public void test_getTypes_empty() {
        String[] types = fileTypeHelper.getTypes();
        assertNotNull(types);
        assertEquals(0, types.length);
    }

    @Test
    public void test_add_overwrite() {
        fileTypeHelper.add("application/pdf", "pdf");
        assertEquals("pdf", fileTypeHelper.get("application/pdf"));

        fileTypeHelper.add("application/pdf", "document");