Reorganize test cases

ts/test-node/util/isSorted_test.ts

@@ -0,0 +1,26 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+
+import { isSorted } from '../../util/isSorted';
+
+describe('isSorted', () => {
+  it('returns true for empty lists', () => {
+    assert.isTrue(isSorted([]));
+  });
+
+  it('returns true for one-element lists', () => {
+    assert.isTrue(isSorted([5]));
+  });
+
+  it('returns true for sorted lists', () => {
+    assert.isTrue(isSorted([1, 2]));
+    assert.isTrue(isSorted([1, 2, 2, 3]));
+  });
+
+  it('returns false for out-of-order lists', () => {
+    assert.isFalse(isSorted([2, 1]));
+    assert.isFalse(isSorted([1, 2, 2, 3, 0]));
+  });
+});