Add test for used symbol collection use case

Signed-off-by: Andreas Frömer <andreas.froemer@check24.de>

tests/Unit/UseCase/CollectUsedSymbolsUseCaseTest.php

@@ -0,0 +1,69 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Icanhazstring\Composer\Test\Unused\Unit\UseCase;
+
+use Composer\Composer;
+use Composer\Config;
+use Composer\Package\PackageInterface;
+use Generator;
+use Icanhazstring\Composer\Unused\Symbol\Loader\SymbolLoaderInterface;
+use Icanhazstring\Composer\Unused\Symbol\Symbol;
+use Icanhazstring\Composer\Unused\Symbol\SymbolInterface;
+use Icanhazstring\Composer\Unused\UseCase\CollectUsedSymbolsUseCase;
+use PHPUnit\Framework\TestCase;
+use Prophecy\Argument;
+use Prophecy\PhpUnit\ProphecyTrait;
+use function iterator_to_array;
+
+class CollectUsedSymbolsUseCaseTest extends TestCase
+{
+    use ProphecyTrait;
+
+    /**
+     * @param array<mixed> $values
+     * @return Generator<mixed>
+     */
+    private function arrayAsGenerator(array $values): Generator
+    {
+        yield from $values;
+    }
+
+    /**
+     * @test
+     */
+    public function itRemoveRootNamespaceSymbols(): void
+    {
+        $rootPackage = $this->prophesize(PackageInterface::class);
+        $rootPackage->getAutoload()->willReturn(['psr-4' => ['Test\\' => 'src']]);
+
+        $configSource = $this->prophesize(Config\ConfigSourceInterface::class);
+        $configSource->getName()->willReturn(__DIR__);
+
+        $composerConfig = $this->prophesize(Config::class);
+        $composerConfig->getConfigSource()->willReturn($configSource->reveal());
+
+        $composer = $this->prophesize(Composer::class);
+        $composer->getPackage()->willReturn($rootPackage);
+        $composer->getConfig()->willReturn($composerConfig->reveal());
+
+        $symbolLoader = $this->prophesize(SymbolLoaderInterface::class);
+        $symbolLoader->load(Argument::any())->willReturn(
+            $this->arrayAsGenerator([
+                new Symbol('Test\\Sub\\Classname'),
+                new Symbol('Test\\SecondClassname'),
+                new Symbol('ShouldStay\\Classname')
+            ])
+        );
+
+        $useCase = new CollectUsedSymbolsUseCase($symbolLoader->reveal());
+        /** @var array<SymbolInterface> $symbols */
+        $symbols = iterator_to_array($useCase->execute($composer->reveal()));
+
+        $symbol = current($symbols);
+
+        self::assertCount(1, $symbols);
+        self::assertSame('ShouldStay\\Classname', $symbol->getIdentifier());
+    }
+}