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ts/test-node/util/unicodeSlice_test.ts

@@ -0,0 +1,39 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import assert from 'node:assert/strict';
+import { unicodeSlice } from '../../util/unicodeSlice';
+import { byteLength } from '../../Bytes';
+
+describe('unicodeSlice()', () => {
+  function test(
+    title: string,
+    input: string,
+    begin: number,
+    end: number,
+    expected: string,
+    expectedSize: number
+  ): void {
+    it(title, () => {
+      const result = unicodeSlice(input, begin, end);
+      assert.strictEqual(result, expected);
+      assert.strictEqual(byteLength(result), expectedSize);
+    });
+  }
+
+  test('one-byte chars', '123456', 2, 4, '34', 2);
+  test('past max length', '123456', 0, 100, '123456', 6);
+  test('end before start', '123456', 5, 1, '', 0);
+  test('negative start', '123456', -5, 4, '1234', 4);
+  test('negative end', '123456', 0, -5, '', 0);
+  test('end at start', '123456', 3, 3, '', 0);
+
+  test('multi-byte char', 'x€x', 1, 4, '€', 3);
+  test('multi-byte char slice before end', '€', 1, 3, '', 0);
+  test('multi-byte char slice after start', '€', 2, 4, '', 0);
+
+  test('emoji', 'x👩‍👩‍👧‍👦x', 1, 26, '👩‍👩‍👧‍👦', 25);
+  test('emoji slice before end', 'x👩‍👩‍👧‍👦x', 1, 25, '', 0);
+  test('emoji slice after start', 'x👩‍👩‍👧‍👦x', 2, 26, '', 0);
+  test('emoji slice capture around', 'x👩‍👩‍👧‍👦x', 0, 27, 'x👩‍👩‍👧‍👦x', 27);
+});