Owin TestServer logs multiple times while testing - how can I fix this? - web-services

Question

I'm trying to write unit tests for an OWIN service, but any log statements in my tests start duplicating once I run the tests all at once and really make the log output on the build server useless due to all the noise. I've distilled the problem down to a very simple repro:
[TestFixture]
public class ServerTest
{
[Test]
public void LogOnce()
{
using (TestServer.Create(app => { }))
{
Debug.WriteLine("Log once");
}
}
[Test]
public void LogTwice()
{
using (TestServer.Create(app => { }))
{
Debug.WriteLine("Log twice");
}
}
}
If I run one test at a time I get the expected output:
=> ServerTest.LogOnce
Log once
=> ServerTest.LogTwice
Log twice
If I run the tests all at once I get:
=> ServerTest.LogOnce
Log once
=> ServerTest.LogTwice
Log twice
Log twice
Initializing the TestServer once will solve the problem, but I am looking for a solution that allows me to continue instantiating as many TestServer instances as I choose.

Answer 1

This post points out how HostingEngine is defaulting on the TraceListener and ways to disable this:
TraceListener in OWIN Self Hosting
With that insight, I traced through the source code of TestServer.Create and confirmed that it is internally creating a HostingEngine which turns on a TraceListener that ultimately outputs results to the console. I have confirmed the highest voted (at the time of this writing) fix on that page works for the TestServer and believe the other solutions there are also excellent choices.
It was very time consuming and annoying having to figure this out. It is difficult to discover and non-obvious to wire up an opt-out. An opt-in solution would be better.