def test_start_with_minus():
string = {'exp': '-2 + 2 = 0'}
assert transformation(
'{exp}'.format(**string)) == 'minus two plus two equals zero'
def test_one_long_function():
string = {'exp': '-8 + 6 / 2 * 2 = -2'}
assert transformation(
'{exp}'.format(**string)
) == 'minus eight plus six divide two multiply two equals minus two'
def test_task_example():
string = {'exp': '3 + 7 = 10'}
assert transformation(
'{exp}'.format(**string)) == 'three plus seven equals ten'
def test_has_alpha():
string = {'exp': '3 * a = 9'}
assert transformation('{exp}'.format(**string)) == 'invalid input.'
def test_invalid_function():
string = {'exp': '3 ** 3 = 9'}
assert transformation('{exp}'.format(**string)) == 'invalid input.'
def test_random_space():
string = {'exp': ' 3+ 7= 10 '}
assert transformation(
'{exp}'.format(**string)) == 'three plus seven equals ten'