Storage Service: Fetch updates on any group record merge

ts/test-both/util/diffArraysAsSets_test.ts

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+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { diffArraysAsSets } from '../../util/diffArraysAsSets';
+
+function assertMatch<T>({
+  added,
+  removed,
+}: {
+  added: Array<T>;
+  removed: Array<T>;
+}) {
+  return added.length === 0 && removed.length === 0;
+}
+
+describe('diffArraysAsSets', () => {
+  it('returns true if arrays are both empty', () => {
+    const left: Array<string> = [];
+    const right: Array<string> = [];
+
+    assertMatch(diffArraysAsSets(left, right));
+  });
+
+  it('returns true if arrays are equal', () => {
+    const left = [1, 2, 3];
+    const right = [1, 2, 3];
+
+    assertMatch(diffArraysAsSets(left, right));
+  });
+
+  it('returns true if arrays are equal but out of order', () => {
+    const left = [1, 2, 3];
+    const right = [3, 1, 2];
+
+    assertMatch(diffArraysAsSets(left, right));
+  });
+
+  it('returns true if arrays are equal but one has duplicates', () => {
+    const left = [1, 2, 3, 1];
+    const right = [1, 2, 3];
+
+    assertMatch(diffArraysAsSets(left, right));
+  });
+
+  it('returns false if first array has missing elements', () => {
+    const left = [1, 2];
+    const right = [1, 2, 3];
+
+    const { added, removed } = diffArraysAsSets(left, right);
+    assert.deepEqual(added, [3]);
+    assert.deepEqual(removed, []);
+  });
+
+  it('returns false if second array has missing elements', () => {
+    const left = [1, 2, 3];
+    const right = [1, 2];
+
+    const { added, removed } = diffArraysAsSets(left, right);
+    assert.deepEqual(added, []);
+    assert.deepEqual(removed, [3]);
+  });
+
+  it('returns false if second array is empty', () => {
+    const left = [1, 2, 3];
+    const right: Array<number> = [];
+
+    const { added, removed } = diffArraysAsSets(left, right);
+    assert.deepEqual(added, []);
+    assert.deepEqual(removed, [1, 2, 3]);
+  });
+});