def test_solution11():
assert solution(1989) == 'MCMLXXXIX'
def test_solution2():
assert solution(4) == 'IV'
def test_solution9():
assert solution(1000) == 'M'
def test_solution10():
assert solution(1889) == 'MDCCCLXXXIX'
def test_solution1():
assert solution(1) == 'I'
def test_solution8():
assert solution(984) == 'CMLXXXIV'
def test_solution7():
assert solution(91) == 'XCI'
def test_solution6():
assert solution(89) == 'LXXXIX'
def test_solution5():
assert solution(21) == 'XXI'
def test_solution4():
assert solution(14) == 'XIV'
def test_solution3():
assert solution(6) == 'VI'
