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Suppose we are trying to test the following application:

We might be tempted to replace logger and factory with Groovy's <a class="confluence-link" href="/display/GROOVY/Groovy+Mocks" data-linked-resource-id="59174" data-linked-resource-type="page" data-linked-resource-default-alias="Groovy Mocks" data-base-url="http://docs.codehaus.org">built-in mocks</a>, but it turns out that Maps or Expandos are often sufficiently powerful enough in Groovy that we don't need full blown dynamic mocks for this example.

Instead of a mock for logger, we can use an Expando as follows:

Here the expected behaviour for our production code is captured within a Closure. (When using TDD, this closure would force the production code we saw in our original code to be created.)

Instead of a mock for factory, we can use a simple map as follows:

Here, <code>businessObj</code> is the object we want the factory to return, though in general this could be a Closure similar to what we did for the Expando above.

Putting this altogether yields (after some refactoring) the following complete test:

<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
class MyAppTest extends GroovyTestCase {
 void testDoesBusinessLogic() {
 // triangulate
 checkDoesBusinessLogic "case1"
 checkDoesBusinessLogic "case2"
 }
 private checkDoesBusinessLogic(param) {
 def logger = setUpLoggingExpectations(param)
 def businessObj = setUpBusinessObjectExpectations(param)
 def factory = [instance: businessObj]
 def cut = new MyApp(logger:logger, factory:factory)
 cut.doBusinessLogic(param)
 }
 private setUpLoggingExpectations(param) {
 def shouldProduceCorrectLogMessage =
 { msg -> assert msg == 'Something done with: ' + param }
 def logger = new Expando()
 logger.log = shouldProduceCorrectLogMessage
 return logger
 }
 private setUpBusinessObjectExpectations(param) {
 def shouldBeCalledWithInputParam = { assert it == param }
 def myObj = new Expando()
 myObj.doSomething = shouldBeCalledWithInputParam
 myObj.doSomethingElse = shouldBeCalledWithInputParam
 return myObj
 }
}
</pre></td></tr></table>

See also: <a class="confluence-link" href="/display/GROOVY/Developer+Testing+using+Closures+instead+of+Mocks" data-linked-resource-id="66905" data-linked-resource-type="page" data-linked-resource-default-alias="Developer Testing using Closures instead of Mocks" data-base-url="http://docs.codehaus.org">Developer Testing using Closures instead of Mocks</a>