我们如何（在单元测试时）断言是否在其他语句之前调用了一个语句

Question

we are using RhinoMocks to unit test our wpf app.

in one of the scenarios we have a method --

public void LetsAdd()
{
    _mockableInterface1.DoSomething();
    _mockableInterface2.DoSomethingElse();
}

Now when I try to unit test LetsAdd method, I can assert if both doSomething() and DoSomethingElse() were called or not. but can I somehow also test if they were executed in this very order?

so in other words can I write a test which fails if I swap the two method calls.. ?

Thanks

Answer 1

If you have preconditions, the test must fire them prior to the test logic. Never rely on the order of the tests. If there is particular data that needs to be set up for a test, you should set it up and then clean it after you are finished. This can be done in any testing library through setup and clean up methods. If your classes are fine grained enough, you can use the class setup and clean up methods, otherwise you have to focus on the test setup and clean up methods.

You could take the method of testing if things were set up (both methods fired?), but this can end up nullifying your test because one test was run in the "wrong" order. But since each test should be autonomous, there is not such thing as "wrong" order.

In your particular scenario, you should set it up to run in the order you needed tested. If all scenarios are valid, you need multiple tests. Here is what I mean by all scenarios (DS = DoSomething and DSE = DoSomethingElse):

Neither DS or DSE run DS only DSE only Both, DS first Both, DSE first

If different results are expected, by business rules, then you need all 5 tests. Rather than test for the order of the routines, your goal should be to be explicit about testing, forcing them to run in order.

If this cannot be accomplished in your tests, then I see two options:

1. Re-architecting the solution to remove the "randomness"
2. Adding some type of tracing for method order that can be queried