def METHOD_NAME(self):
    VECTORS = [
        (123456, 3, "123.456"),
        (4242, 7, "0.0004242"),
        (-123456, 3, "-123.456"),
        (-4242, 7, "-0.0004242"),
        (123, 5, "0.00123"),
        (100, 5, "0.001"),
        (123456789, 0, "123,456,789"),
        (100000000, 5, "1,000"),
        (100000001, 5, "1,000.00001"),
        (100001000, 5, "1,000.01"),
        (-100001000, 5, "-1,000.01"),
        (123_456_789_123_456_789_123_456_789, 18, "123,456,789.123456789123456789"),
    ]
    for v in VECTORS:
        self.assertEqual(strings.format_amount(v[0], v[1]), v[2])