The concept in testing and test doubles in spies is you’ll be trying to verify that a specific thing was run. A stub creates a test double where I’ll tell it we have this test object that’s pretending to be another thing, I know that I’m expecting specific methods to be called, and when they are, I’m expecting specific results to come back.Īnother type of test double people sometimes use is spies. You just need it to exist to satisfy a parameter check as it’s passed around. A dummy creates a mock of an object that just has to stand in because you need that type of object to exist as a dependency, not because you need it to do anything. There are two types of test doubles the PHP community mostly uses: dummies and stubs. In the PHP community, these are all known as mocks because the tools says get mocks. Can you talk about the differences between Doubles, Dummies, Stubs, Spies, Mocks & Fakes and when to use each one? However, excessive mocking is a sign there is a problem with the code itself. Altogether, I mock anything I can’t control, and I try to look and see if there are ways to create a real version of a dependency with the test for things I can control. database connections, calls to remote API) and puts them into a proper state as a dependency. I do use mocks because mocks are the only way to test third-party things that aren’t under your control (e.g. It means you have a test scenario that’s really complicated and the object you’re trying to test can’t do it without a lot of help. Having to do excessive mocking is a test smell. If you start looking at what the object is responsible for doing and how the methods are supposed to be manipulating the state of the object, you’ll quickly realize you have some design mistakes. Everyone is familiar with the “God” object idea, which has large classes with 20~30 methods on them. If you’re having to do a lot of mocks in order to let a testing scenario work, chances are you have an object that you’re testing that is doing too much. I believe mocks are a really good way to tell if your code is overly complex. The text below is a summary done by the Codementor team and may vary from the original video and if you see any issues, please let us know!ĭo you advocate a lot of mocks? If so, do you ever get the feeling that you aren’t actually testing anything? How do you get past this feeling? If they don't supply a suffix, we'll go for the highest weighted Accept header we can support.Codementor PHP expert Chris Hartjes is a frequent conference speaker advocating testing, and he co-organized the GTA PHP User Group.Ĭhris recently joined us during Codementor’s Office Hours, and some of the users asked about testing doubles. We will give the highest weight to the file suffix on the end of the URI - if a client requests /foo.json, we'll assume they want JSON, even if the Accept header only specifies application/xml. Its job in my imaginary API is to read the request path and headers and decide a) whether the client has requested a valid format at all and b) what is the highest priority supported format they have asked for. Imagine a service to testįor the sake of argument, I've written a simple content negotiator class for an API which can return data in multiple formats. This is the contention I want to explore in today's blog post. My contention, however, is that these cases are a rare exception, that - particularly in the PHP community but also more broadly - mocks are vastly overused and over-relied on, have a tendency to lead to badly constructed, uninformative, brittle tests and are simply neither needed nor preferable in the majority of cases. Sometimes we have complex business logic interacting with dependencies in such a way that it's difficult in practice to test without making direct assertions about how the dependency was used. This is, on occasion, a legitimately useful thing to do. In PHP, they are instantly recognizable by code which looks like this: $mockFoo->expects($this->once())->method('bar')->with($this->equalTo('baz')) Mocks are a type of test double which make assertions on how the object will be used what methods will be called, what order, how many times, with what parameters. If you've written a unit test, you've (almost definitely) written mocks. If you've ever seen a unit test, you've seen mocks.
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