ILogger and IOptions in .NET unit tests: NullLogger, FakeLogger and Options.Create

// ======================================================================
// Q: How do you handle ILogger and IOptions in unit tests?
//
// Use NullLogger<T>.Instance when the logs don't matter, FakeLogger<T>
// (Microsoft.Extensions.Diagnostics.Testing) when you need to assert that
// something was logged, and Options.Create to build options without any
// configuration.
// ======================================================================

// You don't care about the logs
var sut = new PriceSync(repo, NullLogger<PriceSync>.Instance);

// You want to verify that a warning was logged (Microsoft.Extensions.Diagnostics.Testing)
var logger = new FakeLogger<SyncOrderToErpHandler>();
// ... act ...
Assert.Equal(LogLevel.Warning, logger.Collector.LatestRecord.Level);
Assert.Contains("rejected by ERP", logger.Collector.LatestRecord.Message);

// Options without configuration
var options = Options.Create(new ErpOptions { BaseUrl = "http://erp/", AttemptTimeoutSeconds = 5 });