test: expand test coverage — only utils tested, server and client have zero tests

Problem

Test coverage is minimal. Only utils.py has tests. The two most critical modules — server.py (all tool functions) and client.py (API communication) — have zero test coverage.

Current test coverage

tests/
├── conftest.py      # 3 fixtures
└── test_utils.py    # 6 tests for utils.py only

Untested modules

Proposed solution

Priority 1: client.py tests

# tests/test_client.py
def test_client_auth_header():
    """Verify Authorization header is set correctly."""

def test_client_handles_api_error_codes():
    """Verify status_code != 0 raises appropriate exceptions."""

def test_client_handles_auth_error_1004():
    """Verify 1004 raises MinimaxAuthError."""

def test_client_handles_network_error():
    """Verify RequestException is wrapped in MinimaxRequestError."""

Priority 2: server.py tool tests (with mocked API)

# tests/test_tools.py
def test_text_to_audio_validates_empty_text():
    """Verify empty text raises MinimaxRequestError."""

def test_generate_video_validates_empty_prompt():
    """Verify empty prompt raises MinimaxRequestError."""

def test_text_to_image_validates_empty_prompt():
    """Verify empty prompt raises MinimaxRequestError."""

Use unittest.mock.patch to mock api_client calls.

Acceptance criteria

• client.py has tests for auth, error handling, and request methods
• Tool functions have tests for input validation and error paths
• Coverage target: >60% for client.py, >40% for server.py

Start with tests/conftest.py and tests/test_utils.py to understand the existing fixtures and style, then inspect client.py and server.py. Add tests/test_client.py for authentication, API and network errors, and tests/test_tools.py for empty-input validation using unittest.mock.patch for api_client calls. Done means the stated client.py and server.py coverage targets and acceptance criteria are met.