Not using testing frameworks like MockK or Mockito seems to be becoming more and more popular. I decided to try this approach. So far so good, returning fake data is simple. But how do I verify that a function (that does not return data) has been called? Imagine having a calss like this:
class TestToaster: Toaster {
override fun showSuccessMessage(message: String) {
throw UnsupportedOperationException()
}
override fun showSuccessMessage(message: Int) {
throw UnsupportedOperationException()
}
override fun showErrorMessage(message: String) {
throw UnsupportedOperationException()
}
override fun showErrorMessage(message: Int) {
throw UnsupportedOperationException()
}
}
With MockK I would do
verify { toaster.showSuccessMessage() }
I do not want to reinvent a wheel so decided to ask. Finding anything on Google seems to be very difficult. Since this is a thing, I assume the point would be to totally remove mocking libraries and everything can be done without them.
A lot of people seem to be suggesting the very straight forward solution for this, which totally makes sense. I decided to go a bit fancy and achieve this syntax:
verify(toaster = toaster, times = 1).showErrorMessage(any<String>())
.I created simple Matchers:
Added a map to store call count for each method to my TestToaster where the key is the name of the function and value is the count:
private var callCount: MutableMap<String, Int> = mutableMapOf()
Whenever a function gets called I increase current call count value for a method. I get current method name through reflection
In oder to achieve the "fancy" syntax, I created inner subcalss for
TestToaster
and averify
function:That function sends current
toaster
instance to the inner subclass to create new instance and returns it. When I call a method of the subclass in my above syntax, the check happens. If the check passes, nothing happens and test is passed, if conditions not met - and exception is thrown.To make it more general and extendable I created this interface:
Here is the complete class:
I have not tested this extensively and it will evolve with time, but so far it works well for me.
I also wrote an article about this on Medium: https://sermilion.medium.com/unit-testing-verify-that-a-method-was-called-without-testing-frameworks-like-mockito-or-mockk-433ef8e1aff4