def test_4_gives_IV(): assert_equals(to_roman_numeral(4), "IV")
def test_999_gives_CMXCIX(): assert_equals(to_roman_numeral(999), "CMXCIX")
def test_18_gives_XVIII(): assert_equals(to_roman_numeral(18), "XVIII")
def test_1438_gives_MCDXXXVIII(): assert_equals(to_roman_numeral(1438), "MCDXXXVIII")
def test_1_gives_I(): assert_equals(to_roman_numeral(1), "I")
def test_1000_gives_M(): assert_equals(to_roman_numeral(1000), "M")
def test_500_gives_D(): assert_equals(to_roman_numeral(500), "D")
def test_50_gives_L(): assert_equals(to_roman_numeral(50), "L")
def test_10_gives_X(): assert_equals(to_roman_numeral(10), "X")
def test_5_gives_V(): assert_equals(to_roman_numeral(5), "V")