1 files changed, 54 insertions, 0 deletions
diff --git a/src/lib/constants.test.ts b/src/lib/constants.test.ts
new file mode 100644
index 0000000..65fb466
--- /dev/null
+++ b/src/lib/constants.test.ts
@@ -0,0 +1,54 @@
+import { afterAll, beforeEach, describe, expect, test, vi } from 'vitest';
+
+const originalEnv = process.env;
+
+function setEnv(key: string, value?: string) {
+  if (value === undefined) {
+    delete process.env[key];
+    return;
+  }
+
+  process.env[key] = value;
+}
+
+describe('constants', () => {
+  beforeEach(() => {
+    vi.resetModules();
+    process.env = { ...originalEnv };
+  });
+
+  afterAll(() => {
+    process.env = originalEnv;
+  });
+
+  test('uses localhost base url outside production', async () => {
+    setEnv('NODE_ENV', 'development');
+    setEnv('VERCEL_PROJECT_PRODUCTION_URL', 'example.com');
+
+    const constants = await import('./constants');
+
+    expect(constants.isProduction).toBe(false);
+    expect(constants.baseUrl.href).toBe('http://localhost:3000/');
+  });
+
+  test('uses vercel production url in production', async () => {
+    setEnv('NODE_ENV', 'production');
+    setEnv('VERCEL_PROJECT_PRODUCTION_URL', 'blog.example.com');
+
+    const constants = await import('./constants');
+
+    expect(constants.isProduction).toBe(true);
+    expect(constants.baseUrl.href).toBe('https://blog.example.com/');
+  });
+
+  test('falls back to localhost when production url is missing', async () => {
+    setEnv('NODE_ENV', 'production');
+    setEnv('VERCEL_PROJECT_PRODUCTION_URL');
+
+    const constants = await import('./constants');
+
+    expect(constants.isProduction).toBe(true);
+    expect(constants.baseUrl.href).toBe('http://localhost:3000/');
+  });
+});
+