test: 添加 Utils 纯函数单元测试 (测试计划 02)

覆盖 xml, hash, stringUtils, semver, uuid, format, frontmatterParser,
file, glob, diff 共 10 个模块的纯函数测试。
json.ts 因模块加载链路过重暂跳过。
共 190 个测试用例（含已有 array/set）全部通过。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/utils/__tests__/diff.test.ts

@@ -0,0 +1,77 @@
+import { describe, expect, test } from "bun:test";
+import { adjustHunkLineNumbers, getPatchFromContents } from "../diff";
+
+describe("adjustHunkLineNumbers", () => {
+  test("shifts hunk line numbers by offset", () => {
+    const hunks = [
+      { oldStart: 1, oldLines: 3, newStart: 1, newLines: 4, lines: [" a", "-b", "+c", "+d", " e"] },
+    ] as any[];
+    const result = adjustHunkLineNumbers(hunks, 10);
+    expect(result[0].oldStart).toBe(11);
+    expect(result[0].newStart).toBe(11);
+  });
+
+  test("returns original hunks for zero offset", () => {
+    const hunks = [
+      { oldStart: 5, oldLines: 2, newStart: 5, newLines: 2, lines: [] },
+    ] as any[];
+    const result = adjustHunkLineNumbers(hunks, 0);
+    expect(result).toBe(hunks); // same reference
+  });
+
+  test("handles negative offset", () => {
+    const hunks = [
+      { oldStart: 10, oldLines: 2, newStart: 10, newLines: 2, lines: [] },
+    ] as any[];
+    const result = adjustHunkLineNumbers(hunks, -5);
+    expect(result[0].oldStart).toBe(5);
+    expect(result[0].newStart).toBe(5);
+  });
+
+  test("handles empty hunks array", () => {
+    expect(adjustHunkLineNumbers([], 10)).toEqual([]);
+  });
+});
+
+describe("getPatchFromContents", () => {
+  test("returns hunks for different content", () => {
+    const hunks = getPatchFromContents({
+      filePath: "test.txt",
+      oldContent: "hello\nworld",
+      newContent: "hello\nplanet",
+    });
+    expect(hunks.length).toBeGreaterThan(0);
+    expect(hunks[0].lines.some((l: string) => l.startsWith("-"))).toBe(true);
+    expect(hunks[0].lines.some((l: string) => l.startsWith("+"))).toBe(true);
+  });
+
+  test("returns empty hunks for identical content", () => {
+    const hunks = getPatchFromContents({
+      filePath: "test.txt",
+      oldContent: "same content",
+      newContent: "same content",
+    });
+    expect(hunks).toEqual([]);
+  });
+
+  test("handles content with ampersands", () => {
+    const hunks = getPatchFromContents({
+      filePath: "test.txt",
+      oldContent: "a & b",
+      newContent: "a & c",
+    });
+    expect(hunks.length).toBeGreaterThan(0);
+    // Verify ampersands are unescaped in the output
+    const allLines = hunks.flatMap((h: any) => h.lines);
+    expect(allLines.some((l: string) => l.includes("&"))).toBe(true);
+  });
+
+  test("handles empty old content (new file)", () => {
+    const hunks = getPatchFromContents({
+      filePath: "test.txt",
+      oldContent: "",
+      newContent: "new content",
+    });
+    expect(hunks.length).toBeGreaterThan(0);
+  });
+});