Unit Testing: Logging and Dependency Injection

Question

So regards logging from SO and other sites on the Internet the best response seems to be:

void DoSomething() {
    Logger.Log(\"Doing something!\");
    // Code.         


        

Answer 1

I would probably have a separate body of unit tests for the logger itself, to test out its various functions separately from everything else. In methods that are using the logger, I would just test that the logger was invoked (i.e. expect that it was called) with the right parameters. For example, if I have a method:

DoSomething()
{
    if (FatalErrorOccurred)
    {
        Logger.Log("Fatal Error", ErrorLevel.Fatal);
    }
}

I would write a test that shows the logger logged a fatal error message when FatalErrorOccurred was true. I would not, of course, test the contents of the error message itself, as that is very susceptible to change.