@Test public void testEmptyString() { String result = myMethod(""); assertNull(result); }
@Test public void testSetNullEmail() { User user = new User(); user.setEmail(null); assertNull(user.getEmail()); }In this example, we are creating a new `User` object, setting its `email` field to null, and then checking that the `getEmail` method also returns null. The `assertNull` method ensures that the test passes if the `getEmail` method returns null. The package library for the `assertNull` method is `org.junit`. This package is part of the JUnit testing framework for Java.