Add iterable utility tests

Unsurprisingly, it's a copy/paste of the array tests

test/iterables-test.ts

@@ -0,0 +1,77 @@
+/*
+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 {iterableDiff, iterableUnion} from "../src/utils/iterables";
+
+describe('iterables', () => {
+    describe('iterableUnion', () => {
+        it('should return a union', () => {
+            const a = [1, 2, 3];
+            const b = [1, 2, 4]; // note diff
+            const result = iterableUnion(a, b);
+            expect(result).toBeDefined();
+            expect(result).toHaveLength(2);
+            expect(result).toEqual([1, 2]);
+        });
+
+        it('should return an empty array on no matches', () => {
+            const a = [1, 2, 3];
+            const b = [4, 5, 6];
+            const result = iterableUnion(a, b);
+            expect(result).toBeDefined();
+            expect(result).toHaveLength(0);
+        });
+    });
+
+    describe('iterableDiff', () => {
+        it('should see added from A->B', () => {
+            const a = [1, 2, 3];
+            const b = [1, 2, 3, 4];
+            const result = iterableDiff(a, b);
+            expect(result).toBeDefined();
+            expect(result.added).toBeDefined();
+            expect(result.removed).toBeDefined();
+            expect(result.added).toHaveLength(1);
+            expect(result.removed).toHaveLength(0);
+            expect(result.added).toEqual([4]);
+        });
+
+        it('should see removed from A->B', () => {
+            const a = [1, 2, 3];
+            const b = [1, 2];
+            const result = iterableDiff(a, b);
+            expect(result).toBeDefined();
+            expect(result.added).toBeDefined();
+            expect(result.removed).toBeDefined();
+            expect(result.added).toHaveLength(0);
+            expect(result.removed).toHaveLength(1);
+            expect(result.removed).toEqual([3]);
+        });
+
+        it('should see added and removed in the same set', () => {
+            const a = [1, 2, 3];
+            const b = [1, 2, 4]; // note diff
+            const result = iterableDiff(a, b);
+            expect(result).toBeDefined();
+            expect(result.added).toBeDefined();
+            expect(result.removed).toBeDefined();
+            expect(result.added).toHaveLength(1);
+            expect(result.removed).toHaveLength(1);
+            expect(result.added).toEqual([4]);
+            expect(result.removed).toEqual([3]);
+        });
+    });
+});