test: Add check to ensure the right version of Composer is used

tests/ComposerVersionProvider.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Bamarni\Composer\Bin\Tests;
+
+use Symfony\Component\Process\Process;
+use function preg_match;
+
+final class ComposerVersionProvider
+{
+    public static function getComposerVersion(): string
+    {
+        $composerVersionProcess = Process::fromShellCommandline(
+            'composer --version --no-ansi --no-interaction',
+            null,
+            null,
+            null,
+            1
+        );
+
+        $composerVersionProcess->mustRun();
+
+        $output = $composerVersionProcess->getOutput();
+
+        return self::extractComposerVersion($output);
+    }
+
+    private static function extractComposerVersion(string $versionOutput): string
+    {
+        preg_match('/Composer version (?<version>\d+\.\d+\.\d+) /', $versionOutput, $matches);
+
+        return $matches['version'];
+    }
+}

tests/ComposerVersionProviderTest.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Bamarni\Composer\Bin\Tests;
+
+use PHPUnit\Framework\TestCase;
+use function preg_match;
+use function sprintf;
+
+/**
+ * @group e2e
+ * @covers \Bamarni\Composer\Bin\Tests\ComposerVersionProvider
+ */
+final class ComposerVersionProviderTest extends TestCase
+{
+    public function test_it_can_get_the_composer_version(): void
+    {
+        $expectedPattern = '/^\d+\.\d+\.\d+$/';
+
+        $actual = ComposerVersionProvider::getComposerVersion();
+
+        self::assertSame(
+            1,
+            preg_match($expectedPattern, $actual),
+            sprintf(
+                'The version "%s" does not match the pattern "%s".',
+                $actual,
+                $expectedPattern
+            )
+        );
+    }
+}

tests/EndToEndTest.php

@@ -4,10 +4,10 @@
 
 namespace Bamarni\Composer\Bin\Tests;
 
+use Composer\Semver\Semver;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\Process\Process;
-
 use function array_map;
 use function basename;
 use function dirname;
@@ -21,7 +21,6 @@
 use function sprintf;
 use function str_replace;
 use function trim;
-
 use const PHP_EOL;
 
 /**
@@ -32,6 +31,17 @@ final class EndToEndTest extends TestCase
 {
     private const E2E_DIR = __DIR__.'/../e2e';
 
+    private const COMPOSER_VERSION_CONSTRAINT = '^2.8.2';
+
+    public function test_it_has_the_required_composer_version(): void
+    {
+        $composerVersion = ComposerVersionProvider::getComposerVersion();
+
+        self::assertTrue(
+            Semver::satisfies($composerVersion, self::COMPOSER_VERSION_CONSTRAINT)
+        );
+    }
+
     /**
      * @dataProvider scenarioProvider
      */