Wednesday, March 20, 2013

Clojure: Expectations Ignore A Variable Number Of Args In An Interaction Test

Over the past year I've written the same test a few times.

This test accomplishes what I'm looking for when I write it - verification that my-fn isn't called. However, it doesn't prevent me from future regressions where my-fn is called with 0, 2, or 2+ arguments. After being bitten by this issue a few times I decided to add an argument matching function that will accept any value for the argument at it's index, and any value for all of the arguments at a greater index. This argument matching function is anything&

The following example is similar to what's above, except any call to my-fn will result in a failure

My original intent was to protect against the scenario I described above*; however, what I ended up with is actually flexible enough to allow me to test other situations as well. For example, I've often found myself testing that a log message was written at a certain level, but not being interested in testing the actual message. The logging I'm working with allows a variable number of arguments, so anything& is perfect for verifying that no matter what args are passed in, the tests passes as long as the level is set correctly.

The anything& matching function gives me an extra bit of flexibility that can come in handy at times.

*which is similar to verifyZeroInteractions in mockito

Tuesday, March 19, 2013

Clojure: Expectations Interaction Tests For Java Objects

I recently ran into some code that forced me to integrate with a Java library. While using the library I found myself wanting to do a bit of interaction testing, which I've historically done with Mockito. As a result, I added the ability to do interaction based tests on mock Java objects, directly in expectations.

Hopefully the code is what you'd expect.

The previous example creates a mock Runnable in an expect-let, expects the run method to be run, and then calls the run method of the mock. This test is worthless in a real world context, but it's the simplest way to demonstrate the syntax for creating a mock & specifying the interaction.

The mock function defined in erajure, a minimal wrapper around mockito. All of the "times" arguments are the same as what's available for function interaction tests, examples can be found here.