public String getString(@NotNull final String key, @Nullable final String defaultValue) {
        return System.getProperty(key, props.getProperty(key, defaultValue));
    }
@Test
    public void testGetString() {
        String key = Settings.KEYS.NVD_API_DATAFEED_VALID_FOR_DAYS;
        String expResult = "7";
        String result = getSettings().getString(key);
        Assert.assertTrue(result.endsWith(expResult));
    }