How can I test private methods with DUnit?

Question

I have a class that I am unit testing into with DUnit. It has a number of methods some public methods and private methods.

type
  TAuth = class(TDataModule)
         


        

Answer 1

It is a little hacky, but I think this is the simplest and clearer approach. Use this conditional compilation directive:

  {$IfNDef TEST}
  private
  {$EndIf}

Your unit test project must define TEST in project → conditional defines. Without a visibility specification, they become published.

Beware: if the private visibility isn't the first one in the class declaration, it will get the previous definition. A safer way, but more verbose and less clear, would be:

  private
  {$IfDef TEST}
  public
  {$EndIf}

This has a lot of advantages over the subclassing or other approaches:

• No extra complexity: no extra classes in your code.
• Nobody can "mistakenly" subclass and override your class: you preserve your architecture.
• When you say a method is protected, you somewhat expect that it will be overridden. You are telling this for who is reading your code. A protected method that shouldn't be overridden will confuse your code readers, breaking my first programming principle: "Code must be written to be read by other human beings."
• DUnit is in their own unit, not included everywhere.
• You don't touch messy RTTI.

I think it is a clearer solution, and better than the selected answer.

When I use this, I also configure the test project to put the build objects in a different directory of the main project. This prevents the binaries with the TEST directive to mix with the other code.