How to test asp.net core built-in Ilogger

Question

I want to verify some logs logged. I am using the asp.net core built-in ILogger, and inject it with the asp.net core built-in DI:

private readonly ILogger<         


        

Answer 1

As @Nkosi've already said, you can't mock an extension method. What you should mock, is the ILogger.Log method, which LogError calls into. It makes the verification code a bit clunky, but it should work:

MockLogger.Verify(
    m => m.Log(
        LogLevel.Error,
        It.IsAny(),
        It.Is(v => v.ToString().Contains("CreateInvoiceFailed")),
        It.IsAny(),
        It.IsAny>()
    )
);

(Not sure if this compiles, but you get the gist)