Java Hamcrest : Collection contains item of type

Question

I'd like to assert that List<Achievement> contains a member of type TestAchievement.

Here's my assertion:

List<Achievement> achievements; // Populated elsewhere assertThat(achievements,hasItem(isA(TestAchievement.class))); 

This doesn't compile, reporting the error:

The method assertThat(T, Matcher) in the type Assert is not applicable for the arguments (List, Matcher<Iterable<TestAchievement>>)

What's the correct syntax for this type of assertion using Hamcrest?

Answer 1

Thanks for all the help.

The posts here suggested it was a defect with Hamcrest, so I headed over to the hacmrest site to register a bug, whien I discovered that the mvn / ivy dependency declaration I was using was out-of-date, giving me an old version of Hamcrest.

This bug exists with 1.1, which is the latest if declared using

<dependency org="org.hamcrest" name="hamcrest-all" rev="1.1"> 

However, the correct depedency declaration is:

<dependency org="org.hamcrest" name="hamcrest-library" rev="1.3.RC2"/> 

Updating to this solved the issue. The syntax used in my test is:

 assertThat(achievements, hasItem(isA(TestAchievement.class))); 

Answer 2

There is a bug in Java 6 that relates to this.

This code will throw various errors such as "cannot find symbol..."

assertThat(achievements, hasItem(isA(TestAchievement.class))); 

The work around for this is to declare the matcher as a variable and then reference that variable. It is important to note that the type of the variable, specifically the generics section, is very important for this to work.

Matcher<Iterable<? super TestAchievement>> matcher = hasItem(isA(TestAchievement.class)); assertThat(achievements, matcher); 

Interestingly if you use instanceOf() instead of isA() you once again run into issue. (although if you ignore the warnings this might just work for you anyway.) Expanding on the previous fix you can use:

Matcher<TestAchievement> itemMatcher = Matchers.instanceOf(TestAchievement.class); Matcher<Iterable<? super TestAchievement>> matcher = hasItem(itemMatcher); assertThat(achievements, matcher);