Test Runner exceptions when the GUI does not.

[bazzboyy1]

There seems to be anm issue with the UnityMCP - run_tests (MCP)(mode: "play") command.

Basically if I try have claude code run the test runner, the test runner throws exceptions. When I run the tests manually via the GUI, it works fine.

It's pretty important that this works for iteration purposes.

I sincerely apologise for this horrendous console dump:

UnityMCP - read_console (MCP)(action: "get", count: 50, format: "detailed")
⎿ {
"success": true,
"message": "Retrieved 9 log entries.",
"data": [
{
"type": "Log",
"message": "<color=#2EA3FF>MCP-FOR-UNITY: MCPForUnityBridge started on port 6400.
(OS=WindowsEditor, server=6.3.0)",
"file": "./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/McpLog.cs",
"line": 20,
"stackTrace": "UnityEngine.Debug:Log (object)\nMCPForUnity.Editor.Helpers.McpLog:Info (string,bool) (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/McpLog.cs:20)\nMCPForUnity.Editor.MC
PForUnityBridge:Start () (at ./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/MCPForUnityBrid
ge.cs:395)\nMCPForUnity.Editor.MCPForUnityBridge:EnsureStartedOnEditorIdle () (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/MCPForUnityBridge.cs:267)\nUnityEditor.Edito
rApplication:Internal_CallUpdateFunctions ()"
},
{
"type": "Log",
"message": "<color=#2EA3FF>MCP-FOR-UNITY: Auto-discovered 10 tools and 3 resources (13
total handlers)",
"file": "./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/McpLog.cs",
"line": 20,
"stackTrace": "UnityEngine.Debug:Log (object)\nMCPForUnity.Editor.Helpers.McpLog:Info (string,bool) (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/McpLog.cs:20)\nMCPForUnity.Editor.To
ols.CommandRegistry:AutoDiscoverCommands () (at ./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Edi
tor/Tools/CommandRegistry.cs:101)\nMCPForUnity.Editor.Tools.CommandRegistry:Initialize () (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Tools/CommandRegistry.cs:50)\nMCPForUnity.Ed
itor.MCPForUnityBridge:Start () (at ./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/MCPForUn
ityBridge.cs:399)\nMCPForUnity.Editor.MCPForUnityBridge:EnsureStartedOnEditorIdle () (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/MCPForUnityBridge.cs:267)\nUnityEditor.Edito
rApplication:Internal_CallUpdateFunctions ()"
},
{
"type": "Log",
"message": "<color=#2EA3FF>MCP-FOR-UNITY: No PythonToolsAsset found. Create one via Assets
> Create > MCP For Unity > Python Tools",
"file": "./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/McpLog.cs",
"line": 20,
"stackTrace": "UnityEngine.Debug:Log (object)\nMCPForUnity.Editor.Helpers.McpLog:Info (string,bool) (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/McpLog.cs:20)\nMCPForUnity.Editor.Se
rvices.ToolSyncService:SyncProjectTools (string) (at ./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038b
e/Editor/Services/ToolSyncService.cs:32)\nMCPForUnity.Editor.Helpers.PythonToolSyncProcessor:SyncAllTools ()
(at ./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/PythonToolSyncProcessor.cs:96)\n
MCPForUnity.Editor.Helpers.PythonToolSyncProcessor/<>c:<.cctor>b__2_0 () (at
./Library/PackageCache/com.coplaydev.unity-mcp@2ab49ec038be/Editor/Helpers/PythonToolSyncProcessor.cs:29)\nUnit
yEditor.EditorApplication:Internal_CallDelayFunctions ()"
},
{
"type": "Exception",
"message": "InvalidOperationException: This cannot be used during play mode.",
"file": "./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/Task
s/Scene/SaveModifiedSceneTask.cs",
"line": 13,
"stackTrace": "UnityEditor.SceneManagement.EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo
(System.String message) (at <08b6666d108d4c9796450fb85df4d5b2>:0)\nUnityEditor.SceneManagement.EditorSceneManag
er.SaveCurrentModifiedScenesIfUserWantsTo () (at <08b6666d108d4c9796450fb85df4d5b2>:0)\nUnityEditor.TestTools.T
estRunner.TestRun.Tasks.Scene.SaveModifiedSceneTask+d__1.MoveNext () (at
./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/Tasks/Scene/SaveMod
ifiedSceneTask.cs:13)\nUnityEditor.TestTools.TestRunner.TestRun.TestJobRunner.ExecuteStep () (at
./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/TestJobRunner.cs:17
3)\nUnityEditor.EditorApplication:Internal_CallUpdateFunctions()"
},
{
"type": "Log",
"message": "An unexpected error happened while running tests.",
"file": "./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/Api/Callback
sDelegator.cs",
"line": 67,
"stackTrace": "UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()"
},
{
"type": "Log",
"message": "Too many instant steps in test execution mode: Error. Current task ExitPlayModeTask.",
"file":
"./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/TestJobRunner.cs",
"line": 119,
"stackTrace": "UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()"
},
{
"type": "Exception",
"message": "Exception: Playmode tests were aborted because the player was stopped.",
"file": "./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/Task
s/PlayModeRunTask.cs",
"line": 59,
"stackTrace": "UnityEditor.TestTools.TestRunner.TestRun.Tasks.PlayModeRunTask+d__1.MoveNext ()
(at ./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/Tasks/PlayModeR
unTask.cs:59)\nUnityEditor.TestTools.TestRunner.TestRun.TestJobRunner.ExecuteStep () (at
./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/TestJobRunner.cs:17
3)\nUnityEditor.EditorApplication:Internal_CallUpdateFunctions()"
},
{
"type": "Log",
"message": "An unexpected error happened while running tests.",
"file": "./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/Api/Callback
sDelegator.cs",
"line": 67,
"stackTrace": "UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()"
},
{
"type": "Warning",
"message": "Executing IPostBuildCleanup for: Unity.PerformanceTesting.Editor.TestRunBuilder.",
"file": "./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/Task
s/BuildActionTaskBase.cs",
"line": 51,
"stackTrace": "UnityEditor.EditorApplication:Internal_CallUpdateFunctions ()"
}
]
}

