@Test
public void testOSNPE() {

    String oldProperty = System.getProperty("os.name");
    try {
        if (oldProperty != null) {
            System.clearProperty("os.name");
            assertNull(System.getProperty("os.name"));
        }
        OS.isLinux();
        
    } finally {
        if (oldProperty != null) {
            System.setProperty("os.name", oldProperty);
            assertEquals(oldProperty, System.getProperty("os.name"));
        }
    }
}