NUnit sometimes ends with "unable to locate fixture"

Question

The NUnit-console 2.6.3 sometimes prints out the following error message instead of running tests. Here is excerpt from my Jenkins test build logs:

00:05:02.982 Process 'nunit-console-x86' [PID 3684] has begun profiling.
00:05:03.698 NUnit-Console version 2.6.3.13283
00:05:03.698 Copyright (C) 2002-2012 Charlie Poole.
00:05:03.698 Copyright (C) 2002-2004 James W. Newkirk, Michael C. Two, Alexei A. Vorontsov.
00:05:03.698 Copyright (C) 2000-2002 Philip Craig.
00:05:03.698 All Rights Reserved.
00:05:03.698 
00:05:03.698 Runtime Environment - 
00:05:03.701    OS Version: Microsoft Windows NT 6.1.7601 Service Pack 1
00:05:03.701   CLR Version: 2.0.50727.5485 ( Net 3.5 )
00:05:03.701 
00:05:03.795 ProcessModel: Default    DomainUsage: Single
00:05:03.795 Execution Runtime: net-3.5
00:05:33.886 Unable to locate fixture 
00:05:33.895 Process 'nunit-console-x86' [PID 3684] has finished profiling.

It happens randomly. I do not change the test assembly or the NUnit configuration. I run NUnit via NCover, but the same problem repeats when I use NUnit alone from the command line.

After enabling the verbose logging in NUnit I noticed that the nunit-agent process prints out its first messages to the log more than half a minute after it was run by the nunit-console. I found out from the source code that nunit-console waits 30 seconds for the spawned nunit-agent process to register itself. Apparently something delays loading nunit-agent so the timeout is hit in nunit-console causing the "Unable to locate fixture ". The nunit-agent process is still running after that and I have to kill it manually.

NUnit-console log:

InternalTrace: Initializing at level Verbose
09:14:08.992 Info  [ 1] Runner: NUnit-console.exe starting
09:14:09.006 Debug [ 1] ServiceManager: Added SettingsService
09:14:09.006 Debug [ 1] ServiceManager: Added DomainManager
09:14:09.007 Debug [ 1] ServiceManager: Added ProjectService
09:14:09.007 Debug [ 1] ServiceManager: Added AddinRegistry
09:14:09.007 Debug [ 1] ServiceManager: Added AddinManager
09:14:09.007 Debug [ 1] ServiceManager: Added TestAgency
09:14:09.008 Info  [ 1] ServiceManager: Initializing SettingsService
09:14:09.008 Info  [ 1] ServiceManager: Initializing DomainManager
09:14:09.008 Info  [ 1] ServiceManager: Initializing ProjectService
09:14:09.008 Info  [ 1] ServiceManager: Initializing AddinRegistry
09:14:09.008 Info  [ 1] ServiceManager: Initializing AddinManager
09:14:09.009 Debug [ 1] ServiceManager: Request for service IAddinRegistry satisfied by AddinRegistry
09:14:09.017 Info  [ 1] ServiceManager: Initializing TestAgency
09:14:09.041 Debug [ 1] ServiceManager: Request for service ProjectService satisfied by ProjectService
09:14:09.054 Debug [ 1] RuntimeFrameworkSelector: Current framework is net-3.5
09:14:09.054 Debug [ 1] RuntimeFrameworkSelector: No specific framework requested
09:14:09.054 Debug [ 1] ServiceManager: Request for service ISettings satisfied by SettingsService
09:14:09.058 Debug [ 1] RuntimeFrameworkSelector: Assembly D:\Jenkins\jobs\Job1\GreyBoxTests\bin\Debug\GreyBoxTests.dll uses version 4.0.30319
09:14:09.064 Debug [ 1] ServiceManager: Request for service TestAgency satisfied by TestAgency
09:14:09.065 Debug [ 1] RuntimeFrameworkSelector: Test will use net-4.0 framework
09:14:09.066 Info  [ 1] ProcessRunner: Loading GreyBoxTests.dll
09:14:09.067 Info  [ 1] TestAgency: Getting agent for use under net-4.0
09:14:09.070 Debug [ 1] TestAgency: Using nunit-agent at c:\Program Files (x86)\NUnit 2.6.3\bin\nunit-agent-x86.exe
09:14:09.091 Info  [ 1] TestAgency: Launched Agent process 7240 - see nunit-agent_7240.log
09:14:09.091 Info  [ 1] TestAgency: Command line: "c:\Program Files (x86)\NUnit 2.6.3\bin\nunit-agent-x86.exe" 65bc321d-e7dc-4a98-81e6-919b87d5c783 tcp://127.0.0.1:56614/TestAgency
09:14:09.091 Debug [ 1] TestAgency: Waiting for agent {65bc321d-e7dc-4a98-81e6-919b87d5c783} to register
09:14:39.091 Info  [ 1] Runner: NUnit-console.exe terminating

NUnit-agent log:

InternalTrace: Initializing at level Verbose
09:14:41.859 Info  [ 1] NUnitTestAgent: Agent process 7240 starting
09:14:41.876 Info  [ 1] NUnitTestAgent: Running under version 4.0.30319.18444, Net 4.5
09:14:41.876 Info  [ 1] NUnitTestAgent: Adding Services
09:14:41.876 Debug [ 1] ServiceManager: Added SettingsService
09:14:41.877 Debug [ 1] ServiceManager: Added ProjectService
09:14:41.877 Debug [ 1] ServiceManager: Added DomainManager
09:14:41.877 Debug [ 1] ServiceManager: Added AddinRegistry
09:14:41.877 Debug [ 1] ServiceManager: Added AddinManager
09:14:41.877 Info  [ 1] NUnitTestAgent: Initializing Services
09:14:41.878 Info  [ 1] ServiceManager: Initializing SettingsService
09:14:41.878 Info  [ 1] ServiceManager: Initializing ProjectService
09:14:41.878 Info  [ 1] ServiceManager: Initializing DomainManager
09:14:41.878 Info  [ 1] ServiceManager: Initializing AddinRegistry
09:14:41.878 Info  [ 1] ServiceManager: Initializing AddinManager
09:14:41.879 Debug [ 1] ServiceManager: Request for service IAddinRegistry satisfied by AddinRegistry
09:14:41.906 Info  [ 1] NUnitTestAgent: Connecting to TestAgency at tcp://127.0.0.1:56614/TestAgency
09:14:41.907 Info  [ 1] NUnitTestAgent: Starting RemoteTestAgent
09:14:41.908 Info  [ 1] RemoteTestAgent: Agent starting

Any NUnit experts could help me with this?

Answer 1

Potential workaround, suggested by Charlie in that Google Groups thread:

One way to avoid this is to stop using the agent. Change the config file (nunit-console-x86.exe.config) to use the 4.0 CLR before the 2.0 CLR. Then the test will run in the same process and no agent will be created.

I have confirmed that adding <supportedRuntime version="v4.0.30319" /> inside <startup> in the nunit-console.exe.config file (or nunit-console-x86.exe.config), and removing <supportedRuntime version="v2.0.50727" (if present) does cause my tests to run without spawning an nunit-agent.exe process. I have not confirmed whether that fixes the error "unable to locate fixture" in my case, but the OP (krzysiek_w) did confirm it in the same thread:

I was not aware of the possibility to run tests in nunit-console without the nunit-agent. After setting the supported framework in the nunit-console config file, the tests execute without creating the separate process which completely fixes the problem.

As an additional note, the option /trace=Verbose can be passed to NUnit to get more info, as krzysiek_w did in that thread. For me, those logs are output to C:\Users\(myuser)\AppData\Local\NUnit\logs.