Jakub is a Java EE developer since 2005 and occasionally a project manager, working currently with Iterate AS. He's highly interested in developer productivity (and tools like Maven and AOP/AspectJ), web frameworks, Java portals, testing and performance and works a lot with IBM technologies. A native to Czech Republic, he lives now in Oslo, Norway. Jakub is a DZone MVB and is not an employee of DZone and has posted 154 posts at DZone. You can read more from them at their website. View Full User Profile

hasProperty, the Hidden Gem of Hamcrest (and assertThat)

10.17.2011
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If you got used to JUnit 4′s assertThat with various matchers (of course you will need junit-dep.jar and hamcrest.jar to get the full set instead of the small subset integrated in junit.jar), make sure you don’t overlook the matcher hasProperty. It is very useful if you have non-trivial objects and cannot use some more flexible language like Groovy for your unit tests.

The advantage of hasProperty is that it allows you to check a particular property (or more properties with allOf) of an object while ignoring the others – pretty useful if the object has 20 properties and checking just one is enough for you. (Admittedly, an object with 20 properties is an abomination but hey, that’s the real legacy word!)

Example – check that collection contains two Images with some file names:

assertThat("Expected images", (Iterable<Object>) hotel.getImages()
  , containsInAnyOrder(hasProperty("filename", is("radisson1.jpg"))
     , hasProperty("filename", is("radisson2.jpg"))));

The failure message in this case isn’t as clear as I might wish but still this is the best solution I can think of.

From http://theholyjava.wordpress.com/2011/10/15/hasproperty-the-hidden-gem-of-hamcrest-and-assertthat/

Published at DZone with permission of Jakub Holý, author and DZone MVB.

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