this->workingDir = $this->getUniqueTmpDirectory();
+        $this->workingDir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Downloader/PerforceDownloaderTest.php

@@ -43,7 +43,7 @@ class PerforceDownloaderTest extends TestCase
 
     protected function setUp(): void
     {
-        $this->testPath = $this->getUniqueTmpDirectory();
+        $this->testPath = self::getUniqueTmpDirectory();
         $this->repoConfig = $this->getRepoConfig();
         $this->config = $this->getConfig();
         $this->io = $this->getMockIoInterface();

tests/Composer/Test/Downloader/XzDownloaderTest.php

@@ -36,7 +36,7 @@ class XzDownloaderTest extends TestCase
         if (Platform::isWindows()) {
             $this->markTestSkipped('Skip test on Windows');
         }
-        $this->testDir = $this->getUniqueTmpDirectory();
+        $this->testDir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Downloader/ZipDownloaderTest.php

@@ -37,7 +37,7 @@ class ZipDownloaderTest extends TestCase
 
     public function setUp(): void
     {
-        $this->testDir = $this->getUniqueTmpDirectory();
+        $this->testDir = self::getUniqueTmpDirectory();
         $this->io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
         $this->config = $this->getMockBuilder('Composer\Config')->getMock();
         $dlConfig = $this->getMockBuilder('Composer\Config')->getMock();

tests/Composer/Test/InstalledVersionsTest.php

@@ -46,7 +46,7 @@ class InstalledVersionsTest extends TestCase
 
     public function setUp(): void
     {
-        $this->root = $this->getUniqueTmpDirectory();
+        $this->root = self::getUniqueTmpDirectory();
 
         $dir = $this->root;
         InstalledVersions::reload(require __DIR__.'/Repository/Fixtures/installed.php');

tests/Composer/Test/Installer/BinaryInstallerTest.php

@@ -48,7 +48,7 @@ class BinaryInstallerTest extends TestCase
     {
         $this->fs = new Filesystem;
 
-        $this->rootDir = $this->getUniqueTmpDirectory();
+        $this->rootDir = self::getUniqueTmpDirectory();
         $this->vendorDir = $this->rootDir.DIRECTORY_SEPARATOR.'vendor';
         $this->ensureDirectoryExistsAndClear($this->vendorDir);
 

tests/Composer/Test/Installer/LibraryInstallerTest.php

@@ -74,7 +74,7 @@ class LibraryInstallerTest extends TestCase
         $this->config = new Config(false);
         $this->composer->setConfig($this->config);
 
-        $this->rootDir = $this->getUniqueTmpDirectory();
+        $this->rootDir = self::getUniqueTmpDirectory();
         $this->vendorDir = $this->rootDir.DIRECTORY_SEPARATOR.'vendor';
         self::ensureDirectoryExistsAndClear($this->vendorDir);
 

tests/Composer/Test/InstallerTest.php

@@ -45,7 +45,7 @@ use Symfony\Component\Console\Formatter\OutputFormatter;
 class InstallerTest extends TestCase
 {
     /** @var string */
-    protected $prevCwd;
+    private $prevCwd;
     /** @var ?string */
     protected $tempComposerHome;
 

tests/Composer/Test/Package/Archiver/ArchivableFilesFinderTest.php

@@ -39,7 +39,7 @@ class ArchivableFilesFinderTest extends TestCase
         $this->fs = $fs;
 
         $this->sources = $fs->normalizePath(
-            $this->getUniqueTmpDirectory()
+            self::getUniqueTmpDirectory()
         );
 
         $fileTree = array(

tests/Composer/Test/Package/Archiver/ArchiverTest.php

@@ -38,7 +38,7 @@ abstract class ArchiverTest extends TestCase
     {
         $this->filesystem = new Filesystem();
         $this->process = new ProcessExecutor();
-        $this->testDir = $this->getUniqueTmpDirectory();
+        $this->testDir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Package/Archiver/PharArchiverTest.php

@@ -22,7 +22,7 @@ class PharArchiverTest extends ArchiverTest
         // Set up repository
         $this->setupDummyRepo();
         $package = $this->setupPackage();
-        $target = $this->getUniqueTmpDirectory().'/composer_archiver_test.tar';
+        $target = self::getUniqueTmpDirectory().'/composer_archiver_test.tar';
 
         // Test archive
         $archiver = new PharArchiver();
@@ -37,7 +37,7 @@ class PharArchiverTest extends ArchiverTest
         // Set up repository
         $this->setupDummyRepo();
         $package = $this->setupPackage();
-        $target = $this->getUniqueTmpDirectory().'/composer_archiver_test.zip';
+        $target = self::getUniqueTmpDirectory().'/composer_archiver_test.zip';
 
