@Test
public void testGetSysProperty() {

    Assertions.assertNull(sysConfig.getInternalProperty(MOCK_KEY));
    Assertions.assertFalse(sysConfig.containsKey(MOCK_KEY));
    Assertions.assertNull(sysConfig.getString(MOCK_KEY));
    Assertions.assertNull(sysConfig.getProperty(MOCK_KEY));
    System.setProperty(MOCK_KEY, MOCK_STRING_VALUE);
    Assertions.assertTrue(sysConfig.containsKey(MOCK_KEY));
    Assertions.assertEquals(MOCK_STRING_VALUE, sysConfig.getInternalProperty(MOCK_KEY));
    Assertions.assertEquals(MOCK_STRING_VALUE, sysConfig.getString(MOCK_KEY, MOCK_STRING_VALUE));
    Assertions.assertEquals(MOCK_STRING_VALUE, sysConfig.getProperty(MOCK_KEY, MOCK_STRING_VALUE));
}