Hamcrest: Unclear exception message?

Question

Although English is not my mother tongue, I still think that the following error message from Hamcrest is wrong.

I have the following validation method:

private void validateReturnedCode() {

    List<HTTPStatusCodes> expectedStatusCodesList = requestData.getExpectedHttpCodes().getStatusCodes();
    HTTPStatusCodes actualReturnedCode = fromCode(response.getStatusCode());
    assertThat(expectedStatusCodesList, hasItem(actualReturnedCode));
}

Suppose expectedStatusCodesList is {REDIRECT_FOUND} and actualReturnedCode is OK.

So obviously there should be an exception here, but I cannot understand the logic of the error message:

java.lang.AssertionError: 
Expected: a collection containing <OK>
     but: mismatches were: [was <REDIRECT_FOUND>]

Wouldn't it be better if it was:

java.lang.AssertionError: 
Expected: a status code one of <REDIRECT_FOUND>
     but: mismatches were: [value was <OK>]

?

The expectation was to receive REDIRECT_FOUND but actually I received OK!

If I get it wrong, could you please explain?

Answer 1

The first argument for the assertThat() method states, that it must be the "actual" value you get:

assertThat

public static <T> void assertThat(T actual,
                                  Matcher<? super T> matcher)

So, your actualReturnedCode must be in the front. Use the isIn() match to check if a value is inside a collection:

assertThat(actualReturnedCode, isIn(expectedStatusCodesList));