Added tests for mouse.set_pos()

[Graphcalibur]

Addresses #1764.

[MyreMylar]

Thank you for the contribution!

Looks like set_pos is a bit tricky. Perhaps try something like this?

import pygame

pygame.display.init()

# window has to be one pixel larger than mouse positions
window = pygame.display.set_mode((1000, 1000))

expected_pos = ((1, 1), (1, 400), (912, 566), (999, 999), (999, 0), (0, 999))
for x, y in expected_pos:
    pygame.event.get()  # clear all startup events off the event queue

    pygame.mouse.set_pos(x, y)
    ready_to_test = False
    while not ready_to_test:
        # need to process the event queue to move the mouse
        for event in pygame.event.get():
            if event.type == pygame.MOUSEMOTION:
                ready_to_test = True

    pygame.display.update()
    found_pos = pygame.mouse.get_pos()
    self.assertTrue(found_pos, (x, y))

[Graphcalibur]

Thank you for the help! I think this commit should get it to work properly.

[MyreMylar]

All looks good 👍 🎉