test: add coverage for toRelativePath and getDirectoryForPath (#95)

These two exported functions in src/utils/path.ts lacked unit tests.

toRelativePath wraps Node's path.relative() and keeps the absolute
path when the result would start with '..' (i.e. the target is outside
the CWD). Four tests cover: child-of-cwd, outside-cwd, cwd-itself,
and the type-safety invariant.

getDirectoryForPath uses statSync to distinguish directories from files,
falling back to dirname() for non-existent paths and bypassing the
filesystem for UNC paths (NTLM credential-leak prevention). Three tests
cover: existing directory, known file, and non-existent path.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: JiayuuWang

src/utils/__tests__/path.test.ts

@@ -1,8 +1,11 @@
 import { describe, expect, test } from "bun:test";
+import { resolve } from "path";
 import {
   containsPathTraversal,
   expandPath,
   normalizePathForConfigKey,
+  toRelativePath,
+  getDirectoryForPath,
 } from "../path";
 
 // ─── containsPathTraversal ──────────────────────────────────────────────
@@ -129,3 +132,68 @@ describe("normalizePathForConfigKey", () => {
     expect(result).toBe("foo/bar");
   });
 });
+
+// ─── toRelativePath ─────────────────────────────────────────────────────
+
+describe("toRelativePath", () => {
+  test("returns relative path for a child of cwd", () => {
+    // Build a path that is inside the current working directory.
+    // resolve() returns an absolute path, and toRelativePath should give
+    // back just the final segment (or relative form without ..).
+    const abs = resolve(process.cwd(), "package.json");
+    const result = toRelativePath(abs);
+    expect(result).toBe("package.json");
+    expect(result).not.toContain("..");
+  });
+
+  test("returns absolute path when target is outside cwd", () => {
+    // A well-known absolute path that is always outside any typical cwd
+    // (any absolute path that doesn't start with process.cwd() will work)
+    const cwd = process.cwd();
+    // Build a path guaranteed to be outside cwd by going to the root's parent
+    // of cwd, then a sibling directory with an unlikely name
+    const outsidePath = resolve(cwd, "../../__unlikely_dir_xyz__");
+    const result = toRelativePath(outsidePath);
+    // relative(cwd, outsidePath) will start with '../..' so function returns absolute
+    expect(result).toBe(outsidePath);
+  });
+
+  test("returns empty string for cwd itself", () => {
+    const cwd = process.cwd();
+    const result = toRelativePath(cwd);
+    // relative(cwd, cwd) === '' which does not start with '..'
+    expect(result).toBe("");
+  });
+
+  test("returns a string for any absolute path", () => {
+    const abs = resolve(process.cwd(), "src");
+    const result = toRelativePath(abs);
+    expect(typeof result).toBe("string");
+  });
+});
+
+// ─── getDirectoryForPath ─────────────────────────────────────────────────
+
+describe("getDirectoryForPath", () => {
+  test("returns the path itself when given an existing directory", () => {
+    // The src directory is guaranteed to exist in this repo
+    const dir = resolve(process.cwd(), "src");
+    const result = getDirectoryForPath(dir);
+    expect(result).toBe(dir);
+  });
+
+  test("returns parent directory for a known file", () => {
+    // package.json is at the repo root
+    const file = resolve(process.cwd(), "package.json");
+    const expectedParent = process.cwd();
+    const result = getDirectoryForPath(file);
+    expect(result).toBe(expectedParent);
+  });
+
+  test("returns parent directory for a non-existent path", () => {
+    const nonExistent = resolve(process.cwd(), "does-not-exist-xyz123.ts");
+    const expectedParent = process.cwd();
+    const result = getDirectoryForPath(nonExistent);
+    expect(result).toBe(expectedParent);
+  });
+});