How to write properly a groovy unit test with jUnit?

Question

I am getting started with Groovy and I don't know how to write unit tests over my methods written on a class. For example:

One my methods on sample.groovy :

class sample {
   
   def length = { list -> list.size() }
   ...

}

So, I have one class named sampleTest.groovy :

class sampleTest extends GroovyTestCase {

    @Test
    public void testLength() {
        def result = length([2, 3, 8, 9, 0, 1, 5, 7])
        assert result == 8
    }

}

BTW, when I run this test, an error throws to me:

groovy.lang.MissingMethodException: No signature of method: sampleTest.length() is applicable for argument types: (java.util.ArrayList) values: [[2, 3, 8, 9, 0, 1, 5, 7]]
    at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.unwrap(ScriptBytecodeAdapter.java:55)
    at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:78)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:49)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:133)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:141)
...

Solution

length is a (non-static) property of the sample class. Because it's non-static, you need to evaluate it against a sample instance, e.g.

class sampleTest extends GroovyTestCase {

    @Test
    public void testLength() {
        def result = new sample().length([2, 3, 8, 9, 0, 1, 5, 7])
        assertEquals 8, result
    }
}

Also, you should try to use the assertion methods provided by GroovyTestCase such as assertEquals, assertNotNull, assertTrue, rather than the assert keyword.

You should also capitalize your class names, e.g. Sample and SampleTest rather than sample and sampleTest.

Comments

[Admin]

Thanks a lot, your answer was very useful for me.

[TheOperator]

The official Groovy homepage advertises the use of power assertions (assert keyword) for testing.