🔑 Write Unit & Integration Tests for Authentication Flow

[sensasi-delight]

The authentication system supports email/password and OAuth (Google & GitHub).
We need comprehensive unit and integration tests to ensure reliability, security, and a smooth user experience.

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✅ Tasks

• Unit Tests

  • Test validation rules for email and password.
  • Test username auto-generation (for OAuth users).
  • Test error handling for invalid credentials.
  • Test password hashing & comparison logic.
  • Test token/session creation and expiration logic.

• Integration Tests

  • Test end-to-end signup (email/password).
  • Test login flow (email/password).
  • Test OAuth login via Google.
  • Test OAuth login via GitHub.
  • Test logout flow and session invalidation.
  • Test protected routes access (authenticated vs unauthenticated).
  • Test error cases: duplicate email, invalid token, expired session.

• Infrastructure

  • Setup test database (isolated from production).
  • Use mocks/stubs for external OAuth providers where needed.
  • Add CI workflow to run tests automatically on PR.

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🎯 Acceptance Criteria

• All core authentication paths (signup, login, logout, OAuth) are covered by tests.
• Tests pass reliably in CI/CD environment.
• Coverage for authentication module ≥ 80%.