Added happy and sad tests for resolving a requested package and version

.gitignore

@@ -1,4 +1,5 @@
 /vendor/
 /psalm.xml
 /.phpunit.cache/
+/.phpunit.result.cache
 /.phpcs-cache

composer.json

@@ -26,7 +26,9 @@
     ],
     "require": {
         "php": "8.1.*||8.2.*||8.3.*",
-        "symfony/console": "^6.4"
+        "composer/composer": "^2.7",
+        "symfony/console": "^6.4",
+        "webmozart/assert": "^1.11"
     },
     "require-dev": {
         "doctrine/coding-standard": "^12.0",

test/unit/Command/DownloadCommandTest.php

@@ -8,21 +8,52 @@ use Php\Pie\Command\DownloadCommand;
 use PHPUnit\Framework\Attributes\CoversClass;
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Console\Input\InputInterface;
-use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Output\BufferedOutput;
+use Throwable;
+
+use const PHP_VERSION;
+use const PHP_VERSION_ID;
 
 #[CoversClass(DownloadCommand::class)]
 class DownloadCommandTest extends TestCase
 {
     public function testDownloadCommand(): void
     {
-        $input  = $this->createMock(InputInterface::class);
-        $output = $this->createMock(OutputInterface::class);
+        $input = $this->createMock(InputInterface::class);
+        $input->expects(self::once())
+            ->method('getArgument')
+            ->with('requested-package-and-version')
+            ->willReturn('ramsey/uuid');
 
-        $output->expects(self::once())
-            ->method('writeln')
-            ->with('<info>to do</info>');
+        $output = new BufferedOutput();
 
         $command = new DownloadCommand();
         self::assertSame(0, $command->execute($input, $output));
+
+        $outputString = $output->fetch();
+        self::assertStringContainsString('Found package: ramsey/uuid (version: ', $outputString);
+        self::assertStringContainsString('Dist download URL: https://api.github.com/repos/ramsey/uuid/zipball/', $outputString);
+    }
+
+    public function testDownloadCommandFailsWhenUsingIncompatiblePhpVersion(): void
+    {
+        if (PHP_VERSION_ID >= 80200) {
+            self::markTestSkipped('This test can only run on older than PHP 8.2 - you are running ' . PHP_VERSION);
+        }
+
+        $input = $this->createMock(InputInterface::class);
+        $input->expects(self::once())
+            ->method('getArgument')
+            ->with('requested-package-and-version')
+            ->willReturn('phpunit/phpunit:^11.0');
+
+        $output = new BufferedOutput();
+
+        $command = new DownloadCommand();
+
+        // @todo narrow this down to our true expected failure;
+        //       i.e. phpunit/phpunit:^11.0 should NOT be installable on PHP 8.1
+        $this->expectException(Throwable::class);
+        $command->execute($input, $output);
     }
 }