We’ve been discussing the differences between stubs and mocks, along with the fact that many software testers may initially assume the two are the same concept. But as we have learned, mocks and stubs are not synonyms; they are two different techniques used within unit testing.
I wanted to learn more about some specific differences between stubs and mocks, such as potential advantages and disadvantages of using each of these techniques. Wojciech Bulaty has an informative article on the subject. Before getting into the pros and cons of each aforementioned technique, Bulaty explains the main concepts of stubs, mocks, and service virtualization.
He asserts that stubs use hardcoded data within the testing program itself, where the tests depend on this data. Based on Bulaty’s description of stubs, it seems it would be most beneficial to me to apply stubs when testing simpler code where no more than minimal implementation of an interface is required.
Mocks on the other hand seem to be most useful in situations for larger, more complex tests to “verify output against exceptions.” In my opinion, mocks ought to be used in addition to stubs to further satisfy the integrity of our testing. For instance, mocks may produce findings that stubs could not, due to the limitations of the hardcoded data within stubs. On the other hand, I feel it may be useful to use stubs as well, to help compare its findings with that of the mocks within our tests.
Bulaty introduces a third method to use within our unit tests: service virtualization. I found this particularly interesting because we haven’t discussed much about service virtualization in class yet, and this article helped me learn more about it. He explains that service virtualization supports testing through multiple protocols, and employs “test doubles” which are usually offered as Software as a Service (SaaS). It seems to me that service virtualization relies more on recorded data from a wide scope of different projects, whereas stubs and mocks are typically written by developers of their own projects.
My main takeaway from this article was recognizing some differences in particular between mocks, stubs, and service virtualization that were previously a bit unclear to me. Whereas stubs seem to concentrate on state verification, mocks tend to be more focused on behavior interactions within our code. I also learned which testing techniques may be most appropriate in regards to the particular code we are testing. For instance, if I am testing simpler tests with limited resources, based on what I’ve learned from this article, I will likely use stubs for my testing. But for larger, more complex tests, I feel I ought to implement mocks within my testing as well. Finally, when I am involved in large scale projects during my professional career, Bulaty’s article has convinced me that I should look into using service virtualization in addition to stubs and mocks when performing unit testing.
From the blog CS@Worcester – Jason Knowles by Jason Knowles and used with permission of the author. All other rights reserved by the author.
