@Test
    public void test_get_emptyFile() throws Exception {
        writeTestFile("");

        OptionalEntity<CharMappingItem> result = charMappingFile.get(1L);
        assertFalse(result.isPresent());
    }

    // Test get method with valid data
    @Test
    public void test_get_validData() throws Exception {
        writeTestFile("a,b => c\nd,e => f\n");