fix: UT error

--bug=1

Author: studyzy

Makefile

@@ -37,4 +37,7 @@ release:
 	$(PNPM) run release:local
 
 test:
-	$(PNPM) test
+	$(PNPM) test
+
+lint:
+	$(PNPM) lint

test/core/completions/installers/zsh-installer.test.ts

@@ -8,15 +8,27 @@ import { ZshInstaller } from '../../../../src/core/completions/installers/zsh-in
 describe('ZshInstaller', () => {
   let testHomeDir: string;
   let installer: ZshInstaller;
+  let originalZshEnv: string | undefined;
 
   beforeEach(async () => {
+    // Save and clear ZSH environment variable to avoid interference with tests
+    originalZshEnv = process.env.ZSH;
+    delete process.env.ZSH;
+
     // Create a temporary home directory for testing
     testHomeDir = path.join(os.tmpdir(), `openspec-zsh-test-${randomUUID()}`);
     await fs.mkdir(testHomeDir, { recursive: true });
     installer = new ZshInstaller(testHomeDir);
   });
 
   afterEach(async () => {
+    // Restore ZSH environment variable
+    if (originalZshEnv !== undefined) {
+      process.env.ZSH = originalZshEnv;
+    } else {
+      delete process.env.ZSH;
+    }
+
     // Clean up test directory
     await fs.rm(testHomeDir, { recursive: true, force: true });
   });