Assertions with assertThat

I like to think I’m reasonably up-to-date with Java technologies but then I discovered something today that shows up that I’m still ignorant of a lot of available technology that’s out there. Today I ran across hamcrest which is now apparently part of junit 4.4 and above.

Basically it replaces the old assertEquals() & variants with an assertThat statement. ie:


assertThat([value], [matcher statement]);


Some examples:


assertThat(x, is(3));
assertThat(x, is(not(4)));
assertThat(responseString, either(containsString("color")).or(containsString("colour")));
assertThat(myList, hasItem("3"));


Basically all sorts of matchers are possible. The advantages here are improved failure reporting and a clearer expression of intent.

There’s some other interesting stuff built around this too – such as hamcrest collections. Take a look at this:


smiths = select(people, where(Person.class).getLastName(), equalToIgnoringCase("smith"));


Looks like good stuff to play around with over the next few days.