         // Test archive
         $archiver = new PharArchiver();

tests/Composer/Test/Plugin/PluginInstallerTest.php

@@ -73,7 +73,7 @@ class PluginInstallerTest extends TestCase
     {
         $loader = new JsonLoader(new ArrayLoader());
         $this->packages = array();
-        $this->directory = $this->getUniqueTmpDirectory();
+        $this->directory = self::getUniqueTmpDirectory();
         for ($i = 1; $i <= 8; $i++) {
             $filename = '/Fixtures/plugin-v'.$i.'/composer.json';
             mkdir(dirname($this->directory . $filename), 0777, true);

tests/Composer/Test/Repository/FilesystemRepositoryTest.php

@@ -127,7 +127,7 @@ class FilesystemRepositoryTest extends TestCase
 
     public function testRepositoryWritesInstalledPhp(): void
     {
-        $dir = $this->getUniqueTmpDirectory();
+        $dir = self::getUniqueTmpDirectory();
         chdir($dir);
 
         $json = new JsonFile($dir.'/installed.json');

tests/Composer/Test/Repository/RepositoryManagerTest.php

@@ -24,7 +24,7 @@ class RepositoryManagerTest extends TestCase
 
     public function setUp(): void
     {
-        $this->tmpdir = $this->getUniqueTmpDirectory();
+        $this->tmpdir = self::getUniqueTmpDirectory();
     }
 
     protected function tearDown(): void

tests/Composer/Test/Repository/Vcs/FossilDriverTest.php

@@ -30,7 +30,7 @@ class FossilDriverTest extends TestCase
 
     public function setUp(): void
     {
-        $this->home = $this->getUniqueTmpDirectory();
+        $this->home = self::getUniqueTmpDirectory();
         $this->config = new Config();
         $this->config->merge(array(
             'config' => array(

tests/Composer/Test/Repository/Vcs/GitBitbucketDriverTest.php

@@ -37,7 +37,7 @@ class GitBitbucketDriverTest extends TestCase
     {
         $this->io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
 
-        $this->home = $this->getUniqueTmpDirectory();
+        $this->home = self::getUniqueTmpDirectory();
 
         $this->config = new Config();
         $this->config->merge(array(

tests/Composer/Test/Repository/Vcs/GitHubDriverTest.php

@@ -28,7 +28,7 @@ class GitHubDriverTest extends TestCase
 
     public function setUp(): void
     {
-        $this->home = $this->getUniqueTmpDirectory();
+        $this->home = self::getUniqueTmpDirectory();
         $this->config = new Config();
         $this->config->merge(array(
             'config' => array(

tests/Composer/Test/Repository/Vcs/GitLabDriverTest.php

@@ -51,7 +51,7 @@ class GitLabDriverTest extends TestCase
 
     public function setUp(): void
     {
-        $this->home = $this->getUniqueTmpDirectory();
+        $this->home = self::getUniqueTmpDirectory();
         $this->config = $this->getConfig([
             'home' => $this->home,
             'gitlab-domains' => array(

tests/Composer/Test/Repository/Vcs/HgDriverTest.php

@@ -30,7 +30,7 @@ class HgDriverTest extends TestCase
     public function setUp(): void
     {
         $this->io = $this->getMockBuilder('Composer\IO\IOInterface')->getMock();
-        $this->home = $this->getUniqueTmpDirectory();
+        $this->home = self::getUniqueTmpDirectory();
         $this->config = new Config();
         $this->config->merge(array(
             'config' => array(

tests/Composer/Test/Repository/Vcs/PerforceDriverTest.php

@@ -63,7 +63,7 @@ class PerforceDriverTest extends TestCase
 
     protected function setUp(): void
     {
-        $this->testPath = $this->getUniqueTmpDirectory();
+        $this->testPath = self::getUniqueTmpDirectory();
         $this->config = $this->getTestConfig($this->testPath);
         $this->repoConfig = array(
             'url' => self::TEST_URL,

tests/Composer/Test/Repository/Vcs/SvnDriverTest.php

@@ -31,7 +31,7 @@ class SvnDriverTest extends TestCase
 
     public function setUp(): void
     {
-        $this->home = $this->getUniqueTmpDirectory();
+        $this->home = self::getUniqueTmpDirectory();
         $this->config = new Config();
         $this->config->merge(array(
             'config' => array(

tests/Composer/Test/Repository/VcsRepositoryTest.php

@@ -53,8 +53,8 @@ class VcsRepositoryTest extends TestCase
         }
 
         $oldCwd = Platform::getCwd();
-        self::$composerHome = $this->getUniqueTmpDirectory();
+        self::$composerHome = self::getUniqueTmpDirectory();
-        self::$gitRepo = $this->getUniqueTmpDirectory();
+        self::$gitRepo = self::getUniqueTmpDirectory();
 
