def test_212F_is_100C():
    assert convert(212, 'f', 'c') == 100
def test_upper_to_lower_works():
    assert convert(212, 'F', 'c') == 100
    assert convert(212, 'F', 'C') == 100
def test_0C_is_32F():
    assert convert(0, 'c', 'f') == 32
def test_neg_k_still_works():
    assert convert(-273.15, 'k', 'c') == 0
    assert convert(-0, 'k', 'c') == -273.15
def test_C_to_K():
    assert convert(0, 'c', 'k') == 273.15
def test_K_to_C():
    assert convert(0, 'k', 'c') == -273.15
def test_F_to_K():
    assert convert(-459.67, 'f', 'k') == 0
def test_K_to_F():
    assert convert(283.15, 'k', 'f') == 50