chore: add GUT test framework

addons/gut/test/samples/test_sample_all_passed.gd

@@ -0,0 +1,13 @@
+#A sample script for illustrating multiple scripts and what it looks like
+#when all tests pass.
+extends GutTest
+
+func test_works():
+	assert_true(true, 'This is true')
+
+func test_two():
+	assert_eq("two", "two", "This is also true")
+
+func test_3():
+	assert_ne("one", "two", "This is yet again true")
+