test: isolate package-manager dependent hooks and formatter tests

tests/hooks/hooks.test.js

@@ -1221,9 +1221,14 @@ async function runTests() {
       fs.writeFileSync(path.join(rootDir, '.prettierrc'), '{}');
       fs.writeFileSync(filePath, 'export const value = 1;\n');
       createCommandShim(binDir, 'npx', logFile);
+      const isolatedHome = path.join(testDir, 'isolated-home');
+      fs.mkdirSync(path.join(isolatedHome, '.claude'), { recursive: true });
 
       const stdinJson = JSON.stringify({ tool_input: { file_path: filePath } });
-      const result = await runScript(path.join(scriptsDir, 'post-edit-format.js'), stdinJson, withPrependedPath(binDir));
+      const result = await runScript(path.join(scriptsDir, 'post-edit-format.js'), stdinJson, withPrependedPath(binDir, {
+        HOME: isolatedHome,
+        USERPROFILE: isolatedHome
+      }));
 
       assert.strictEqual(result.code, 0, 'Should exit 0 for config-only repo');
       const logEntries = readCommandLog(logFile);

tests/lib/package-manager.test.js

@@ -37,6 +37,33 @@ function cleanupTestDir(testDir) {
   fs.rmSync(testDir, { recursive: true, force: true });
 }
 
+function withIsolatedHome(fn) {
+  const isolatedHome = fs.mkdtempSync(path.join(os.tmpdir(), 'pm-home-'));
+  const originalHome = process.env.HOME;
+  const originalUserProfile = process.env.USERPROFILE;
+
+  process.env.HOME = isolatedHome;
+  process.env.USERPROFILE = isolatedHome;
+
+  try {
+    return fn(isolatedHome);
+  } finally {
+    if (originalHome !== undefined) {
+      process.env.HOME = originalHome;
+    } else {
+      delete process.env.HOME;
+    }
+
+    if (originalUserProfile !== undefined) {
+      process.env.USERPROFILE = originalUserProfile;
+    } else {
+      delete process.env.USERPROFILE;
+    }
+
+    fs.rmSync(isolatedHome, { recursive: true, force: true });
+  }
+}
+
 // Test suite
 function runTests() {
   console.log('\n=== Testing package-manager.js ===\n');
@@ -711,9 +738,11 @@ function runTests() {
     const originalEnv = process.env.CLAUDE_PACKAGE_MANAGER;
     try {
       delete process.env.CLAUDE_PACKAGE_MANAGER;
-      const result = pm.getPackageManager({ projectDir: testDir });
+      withIsolatedHome(() => {
-      assert.strictEqual(result.name, 'npm', 'Should default to npm');
+        const result = pm.getPackageManager({ projectDir: testDir });
-      assert.strictEqual(result.source, 'default');
+        assert.strictEqual(result.name, 'npm', 'Should default to npm');
+        assert.strictEqual(result.source, 'default');
+      });
     } finally {
       if (originalEnv !== undefined) {
         process.env.CLAUDE_PACKAGE_MANAGER = originalEnv;

tests/lib/resolve-formatter.test.js

@@ -58,6 +58,33 @@ function cleanupTmpDirs() {
   tmpDirs.length = 0;
 }
 
+function withIsolatedHome(fn) {
+  const isolatedHome = fs.mkdtempSync(path.join(os.tmpdir(), 'resolve-fmt-home-'));
+  const originalHome = process.env.HOME;
+  const originalUserProfile = process.env.USERPROFILE;
+
+  process.env.HOME = isolatedHome;
+  process.env.USERPROFILE = isolatedHome;
+
+  try {
+    return fn(isolatedHome);
+  } finally {
+    if (originalHome !== undefined) {
+      process.env.HOME = originalHome;
+    } else {
+      delete process.env.HOME;
+    }
+
+    if (originalUserProfile !== undefined) {
+      process.env.USERPROFILE = originalUserProfile;
+    } else {
+      delete process.env.USERPROFILE;
+    }
+
+    fs.rmSync(isolatedHome, { recursive: true, force: true });
+  }
+}
+
 function runTests() {
   console.log('\n=== Testing resolve-formatter.js ===\n');
 
@@ -168,10 +195,12 @@ function runTests() {
 
   run('resolveFormatterBin: falls back to npx for biome', () => {
     const root = makeTmpDir();
-    const result = resolveFormatterBin(root, 'biome');
+    withIsolatedHome(() => {
-    const expectedBin = process.platform === 'win32' ? 'npx.cmd' : 'npx';
+      const result = resolveFormatterBin(root, 'biome');
-    assert.strictEqual(result.bin, expectedBin);
+      const expectedBin = process.platform === 'win32' ? 'npx.cmd' : 'npx';
-    assert.deepStrictEqual(result.prefix, ['@biomejs/biome']);
+      assert.strictEqual(result.bin, expectedBin);
+      assert.deepStrictEqual(result.prefix, ['@biomejs/biome']);
+    });
   });
 
   run('resolveFormatterBin: uses local prettier binary when available', () => {
@@ -188,10 +217,12 @@ function runTests() {
 
   run('resolveFormatterBin: falls back to npx for prettier', () => {
     const root = makeTmpDir();
-    const result = resolveFormatterBin(root, 'prettier');
+    withIsolatedHome(() => {
-    const expectedBin = process.platform === 'win32' ? 'npx.cmd' : 'npx';
+      const result = resolveFormatterBin(root, 'prettier');
-    assert.strictEqual(result.bin, expectedBin);
+      const expectedBin = process.platform === 'win32' ? 'npx.cmd' : 'npx';
-    assert.deepStrictEqual(result.prefix, ['prettier']);
+      assert.strictEqual(result.bin, expectedBin);
+      assert.deepStrictEqual(result.prefix, ['prettier']);
+    });
   });
 
   run('resolveFormatterBin: returns null for unknown formatter', () => {