I’ve been given the task of refactoring some legacy code, the main reason is to add (but I’m a firm believer that testable code is better code, so we’re trying to reduce technical debt too). The current code is a big mess, there’s a handfull of classes, one is 6000 lines, and has methods 300 lines long etc.

First thing I’ve been doing is splitting out data access for mocking, that’s a nice independent thing. However, I’ve noticed that these classes, buy their nature, tend to have one ‘entry’ point, say a single method ProcessData.

Theoretically this could be the only public method. But I definately want to test these methods independently:

public  DataProcessor {

    public void ProcessData(...) {
        // this is the 'enty point'
        if (IsAlreadyProcessed())

        for (...) {

    public void ProcessSubData(...) {
        if (IsDataTypeA)
        else if (IsDataTypeB)

    public bool IsAlreadyProcessed(...) {
        // do some complex stuff here I want to test

    public void ProcessWithMethodA(...) {
        // something I definately want to test separately

    public void ProcessWithMethodB(...) {
        // something I definately want to test separately

the ‘root’ method will be tricky, and involve some very hefty objects given the scope of all it’s doing. Ideally I want to test the other methods, then just test that ProcessData calls them.

Basically, it has a dependency on itself – should I a mock version of DataProcessor into itself so I can test only sections of it?

The other option would be to split out the other Process methods into a separate class, and have that mockable and injectable into the DataProcessor – but to do this for each ‘level’ that these methods call each other would require a few or more extra classes that only exist to explode it out so it can be tested.

Source link https://sqa.stackexchange.com/questions/30704/testing---inject-a-mock-of-itself-or--into-new-cl


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