Need help on a unit testing on handling the empty string, pretty new to java.

@Test void should_handle_null_string() { assertNull(ClassName.methodName(null)); }

@Test void should_handle_empty_string() { assertTrue(ClassName.methodName("").isEmpty()); }

For the first test, I can successfully use "if (input == null) return null;" to pass. However, I encountered the problem on the second one. Since the output of the method is String, so when I tried using the following:

if (input.equals("")) return String.valueOf(true); 

It cannot pass. The error shows that "expected: but was: ". I'm confused about it.

"