         if (!@chdir(self::$gitRepo)) {
             $this->skipped = 'Could not move into the temp git repo '.self::$gitRepo;

tests/Composer/Test/TestCase.php

@@ -13,7 +13,9 @@
 namespace Composer\Test;
 
 use Composer\Config;
+use Composer\Console\Application;
 use Composer\IO\IOInterface;
+use Composer\Json\JsonFile;
 use Composer\Pcre\Preg;
 use Composer\Semver\VersionParser;
 use Composer\Package\PackageInterface;
@@ -23,6 +25,7 @@ use Composer\Test\Mock\ProcessExecutorMock;
 use Composer\Util\Filesystem;
 use Composer\Util\Platform;
 use Composer\Util\Silencer;
+use Symfony\Component\Console\Tester\ApplicationTester;
 use Symfony\Component\Process\ExecutableFinder;
 use Composer\Package\Loader\ArrayLoader;
 use Composer\Package\BasePackage;
@@ -53,6 +56,12 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase
      * @var list<ProcessExecutorMock>
      */
     private $processExecutorMocks = [];
+    /**
+     * @var list<string>
+     */
+    private $tempComposerDirs = [];
+    /** @var string|null */
+    private $prevCwd = null;
 
     protected function tearDown(): void
     {
@@ -63,6 +72,17 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase
         foreach ($this->processExecutorMocks as $mock) {
             $mock->assertComplete();
         }
+
+        if (null !== $this->prevCwd) {
+            chdir($this->prevCwd);
+            $this->prevCwd = null;
+            Platform::clearEnv('COMPOSER_HOME');
+            Platform::clearEnv('COMPOSER_DISABLE_XDEBUG_WARN');
+        }
+        $fs = new Filesystem();
+        foreach ($this->tempComposerDirs as $dir) {
+            $fs->removeDirectory($dir);
+        }
     }
 
     /**
@@ -84,6 +104,42 @@ abstract class TestCase extends \PHPUnit\Framework\TestCase
         throw new \RuntimeException('Failed to create a unique temporary directory.');
     }
 
+    /**
+     * Creates a composer.json / auth.json inside a temp dir and chdir() into it
+     *
+     * The directory will be cleaned up on tearDown automatically.
+     *
+     * @param mixed[] $composerJson
+     * @param mixed[] $authJson
+     * @return string the newly created temp dir
+     */
+    public function initTempComposer(array $composerJson = [], array $authJson = []): string
+    {
+        $dir = self::getUniqueTmpDirectory();
+
+        $this->tempComposerDirs[] = $dir;
+
+        $this->prevCwd = Platform::getCwd();
+
+        Platform::putEnv('COMPOSER_HOME', $dir.'/composer-home');
+        Platform::putEnv('COMPOSER_DISABLE_XDEBUG_WARN', '1');
+
+        chdir($dir);
+        file_put_contents($dir.'/composer.json', JsonFile::encode($composerJson, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE | JSON_FORCE_OBJECT));
+        file_put_contents($dir.'/auth.json', JsonFile::encode($authJson, JSON_UNESCAPED_SLASHES | JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE | JSON_FORCE_OBJECT));
+
+        return $dir;
+    }
+
+    public function getApplicationTester(): ApplicationTester
+    {
+        $application = new Application();
+        $application->setAutoExit(false);
+        $application->setCatchExceptions(false);
+
+        return new ApplicationTester($application);
+    }
+
     /**
      * @return VersionParser
      */

tests/Composer/Test/Util/FilesystemTest.php

@@ -35,8 +35,8 @@ class FilesystemTest extends TestCase
     public function setUp(): void
     {
         $this->fs = new Filesystem;
-        $this->workingDir = $this->getUniqueTmpDirectory();
+        $this->workingDir = self::getUniqueTmpDirectory();
-        $this->testFile = $this->getUniqueTmpDirectory() . '/composer_test_file';
+        $this->testFile = self::getUniqueTmpDirectory() . '/composer_test_file';
     }
 
     protected function tearDown(): void

tests/bootstrap.php

@@ -23,3 +23,8 @@ require __DIR__.'/../src/Composer/InstalledVersions.php';
 require __DIR__.'/Composer/Test/TestCase.php';
 
 Platform::putEnv('COMPOSER_TESTS_ARE_RUNNING', '1');
+
+// symfony/phpunit-bridge sets some default env vars which we do not need polluting the test env
+Platform::clearEnv('COMPOSER');
+Platform::clearEnv('COMPOSER_VENDOR_DIR');
+Platform::clearEnv('COMPOSER_BIN_DIR');