def test_inches_less_than_cm(value):
"""A given length is less measured in inches than in cm."""
assume(value > 0)
converted = convert_units(value, 'inches', 'cm')
assert value < converted
def test_cm_less_than_mm(value):
"""A given length is less measured in cm than in mm."""
assume(value > 0)
converted = convert_units(value, 'cm', 'mm')
assert value < converted
def test_cm_greater_than_inches(value):
"""A given length is greater measured in cm than in inches."""
assume(value > 0)
converted = convert_units(value, 'cm', 'inches')
assert value > converted
def test_mm_greater_than_cm(value):
"""A given length is greater measured in mm than in cm."""
assume(value > 0)
converted = convert_units(value, 'mm', 'cm')
assert value > converted
def test_roundtrip(value, source_units, target_units):
"""Round-trip conversion should not change the value."""
converted = convert_units(value, source_units, target_units)
round_tripped = convert_units(converted, target_units, source_units)
assert almost_equal(round_tripped, value)
def test_identity(value, units):
"""Converting to the same unit is the identity."""
converted = convert_units(value, units, units)
assert converted == value