Missing unit tests in `arcade.math`

[DragonMoffon]

Most of the methods in arcade.math are missing unit tests.

I also suspect many other functions in arcade are missing unit tests.

arcade.math function tests:

• clamp
• lerp
• lerp_2d
• lerp_3d
• lerp_angle
• rand_in_rect
• rand_in_circle
• rand_on_circle
• rand_on_line
• rand_angle_360_deg
• rand_angle_spread_deg
• rand_vec_spread_deg
• rand_vec_magnitude
• get_distance
• rotate_point
• get_angle_degrees
• get_angle_radians
• quaternion_rotation

[DragonMoffon]

Nearly every method has a test_function, but they are just smoke tests and do not test functionality.

[Pteris-211]

Hi, I'd like to work on it over the next few weeks. I'm new to the open source world, so if there's anything I need to pay particular attention to, please let me know.