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Unit Testing

The Groovy Advantage

Groovy simplifies JUnit testing, making it more Groovy, in 3 ways.

  • JUnit is built into the groovy runtime, so you can script JUnit tests for your groovy and java classes using groovy syntax.
  • Groovy provides many additional JUnit assertion statements (see below)
  • Groovy unit tests are easily scriptable with Ant / Maven (see below)

See the following article Unit test your java code with groovy

Example

To write unit tests in groovy, you have to create a class extending groovy.util.GroovyTestCase.

import groovy.util.GroovyTestCase

class MyTest extends GroovyTestCase {
    void testSomething() {
        assert 1 == 1
    }
}

Groovy Test Assertions

Apart from the default assertions already available from the JUnit framework, GroovyTestCase also offers additionnal test assertions:

  • assertArrayEquals(Object[] expected, Object[] value)
  • assertLength(int length, char[] array)
  • assertLength(int length, int[] array)
  • assertLength(int length, Object[] array)
  • assertContains(char expected, char[] array)
  • assertContains(int expected, int[] array)
  • assertToString(Object value, String expected)
  • assertInspect(Object value, String expected)
  • assertScript(final String script) // assert that a script runs without exceptions
  • shouldFail(Closure code) // assert that an exception was thrown in that closure
  • shouldFail(Class clazz, Closure code) // the same but for a class

Details

By default Groovy unit test cases generate java bytecode and so are just the same as any other Java unit test cases. One thing to watch is often Ant / Maven look for *.java files to find unit tests with pattern matching, rather than *.class files.
There's an option in Maven to ensure you search for classes (and so find any Groovy unit test cases) via this property

maven.test.search.classdir = true

Once you've got this enabled you can use Maven goals to run individual test cases like this

maven test:single -Dtestcase=foo.MyGroovyTest

Running GroovyTestCases on the command-line

Since beta-6, you can also run your groovy tests (extending GroovyTestCase) on the command-line. It has simple as launching any other Groovy script or class:


groovy MyTest.groovy

Running GroovyTestCases in IDEs

Most IDEs support JUnit but maybe don't yet handle Groovy shame!.


Firstly if you compile the groovy code to bytecode, then it'll just work in any JUnit IDE just fine.

Sometimes though you want to just hack the unit test script and run from in your IDE without doing a build.
If you're IDE doesn't automatically recompile Groovy for you then there's a utility to help you run Groovy unit test cases inside any JUnit IDE without needing to run your Ant / Maven build.

The GroovyTestSuite class is a JUnit TestSuite which will compile and run a GroovyUnit test case


from a command line argument (when run as an application) or from the test system property when run as a JUnit test suite.

To run the GroovyUnitTest as an application, just do the equivalent of this in your IDE

java groovy.util.GroovyTestSuite src/test/Foo.groovy

Or to run the test suite inside your IDE, just run the GroovyTestSuite test with this system property defined

-Dtest=src/test/Foo.groovy

Either of the above can really help improve the development experience of writing Groovy unit test cases in IDEs that don't yet support Groovy natively.

Using normal scripts as unit test cases

You can write scripts like this

x = [1, 2, 3]
assert x.size() == 3

and use these scripts as unit test cases if you use the GroovyTestSuite class to run them as described above.

When the above script is compiled, it doesn't actually implement JUnit's TestCase and so needs a special runner so that it can be used inside a JUnit test framework. This is what GroovyTestSuite does, it detects scripts like the above and wraps them in a JUnit Test adapter so you can run scripts like the above as a unit test case inside your IDE