diff --git a/test/sets-test.ts b/test/sets-test.ts
new file mode 100644
index 0000000000..e884d0e9af
--- /dev/null
+++ b/test/sets-test.ts
@@ -0,0 +1,56 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import {setHasDiff} from "../src/utils/sets";
+
+describe('sets', () => {
+    describe('setHasDiff', () => {
+        it('should flag true on A length > B length', () => {
+            const a = new Set([1, 2, 3, 4]);
+            const b = new Set([1, 2, 3]);
+            const result = setHasDiff(a, b);
+            expect(result).toBe(true);
+        });
+
+        it('should flag true on A length < B length', () => {
+            const a = new Set([1, 2, 3]);
+            const b = new Set([1, 2, 3, 4]);
+            const result = setHasDiff(a, b);
+            expect(result).toBe(true);
+        });
+
+        it('should flag true on element differences', () => {
+            const a = new Set([1, 2, 3]);
+            const b = new Set([4, 5, 6]);
+            const result = setHasDiff(a, b);
+            expect(result).toBe(true);
+        });
+
+        it('should flag false if same but order different', () => {
+            const a = new Set([1, 2, 3]);
+            const b = new Set([3, 1, 2]);
+            const result = setHasDiff(a, b);
+            expect(result).toBe(false);
+        });
+
+        it('should flag false if same', () => {
+            const a = new Set([1, 2, 3]);
+            const b = new Set([1, 2, 3]);
+            const result = setHasDiff(a, b);
+            expect(result).toBe(false);
+        });
+    });
+});