Mockito: 0 matcher expected, 1 recorded

Question

I got:- Invalid use of argument matchers! 0 matcher expected, 1 recorded: atInputStreamResource isr=new InputStreamResource(new ByteArrayInputStream(anyString().getBytes()));

Answer 1

anyString() is an argument matcher. It cannot be used in an "algebraic" sense (representing any value in your general program logic) or an "arbitrary value supplier" sense (in which it would supply an arbitrary string or other value to ensure your test works). Instead, it is meant to match your expectations against real interactions with your mock, either beforehand to determine the appropriate return value or behavior (when) or afterwards to assert that the call happened (verify).

Rules for matchers:

• Matchers come from static method calls on the ArgumentMatchers and AdditionalMatchers object. MockitoHamcrest.argThat and ArgumentCaptor.capture also count.
• You can only use it in calls to when, as in when(mock.method(argumentOrMatcher))).thenVerb or doVerb(...).when(mock).method(argumentOrMatcher), or verify as in verify(mock).method(argumentOrMatcher).
• The matcher has to replace the entire argument; you cannot call methods on the value returned by a matcher, and it cannot appear within any other call (aside from other matchers like AdditionalMatchers.and).
• Due to the way Mockito works, you'll need to be consistent: in a given call to when or verify, all of the arguments have to be matchers, or none of them can be matchers (in which case each is matched as if with Object.equals or ArgumentMatchers.eq).

Because you're using a matcher outside of those rules, there is 1 matcher recorded where there are 0 matchers expected. You'll need to write a test using your own arbitrary value where you currently have anyString. If your test still requires Mockito, you can then pass that same string into when or verify, or use a matcher like anyString there if needed.