CODEWITHSUNDEEP
unit-testinggroovymocking
kaskelotti
kaskelotti

Reputation: 4832

Mock a single method of unit under test in Groovy

I have a simple class like

class SomeClass {
  def foo() {
    def bar= bar()
    switch( bar ) {
      return something based on format
    }
  }

  def bar() {
    return someValue
  }
}

I've already written complete unit tests for the bar(). Now I need to write unit tests for foo() which is heavily dependant on the use of bar() method. I don't want to duplicate the setup phase as done for bar(), so I'd like to mock it by simply returning values I want.

I'm aware that Groovy supports this sort of "mocking" easily by simply defining it like SomeClass.property = "Hello World". Also, this can be done with collaborators as SomeClass.service = myMockedService. But I've not found a way to accomplish this with methods inside the unit under tests. Is there?

I tried with MockFor as in

def uut = new MockFor( SomeClass )
uut.demand.bar{ /* some values */ }
uut.use {
  assert uut.foo() == expected
}

but it gives me 

groovy.lang.MissingMethodException: No signature of method: groovy.mock.interceptor.MockFor.foo() is applicable for argument types: () values: []

UPDATE

In fact, I came up with a simple solution of using sub-classing. In the test method I create a subclass of SomeClass where I override the method I wish to mock/stub. After this, using an instance of the subclass gives me what I need.

This seems a bit rough, though. Any other suggestions on this?

Upvotes: 0

Views: 2805

Answers (1)

Dónal
Dónal

Reputation: 187399

If you want to mock the value returned by bar() for a single instance of SomeClass you can use metaprogramming. Try the following in the Groovy console:

class SomeClass {
  def foo() {
  }

  def bar() {
    return 'real value'
  }
}

def uut = new SomeClass()

uut.metaClass.bar = {
  return 'mock value'
}

assert 'mock value' == uut.bar()

If you want to mock bar() for all instances of SomeClass, replace this:

uut.metaClass.bar = {
  return 'mock value'
}

with:

SomeClass.metaClass.bar = {
  return 'mock value'
}

Upvotes: 3

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