[8.x] Update the ParallelRunner to allow for a custom Runner to be resolved (#38374)

* Updates the `ParallelRunner` to allow for a custom `Runner` to be resolved instead of the default in Collision.

* Update src/Illuminate/Testing/ParallelRunner.php

Co-authored-by: Nuno Maduro <[email protected]>

* Update src/Illuminate/Testing/ParallelRunner.php

Co-authored-by: Nuno Maduro <[email protected]>

Co-authored-by: Nuno Maduro <[email protected]>

Author: lukeraymonddowning

src/Illuminate/Testing/ParallelRunner.php

@@ -21,6 +21,13 @@ class ParallelRunner implements RunnerInterface
      */
     protected static $applicationResolver;
 
+    /**
+     * The runner resolver callback.
+     *
+     * @var \Closure|null
+     */
+    protected static $runnerResolver;
+
     /**
      * The original test runner options.
      *
@@ -57,7 +64,11 @@ public function __construct(Options $options, OutputInterface $output)
             $output = new ParallelConsoleOutput($output);
         }
 
-        $this->runner = new WrapperRunner($options, $output);
+        $runnerResolver = static::$runnerResolver ?: function (Options $options, OutputInterface $output) {
+            return new WrapperRunner($options, $output);
+        };
+
+        $this->runner = call_user_func($runnerResolver, $options, $output);
     }
 
     /**
@@ -71,6 +82,17 @@ public static function resolveApplicationUsing($resolver)
         static::$applicationResolver = $resolver;
     }
 
+    /**
+     * Set the runner resolver callback.
+     *
+     * @param  \Closure|null  $resolver
+     * @return void
+     */
+    public static function resolveRunnerUsing($resolver)
+    {
+        static::$runnerResolver = $resolver;
+    }
+
     /**
      * Runs the test suite.
      *