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Hamcrest

Posted by tomwhite on December 22, 2006 at 12:27 PM PST

In Literate Programming with jMock
I enthused about jMock's idea of constraints and flexible assertions.
Now the jMock team has released version 1.0 of Hamcrest,
the constraints part of jMock.

Hamcrest matchers (what were called constraints in jMock) are actually useful for more than just writing unit tests,
but it is their application in writing assertions
where they really shine and will probably see most use.

So now I can write

assertThat(a, equalTo(b))

or even

assertThat(a, is(equalTo(b)))

rather than JUnit's

assertEquals(b, a)

Apart from being more readable, assertThat takes any matcher as the second argument, so
I can combine matchers or even write my own
rather than creating an ever growing listof assertXxx methods. For example, I can say such things as

assertThat(collection, hasItem(anyOf(is(item1), is(item2))));

And since the matchers (and the assertThat method) are accessed using static imports,
I can use them in any test framework I like.

So why not read the tutorial
and give Hamcrest a go?

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