Test added to highlight the fixed bug

com.unity.perception/Tests/Runtime/GroundTruthTests/LabelEntryMatchCacheTests.cs

 using System.Collections;
 using NUnit.Framework;
+using Unity.Entities;
 using UnityEngine;
 using UnityEngine.Perception.GroundTruth;
 using UnityEngine.TestTools;
                 //allow label to be registered
                 yield return null;
                 Assert.IsFalse(cache.TryGetLabelEntryFromInstanceId(labeledPlane.GetComponent<Labeling>().instanceId, out var labelEntry, out var index));
+                Assert.AreEqual(-1, index);
+                Assert.AreEqual(default(IdLabelEntry), labelEntry);
+            }
+        }
+
+        [UnityTest]
+        public IEnumerator TryGet_ReturnsFalse_ForNonMatchingLabel_WhenAllObjectsAreDestroyedAndNewOnesAreCreated()
+        {
+            //only way to guarantee registration order is to run frames.
+
+            var labeledPlane = TestHelper.CreateLabeledPlane(label: "foo");
+
+            var config = ScriptableObject.CreateInstance<IdLabelConfig>();
+            config.Init(new[]
+            {
+                new IdLabelEntry()
+                {
+                    id = 1,
+                    label = "foo"
+                },
+            });
+
+            using (var cache = new LabelEntryMatchCache(config))
+            {
+                //allow label to be registered
+                yield return null;
+
+                //delete all labeled objects and run a frame so that instance ids of labeled entities reset
+                DestroyTestObject(labeledPlane);
+
+                yield return null;
+
+                var labeledPlane2 = TestHelper.CreateLabeledPlane(label: "bar");
+                AddTestObjectForCleanup(labeledPlane2);
+
+                //let labeledPlane2 be assigned a recycled instance id (1) previously belonging to labeledPlane
+                yield return null;
+
+                Assert.IsFalse(cache.TryGetLabelEntryFromInstanceId(labeledPlane2.GetComponent<Labeling>().instanceId, out var labelEntry, out var index));
                 Assert.AreEqual(-1, index);
                 Assert.AreEqual(default(IdLabelEntry), labelEntry);
             }