Aspnetcore: How to test asp.net core built-in Ilogger

[arielcloud]

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 _logger;

public InvoiceApi(ILogger<InvoiceApi> logger)
{
    _logger = logger;
}

then I use it like: _logger.LogError("error));

I tried to mock it (with moq) as usual by:

MockLogger = new Mock<ILogger<InvoiceApi>>();

and inject this in the service for test by:

new InvoiceApi(MockLogger.Object);

then tried verify:

MockLogger.Verify(m => m.LogError(It.Is<string>(s => s.Contains("CreateInvoiceFailed"))));

but it throw:

Invalid verify on a non-virtual (overridable in VB) member: m => m.LogError

So, how can I verify this logs logged?

I asked this in SO and the answer I got was that I need to wrap the ILogger in my own interface.

But I was sure that the main objective of ILogger is to be the wrapper for logs, so is not it'll be better to do it testable?

thanks

[pranavkm]

LogError is an extension method on ILogger. ILogger.Log is the method you want to mock.

[davidfowl]

Extension methods strike again!