chore: add GUT test framework

addons/gut/test/samples/test_singleton_examples.gd

@@ -0,0 +1,77 @@
+extends GutTest
+
+class UsesTime:
+	# Must have a reference to Engine Singleton that we can
+	# inject our double into.
+	var time := Time
+
+	var _start_time = -1
+	func start():
+		_start_time = time.get_ticks_msec()
+
+	func end():
+		var monday_extra = 0
+		if(time.get_date_dict_from_system().weekday == time.WEEKDAY_MONDAY):
+			monday_extra = 10
+		return time.get_ticks_msec() - _start_time + monday_extra
+
+
+# Fun fact, this test will fail if ran on any Monday.  I wrote this on a
+# Wednesday, so it passes.  This is a doozy of a flakey test.
+func test_calling_end_returns_elapsed_time_using_msecs():
+	var dbl_time = partial_double_singleton(Time).new()
+	var inst = UsesTime.new()
+	inst.time = dbl_time
+
+	stub(dbl_time.get_ticks_msec).to_return(0)
+	inst.start()
+	stub(dbl_time.get_ticks_msec).to_return(10)
+	assert_eq(inst.end(), 10)
+
+
+# Illustrate that enums are included in singleton doubles.
+func test_on_mondays_elapsed_time_is_longer_because_time_moves_slower_on_mondays():
+	var dbl_time = double_singleton(Time).new()
+	var inst = UsesTime.new()
+
+	inst.time = dbl_time
+	stub(dbl_time.get_date_dict_from_system)\
+		.to_return({
+			"year": 2025,
+			"month": 1,
+			"day": 1,
+			"weekday": Time.WEEKDAY_MONDAY})
+
+	stub(dbl_time.get_ticks_msec).to_return(0)
+	inst.start()
+	stub(dbl_time.get_ticks_msec).to_return(10)
+	assert_eq(inst.end(), 20)
+
+
+class UsesInput:
+	extends Node
+	var input := Input
+	var times_jumped = 0
+
+	func _physics_process(_delta):
+		# print(_delta, '  ', input.is_action_just_pressed("jump"))
+		if(input.is_action_just_pressed("jump")):
+			times_jumped += 1
+
+
+func test_jump_count_increased():
+	# gut.get_doubler().print_source = true
+	var dbl_input = double_singleton(Input).new()
+	var inst = add_child_autofree(UsesInput.new())
+	inst.input = dbl_input
+
+	stub(dbl_input.is_action_just_pressed.bind(&"jump", false))\
+		.to_return(true)
+		# .when_passed("jump", false)
+
+	await wait_physics_frames(1)
+	assert_eq(inst.times_jumped, 1)
+	assert_called(dbl_input.is_action_just_pressed.bind("jump", false))
+	assert_not_called(dbl_input.is_action_just_pressed.bind("jump", null))
+	print(gut.get_stubber().to_s())
+	# print(gut.get_spy().get_call_list_as_string(dbl_input))