Make playmode tests available only in editor and standalone.

Assets/Tests/NavMeshSurfaceAgentTests.cs

+#if UNITY_EDITOR || UNITY_STANDALONE
 using UnityEngine;
 using UnityEngine.AI;
 using UnityEngine.TestTools;
@@ -98,3 +99,4 @@ public IEnumerator AgentDoesNotAlignToSurfaceNextFrame()
         GameObject.DestroyImmediate(surface.gameObject);
     }
 }
+#endif

Assets/Tests/NavMeshSurfaceLinkTests.cs

+#if UNITY_EDITOR || UNITY_STANDALONE
 using UnityEngine;
 using UnityEngine.AI;
 using UnityEngine.TestTools;
@@ -141,3 +142,4 @@ public static bool HasPathConnectingViaPoint(GameObject a, GameObject b, Vector3
         return false;
     }
 }
+#endif

Assets/Tests/NavMeshSurfaceModifierTests.cs

+#if UNITY_EDITOR || UNITY_STANDALONE
 using UnityEngine;
 using UnityEngine.AI;
 using UnityEngine.TestTools;
@@ -108,3 +109,4 @@ public void ModifierOverrideAreaDoesNotAffectSibling()
         GameObject.DestroyImmediate(siblingPlane);
     }
 }
+#endif

Assets/Tests/NavMeshSurfaceModifierVolumeTests.cs

+#if UNITY_EDITOR || UNITY_STANDALONE
 using UnityEngine;
 using UnityEngine.AI;
 using UnityEngine.TestTools;
@@ -67,3 +68,4 @@ public void BuildUsesOnlyIncludedModifierVolume()
         Assert.IsTrue(NavMeshSurfaceTests.HasNavMeshAtOrigin(expectedAreaMask));
     }
 }
+#endif

Assets/Tests/NavMeshSurfaceTests.cs

+#if UNITY_EDITOR || UNITY_STANDALONE
 using UnityEngine;
 using UnityEngine.AI;
 using UnityEngine.TestTools;
@@ -198,3 +199,4 @@ public static bool HasNavMeshAtOrigin(int areaMask = NavMesh.AllAreas, int agent
         return NavMesh.SamplePosition(Vector3.zero, out hit, 0.1f, filter);
     }
 }
+#endif