Add standalone testmode support (#219)

* Add standalone support.

* Add standalone tests.

* UnityStandaloneScripts volume on windows

* Update test framework in test project.

* Revert IL2CPP setting in test project.
Add test for IL2CPP.

* Update dist/test-standalone-scripts/Assets/Player/UnityTestRunnerAction/TestRunCallback.cs

Co-authored-by: Webber Takken <webber.nl@gmail.com>

* Use 2019.2.21f1

* Unity is being dumb, use 2019.4.40f1 for all workflows.

* Disable PlayerConnection on build.
Print player log.

* Add comment about code coverage support in standalone.

* Update node-version in test

---------

Co-authored-by: Webber Takken <webber.nl@gmail.com>

dist/test-standalone-scripts/Assets/Editor/UnityTestRunnerAction/PlayerBuildModifier.cs

@@ -0,0 +1,49 @@
+using System;
+using System.Linq;
+using UnityEditor;
+using UnityEditor.TestTools;
+using UnityEngine;
+using UnityEngine.TestTools;
+using UnityTestRunnerAction;
+
+[assembly: TestPlayerBuildModifier(typeof(HeadlessPlayModeSetup))]
+[assembly: PostBuildCleanup(typeof(HeadlessPlayModeSetup))]
+
+namespace UnityTestRunnerAction
+{
+    public class HeadlessPlayModeSetup : ITestPlayerBuildModifier, IPostBuildCleanup
+    {
+        private static bool s_RunningPlayerTests;
+        public BuildPlayerOptions ModifyOptions(BuildPlayerOptions playerOptions)
+        {
+            // Do not launch the player after the build completes. Disable the PlayerConnection.
+            playerOptions.options &= ~(BuildOptions.AutoRunPlayer | BuildOptions.ConnectToHost | BuildOptions.WaitForPlayerConnection);
+
+            // Not supporting Mac currently.
+            playerOptions.target = SystemInfo.operatingSystemFamily == OperatingSystemFamily.Windows ? BuildTarget.StandaloneWindows64 : BuildTarget.StandaloneLinux64;
+
+            string[] commandLineArgs = Environment.GetCommandLineArgs();
+            playerOptions.locationPathName = commandLineArgs[Array.IndexOf(commandLineArgs, "-builtTestRunnerPath") + 1]; ;
+
+            // Instruct the cleanup to exit the Editor if the run came from the command line. 
+            // The variable is static because the cleanup is being invoked in a new instance of the class.
+            s_RunningPlayerTests = true;
+            return playerOptions;
+        }
+
+        public void Cleanup()
+        {
+            if (s_RunningPlayerTests && IsRunningTestsFromCommandLine())
+            {
+                // Exit the Editor on the next update, allowing for other PostBuildCleanup steps to run.
+                EditorApplication.update += () => { EditorApplication.Exit(0); };
+            }
+        }
+
+        private static bool IsRunningTestsFromCommandLine()
+        {
+            var commandLineArgs = Environment.GetCommandLineArgs();
+            return commandLineArgs.Any(value => value == "-runTests");
+        }
+    }
+}