FileSizeFormat format = new FileSizeFormat();
        if (unit == null) {
            assertEquals(expected, format.format(input));
        } else {
            assertEquals(expected, format.format(input, unit));
        }
    }

    @Test
    void testNegativeProgressedSize() {
        FileSizeFormat format = new FileSizeFormat();

        long negativeProgressedSize = -100L;

    void testNegativeProgressedSize() {
        FileSizeFormat format = new FileSizeFormat();

        long negativeProgressedSize = -100L;
        assertThrows(IllegalArgumentException.class, () -> format.formatProgress(negativeProgressedSize, 10L));
    }

    @Test
    void testNegativeProgressedSizeBiggerThanSize() {
        FileSizeFormat format = new FileSizeFormat();