Legacy Code to Testable Code #6: Add Overload

This post is part of the “Legacy Code to Testable Code” series. In the series we’ll talk about making refactoring steps before writing unit tests for legacy code, and how they make our life easier. Other posts include:

The Legacy Code To Testable Code Series

In the last post, I’ve talked about Extract Class refactoring pattern, and that sometimes in order to do that, we might want to change the signature of a method.

Turns out adding an overload helps in other cases as well.

We used a “setter” to expose to the unit test and inject internal state before. Another option is to add a controllable overload to bypass the internal state.

Let’s look at this code:

public Bool isSameStreet(String newStreet) {
return newStreet == this.currentAddress.getStreet();
}

public Bool isSameStreet(String newStreet) {
    return isSameStreet(newStreet, this.currentAddress.getStreet());
}

public Bool isSameStreet(String newStreet, String currentStreet) {
    return newStreet == currentStreet();
}

The new overload is more controllable. We can stop there, but if our logic code does not rely on state anymore, why not use Extract Class refactoring pattern?

public Bool isSameStreet(String newStreet) {
    return StreetValidator.areEqual(newStreet, this.currentAddress.getStreet());
}

Time to wrap up the series. So next time, in the last chapter – using dependency injection framework.