[coderabbitai]

A summary of the changes CodeRabbit can apply:

• Update MCPForUnity/Editor/Services/TestRunnerService.cs to set ExecutionSettings.runSynchronously = true when mode == TestMode.PlayMode so PlayMode tests run synchronously, preventing the SaveModifiedSceneTask InvalidOperationException and leaving EditMode behavior unchanged.

• Update MCPForUnity/Editor/Services/TestRunnerService.cs to replace the direct _testRunnerApi.Execute(...) call with a new ExecutionSettings instance (including a comment/link) and set settings.runSynchronously = true when mode == TestMode.PlayMode before calling _testRunnerApi.Execute(settings) to prevent scene save conflicts during PlayMode test runs.

• ✅ Create PR with these edits
• 📋 Get copyable edits

[msanatan]

@bazzboyy1 you can use markdown tags to help format the dump, like ``` (https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax)

Thanks for flagging! With the test runner I've mostly used it for editor mode tests, less so for Play mode. It looks like our AI helper might has some ideas but I'm not sure that's the actual fix.

Why do you have SaveModifiedSceneTask.cs? That file is calling SaveCurrentModifiedScenesIfUserWantsTo(), which is not available in Play mode. It's an error with your code and setup.

Instead of using that file, you can save the scene manually or instruct the LLM to do so before running tests

[msanatan]

@bazzboyy1 let me know, I'll close by Monday. Logs indicate it's an error in your project

[bazzboyy1]

Hey so I'm not calling this from my code, it's from the Unity Test Runner. It's the one trying to save the scene. I've tried running this in an empty scene and I get the same result.

InvalidOperationException: This cannot be used during play mode. UnityEditor.SceneManagement.EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo (System.String message) (at <08b6666d108d4c9796450fb85df4d5b2>:0) UnityEditor.SceneManagement.EditorSceneManager.SaveCurrentModifiedScenesIfUserWantsTo () (at <08b6666d108d4c9796450fb85df4d5b2>:0) UnityEditor.TestTools.TestRunner.TestRun.Tasks.Scene.SaveModifiedSceneTask+<Execute>d__1.MoveNext () (at ./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/Tasks/Scene/SaveModifiedSceneTask.cs:13) UnityEditor.TestTools.TestRunner.TestRun.TestJobRunner.ExecuteStep () (at ./Library/PackageCache/com.unity.test-framework@5ac417e07314/UnityEditor.TestRunner/TestRun/TestJobRunner.cs:173) UnityEditor.EditorApplication:Internal_CallUpdateFunctions()

Could this be a bug with the Unity API? I'm running Unity V6.0.4