def calculate_kinetic_energy(mass, velocity): 
    """Returns kinetic energy of mass [kg] with velocity [ms]."""
    return 0.5 * mass * velocity ** 2

    def test_calculate_kinetic_energy():
        mass = 10 # [kg]
    velocity = 4 # [m/s]
    assert calculate_kinetic_energy(mass, velocity) == 80