The following test is flaky: https://github.com/open-telemetry/opentelemetry-dotnet-contrib/blob/c5b0a44995be3544c74652ffa259a0f94dbce955/test/OpenTelemetry.Instrumentation.AspNet.TelemetryHttpModule.Tests/ActivityHelperTest.cs#L87 It appears that sometimes `ActivityHelper.StartAspNetActivity()` returns `null`.