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Monday, July 12, 2010

Adding JUnit / Hamcrest Functionality & Sources To Netbeans

Adding JUnit / Hamcrest Functionality & Sources To Netbeans

Im using JUnit4.5 in Netbeans for my unit testing (which in itself I wont go into detail in this blog post but JUnit and Unit Testing are things that are highly important and that I am all for the use of). Now while the latest JUnit version is up to 4.8.1/4.8.2 currently (20100712) Netbeans is not yet by default implemented to use this so for now Im using the version Netbeans comes with, 4.5, and It may be a future blogpost to upgrade Netbeans to the latest JUnit version (not tonight tho cos its 2:44am, Im still writing about Hamcrest and I got work tommorrow). Furthermore JUnit as of version 4.4 uses a library called Hamcrest internally. This is for performing a number of cool things whereby the assert* set of methods in JUnit are extended by the method assertThat():,%20org.hamcrest.Matcher%29

using a parameter called a Matcher. Using the Hamcrest tutorial as a starting point Im going to go through and describe the Hamcrest library and its functionality. The tutorial I mention along with a number of other links I found interesting are at the end of this post....though you first have to read it before you get to them of course :-).

Now Matchers as provided by Hamcrest allow us to test in a more fluent, spoken word declarative sort of a way and the Hamcrest library comes with a number of useful matchers. Here are some of the most important ones (and its important to note that a lot of these only come with the latest version of hamcrest)

  • anything - always matches, useful if you don't care what the object under test is
  • describedAs - decorator to adding custom failure description
  • evaluate - matches if a specified Boolean condition evaluates to true.
  • given - conditionally matches a value or Matcher
  • isA - matches a specific type
  • throws - matches if a function throws the given exception

  • allOf - matches if all matchers match, short circuits (like &&)
  • anyOf - matches if any matchers match, short circuits (like ||)
  • not - matches if the wrapped matcher doesn't match and vice versa

  • equalTo - compares objects using ==
  • sameInstance, strictlyEqualTo - compare objects using ===
  • hasProperty - checks that a property exists and, optionally, that it matches the provided matcher
  • hasProperties - similar to hasProperty, but accepts a dictionary of properties and their associated matchers
  • hasPropertyChain - checks that a chain of properties exist and optionally that the value matches a provided value
  • instanceOf - test type
  • notNullValue, nullValue - test for null

  • array - test an array's elements against an array of matchers
  • arrayWithSize - match an array's size against a number
  • hasItem, hasItems - test a collection contains elements
  • everyItem - test that a matcher matches every item in an array
  • sortedBy - test an array's elements are sorted a single field
  • sortedByFields - test an array's elements are sorted by multiple fields

  • closeTo - test that values are close to a given value
  • greaterThan, greaterThanOrEqualTo, lessThan, lessThanOrEqualTo - test ordering
  • between - test that a value is between two given values

  • containsString, endsWith, startsWith - test string matching
  • re - text matches a regular expression

  • dateAfter, dateAfterOrEqual, dateBefore, dateBeforeOrEqual - date comparisons
  • dateBetween - test that a date is within a given range
  • dateEqual - tests dates for equality

This allows for JUnit tests which are a lot more clearer in their intent. Ill give some examples of this below:

assertThat("chocolate chips", theBiscuit.getChocolateChipCount(), equalTo(10));
assertThat(someObject, notNullValue());

As you can see these are much clearer than the usual case of simply comparing to get a boolean result. In these cases it is much clearer as to the intent of the test even though it For example, the 'is()' matcher is a wrapper that doesn't add any extra behavior to the underlying matcher. The following assertions are all equivalent:

assertThat(theBiscuit, equalTo(myBiscuit));
assertThat(theBiscuit, is(equalTo(myBiscuit)));
assertThat(theBiscuit, is(myBiscuit));

The last form is allowed since is(T value) is overloaded to return is(equalTo(value)). These allow the test statements to 'read' like proper english.

Now Hamcrest has other features, including extensions to Matchers through your own customer matchers, and a bunch of other features (see links below). However, when I went to look at a JUnit test and I added some code to it to use these cool features, using the Netbeans functionality to go to source didnt work as there is no source attached to the code. What gives? Well I did the following.

  1. Download hamcrest-all.jar and junit4.8.2.jar
  2. Then first of all i customised my junit4.5 lirary. I went to sources and added from junit4.8.2 the directory temp.hamcrest.source to the sources for junit4.5
  3. Now while this is fine for the Unit Matches and using Hamcrest in JUnit I was curious about ALL the Hamcrest code and so I also then went and created a new Library called Hamcrest1.1 and added the download jar as the path, source and javadoc as this contains all 3 (the .class files are ther alongside the .java) and then added this to my project which now allows me to play around with Hamcrest.
So with these changes I can now not only use Hamcrest with JUnit, but I can now go and browse to the source as well which I always want to be able to do as I love to be able to go digging around in the implementation and see others code and how tools I love work.


Project -
JUnit Release Notes -
Tutorial on Hamcrest -

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