Groovy has excellent support for Testing with Unit Testing (GroovyTestCase adds extra capabilities to TestCase from JUnit 3.8.2) and Mocking capabilities built right in. Currently, there are no special Groovy extensions for JUnit 4 but it's easy to use so long as you are using Groovy 1.5+ and Java 5+ (a requirement for annotations/Junit 4.x). Here are some examples.
Make sure you are using at least Groovy 1.5 (we used 1.5.6) and JUnit 4.x (we used 4.4).
Let's test some of the built-in arithmetic operators in Groovy.
Our test class includes two tests additionIsWorking and divideByZero. The second of these is expected to fail with an ArithmeticException exception.
Running the test gives:
You can use the Hamcrest matchers that come with JUnit 4.4 and above like this:
The first test uses the matchers. You can see by the second test, that native Groovy assertions are usually going to do the job just as well if not better in the Groovy world.
JUnit 4.x includes the ability to have parameterized tests. Suppose we want to test the following program:
Here is what your code might look like. This example uses parameterization.
The output will look something like this:
You can use the experimental Theory tests from JUnit 4.4 and above as follows:
When run, this gives: