Make it easier to mock the required checks for unit testing

Author: AydinHassan

src/ExerciseRunner/CgiRunner.php

@@ -50,6 +50,15 @@ class CgiRunner implements ExerciseRunnerInterface
      */
     private $requestRenderer;
 
+    /**
+     * @var array
+     */
+    private static $requiredChecks = [
+        FileExistsCheck::class,
+        PhpLintCheck::class,
+        CodeParseCheck::class,
+    ];
+
     /**
      * Requires the exercise instance and an event dispatcher. This runner requires the `php-cgi` binary to
      * be available. It will check for it's existence in the system's $PATH variable or the same
@@ -106,11 +115,7 @@ public function getName()
      */
     public function getRequiredChecks()
     {
-        return [
-            FileExistsCheck::class,
-            PhpLintCheck::class,
-            CodeParseCheck::class,
-        ];
+        return static::$requiredChecks;
     }
 
     /**

src/ExerciseRunner/CliRunner.php

@@ -44,6 +44,15 @@ class CliRunner implements ExerciseRunnerInterface
      */
     private $eventDispatcher;
 
+    /**
+     * @var array
+     */
+    private static $requiredChecks = [
+        FileExistsCheck::class,
+        PhpLintCheck::class,
+        CodeParseCheck::class,
+    ];
+
     /**
      * Requires the exercise instance and an event dispatcher.
      *
@@ -71,11 +80,7 @@ public function getName()
      */
     public function getRequiredChecks()
     {
-        return [
-            FileExistsCheck::class,
-            PhpLintCheck::class,
-            CodeParseCheck::class,
-        ];
+        return static::$requiredChecks;
     }
 
     /**