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+# Testing
+
+This document describes how to run and write tests for Bookhoard.
+
+## Test Users and Email Domains
+
+### Test Email Domain
+
+All integration tests use the email domain **`@tests.bookhoard.internal`** for test users. This domain is reserved exclusively for testing and will never be used in production.
+
+**Why this domain?**
+- Clear indication it's for testing only
+- Won't conflict with real user emails (which use real domains like `@gmail.com`, `@example.com`, etc.)
+- Safe cleanup: Tests can delete all users with this domain without risk to production data
+- If a real user somehow uses `@tests.bookhoard.internal`, they are explicitly opting into test data deletion
+
+### Standard Test Users
+
+The test suite creates these standard users:
+
+1. **Admin User**
+   - Email: `testuser@tests.bookhoard.internal`
+   - Username: `testuser`
+   - Password: `Test@Pass123!`
+   - Role: `admin`
+
+2. **Regular User**
+   - Email: `testregularuser@tests.bookhoard.internal`
+   - Username: `testregularuser`
+   - Password: `Test@Pass123!`
+   - Role: `user`
+
+### Test Lifecycle and Cleanup
+
+Each test run:
+1. **Deletes** all existing users with `@tests.bookhoard.internal` email
+2. **Creates** fresh standard test users
+3. **Runs** the test with clean state
+4. **Cleans up** via `t.Cleanup()` to delete users created during the test
+
+This ensures complete test isolation - no state leaks between tests.
+
+### Writing Tests
+
+When writing new tests:
+
+**✅ DO:**
+- Use the standard test users from `setupTestServer(t)`
+- Use `createRegularUserOnce(t, setup.DB)` for additional test users
+- Let the test framework handle cleanup
+- Use the `@tests.bookhoard.internal` domain if creating custom test users
+
+**❌ DON'T:**
+- Use real email domains like `@example.com` or `@gmail.com`
+- Manually manage test user deletion (unless absolutely necessary)
+- Assume test users persist between test runs
+- Hardcode user IDs (always look up by email/username)
+
+## Running Tests
+
+### Run All Tests
+```bash
+make test
+```
+
+### Run Integration Tests Only
+```bash
+make test-integration
+```
+
+### Run Specific Test
+```bash
+go test -v -run TestUpdateProfile ./cmd/server/tests/
+```
+
+### Run with Race Detection
+```bash
+go test -race ./cmd/server/tests/
+```
+
+## Test Organization
+
+Tests are located in `cmd/server/tests/`:
+
+- `test_helpers.go` - Test utilities and setup functions
+- `*_test.go` - Test files organized by feature
+  - `user_test.go` - User management tests
+  - `auth_test.go` - Authentication tests
+  - `media_test.go` - Media item tests
+  - etc.
+
+### Key Test Helpers
+
+- `setupTestServer(t *testing.T)` - Creates test server with clean DB state
+- `createTestUserOnce(t, db)` - Gets/creates standard admin user
+- `createRegularUserOnce(t, db)` - Gets/creates additional test users
+- `loginWithCredentials(t, server, email, password)` - Returns auth token
+
+## Bruno API Tests
+
+API integration tests in `bruno/` also use the test email domain:
+
+- Login test: `testuser@tests.bookhoard.internal`
+- Register test: `testuser@tests.bookhoard.internal`
+- Profile update test: `updated@tests.bookhoard.internal`
+
+See: [Bruno Documentation](https://docs.usebruno.com/)