chore: add GUT test framework

addons/gut/test/unit/test_run_externally.gd

@@ -0,0 +1,18 @@
+extends GutInternalTester
+
+
+func test_can_make_one():
+	var inst = autofree(GutUtils.RunExternallyScene.instantiate())
+	assert_not_null(inst)
+
+
+func test_can_get_godot_help():
+	var inst = add_child_autofree(GutUtils.RunExternallyScene.instantiate())
+	var help_text = await inst.get_godot_help()
+	assert_string_contains(help_text, "-h, --help")
+
+
+func test_can_get_gut_help():
+	var inst = add_child_autofree(GutUtils.RunExternallyScene.instantiate())
+	var help_text = await inst.get_gut_help()
+	assert_string_contains(help_text, "The default behavior for GUT is to load")