tests: skip test if mixin markers are already present in model

We're also testing Laravel 5.5 which contains them (they were removed later)

tests/Console/EloquentCommandTest.php

@@ -14,12 +14,11 @@ class EloquentCommandTest extends TestCase
     public function testCommand()
     {
         $modelFilename = $this->getVendorModelFilename();
-
-        // Ensure the mixins are not present
         $modelSource = file_get_contents($modelFilename);
-        $this->assertStringNotContainsString('* @mixin \\Eloquent', $modelSource);
-        $this->assertStringNotContainsString('* @mixin \\Illuminate\\Database\\Eloquent\\Builder', $modelSource);
-        $this->assertStringNotContainsString('* @mixin \\Illuminate\\Database\\Query\\Builder', $modelSource);
+        if (false !== strpos($modelSource, '* @mixin')) {
+            $msg = sprintf('Class %s already contains the @mixin markers', Model::class);
+            $this->markTestSkipped($msg);
+        }
 
         $actualContent = null;
         $mockFilesystem = Mockery::mock(Filesystem::class);

tests/TestCase.php

@@ -4,7 +4,6 @@
 
 use Illuminate\Console\Command;
 use Orchestra\Testbench\TestCase as BaseTestCase;
-use PHPUnit\Framework\Assert;
 use Symfony\Component\Console\Tester\CommandTester;
 
 abstract class TestCase extends BaseTestCase
@@ -34,21 +33,4 @@ protected function runCommand(Command $command, array $arguments = [], array $in
 
         return $tester;
     }
-
-    /**
-     * @todo if support for Laravel 5.5 is dropped, this shim can be replaced with actual parent call
-     *
-     * @param string $needle
-     * @param string $haystack
-     * @param string $message
-     */
-    public static function assertStringNotContainsString(string $needle, string $haystack, string $message = ''): void
-    {
-        if (!method_exists(Assert::class, 'assertStringContainsString')) {
-            parent::assertNotContains($needle, $haystack, $message);
-            return;
-        }
-
-        parent::assertStringNotContainsString($needle, $haystack, $message);
-    }
 }