chore: add GUT test framework

addons/gut/test/output_tests/test_one_of_everything.gd

@@ -0,0 +1,62 @@
+extends GutTest
+
+
+func test_failing():
+	assert_false(true)
+
+func test_passing():
+	assert_true(true)
+
+func test_pending():
+	pending('This is pending')
+
+func test_risky_no_assert():
+	var _a = 'b'
+	pass
+
+func test_push_error():
+	push_error('test error')
+	assert_true(true)
+	
+func test_expected_push_error():
+	push_error('test error')
+	assert_push_error('test error')
+
+func test_gut_warning():
+	gut.get_logger().warn('test warning')
+	assert_eq(1, 1)
+	
+func test_gut_error():
+	gut.get_logger().error("test gut error")
+	assert_between(2, 1, 3)
+
+func test_makes_an_orphan():
+	var _n = GutTest.new()
+	pass_test('passing')
+
+func test_makes_an_orphan_with_assert():
+	var _n = Node.new()
+	assert_no_new_orphans()
+
+
+class TestSkipThisScript:
+	extends GutTest
+	
+	func should_skip_script():
+		return "Skipping for demo purposes"
+		
+	func test_nothing():
+		pass_test('nothing')
+
+
+class TestInnerTestClass:
+	extends GutTest
+	
+	func test_failing():
+		assert_false(true)
+
+	func test_passing():
+		assert_true(true)
+
+	func test_pending():
+		pending('This is pending')