Add reproducing tests environment

Reproducing steps:
1. Stay keep is not playing
2. Open the scene "Error"
3. Open an inspector for "AutopilotSettingsForFacingImmediatelyError"
4. Click Run

Expected Behaviour:
Stop playing and report the error to Slack

Actual Behaviour:
Still playing and did not report to Slack

Tests/Runtime/TestDoubles/StubClickAgent.cs

@@ -0,0 +1,39 @@
+// Copyright (c) 2023 DeNA Co., Ltd.
+// This software is released under the MIT License.
+
+using System.Threading;
+using Cysharp.Threading.Tasks;
+using DeNA.Anjin.Agents;
+using UnityEngine;
+using UnityEngine.EventSystems;
+
+namespace DeNA.Anjin.TestDoubles
+{
+    public class StubClickAgent : AbstractAgent
+    {
+        [SerializeField] public string targetName;
+
+        public override UniTask Run(CancellationToken token)
+        {
+            foreach (var obj in FindObjectsByType<GameObject>(FindObjectsSortMode.None))
+            {
+                if (obj.name != targetName)
+                {
+                    continue;
+                }
+
+                var target = obj;
+                if (!target.TryGetComponent<IPointerClickHandler>(out var handler))
+                {
+                    Debug.LogWarning(
+                        $"{target.name} did not have any components that derived {nameof(IPointerClickHandler)}"
+                    );
+                    continue;
+                }
+
+                handler.OnPointerClick(new PointerEventData(EventSystem.current));
+            }
+            return UniTask.CompletedTask;
+        }
+    }
+}

Tests/Runtime/TestDoubles/StubThrowingErrorOnClick.cs

@@ -0,0 +1,22 @@
+// Copyright (c) 2023 DeNA Co., Ltd.
+// This software is released under the MIT License.
+
+using System;
+using System.Threading;
+using UnityEngine;
+using UnityEngine.EventSystems;
+
+namespace DeNA.Anjin.TestDoubles
+{
+    /// <summary>
+    /// A test stub throw errors when clicked
+    /// </summary>
+    [AddComponentMenu("")]
+    public class StubThrowingErrorOnClick : MonoBehaviour, IPointerClickHandler
+    {
+        public void OnPointerClick(PointerEventData eventData)
+        {
+            throw new Exception($"TEST on thread #{Thread.CurrentThread.ManagedThreadId}");
+        }
+    }
+}

Tests/TestAssets/AutopilotSettingsForFacingImmediatelyError.asset

@@ -0,0 +1,33 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!114 &11400000
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: c7a1731caa574ed4b9334b7d52febe27, type: 3}
+  m_Name: AutopilotSettingsForFacingImmediatelyError
+  m_EditorClassIdentifier: 
+  description: 
+  sceneAgentMaps:
+  - scenePath: Packages/com.dena.anjin/Tests/TestScenes/Error.unity
+    agent: {fileID: 11400000, guid: 9a5c6d18335194c1b9f8e162695d73fd, type: 2}
+  fallbackAgent: {fileID: 0}
+  observerAgent: {fileID: 0}
+  lifespanSec: 0
+  randomSeed: 
+  timeScale: 1
+  junitReportPath: 
+  slackToken: 
+  slackChannels: 
+  mentionSubTeamIDs: 
+  addHereInSlackMessage: 0
+  handleException: 1
+  handleError: 1
+  handleAssert: 1
+  handleWarning: 0
+  ignoreMessages: []

Tests/TestAssets/StubClickAgentForTests.asset

@@ -0,0 +1,16 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!114 &11400000
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: fcc96872a9564f89be6b16a814ad0034, type: 3}
+  m_Name: StubClickAgentForTests
+  m_EditorClassIdentifier: 
+  description: 
+  targetName: ThrowErrorFromMainThreadOnClick

Tests/TestAssets/StubImmediatelyErrorAgentForTests.asset

@@ -0,0 +1,15 @@
+%YAML 1.1
+%TAG !u! tag:unity3d.com,2011:
+--- !u!114 &11400000
+MonoBehaviour:
+  m_ObjectHideFlags: 0
+  m_CorrespondingSourceObject: {fileID: 0}
+  m_PrefabInstance: {fileID: 0}
+  m_PrefabAsset: {fileID: 0}
+  m_GameObject: {fileID: 0}
+  m_Enabled: 1
+  m_EditorHideFlags: 0
+  m_Script: {fileID: 11500000, guid: bc82cbd7e5b6404da291e090ed1f4eba, type: 3}
+  m_Name: StubImmediatelyErrorAgentForTests
+  m_EditorClassIdentifier: 
+  description: