Add comprehensive unit test suite

- Add 111 unit tests covering all client classes and exceptions
- Test BaseClientMixin: initialization, validation, retry logic
- Test FastGPTClient: HTTP requests, streaming, error handling, context manager
- Test ChatClient: all chat operations (completion, histories, records, feedback)
- Test AppClient: app analytics and logs
- Test all exception classes with various configurations
- Add shared pytest fixtures in conftest.py

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,168 @@
+"""Pytest configuration and fixtures for FastGPT client tests."""
+
+import pytest
+from unittest.mock import Mock, MagicMock
+import httpx
+
+
+@pytest.fixture
+def api_key():
+    """Test API key."""
+    return "fastgpt-test-key-12345"
+
+
+@pytest.fixture
+def base_url():
+    """Test base URL."""
+    return "http://localhost:3000"
+
+
+@pytest.fixture
+def mock_response():
+    """Create a mock httpx.Response object."""
+    response = Mock(spec=httpx.Response)
+    response.status_code = 200
+    response.headers = {}
+    response._content = b'{"data": "test"}'
+    response.request = Mock()
+    response.request.method = "GET"
+    response.request.url = "http://test.com"
+    return response
+
+
+@pytest.fixture
+def mock_stream_response():
+    """Create a mock streaming httpx.Response object."""
+    response = Mock(spec=httpx.Response)
+    response.status_code = 200
+    response.headers = {}
+    response._content = b'data: {"content": "test"}\n\n'
+    response.request = Mock()
+    response.request.method = "POST"
+    response.request.url = "http://test.com/stream"
+    response.iter_lines = Mock(return_value=[b'data: {"content": "test"}\n\n'])
+    return response
+
+
+@pytest.fixture
+def mock_httpx_client():
+    """Create a mock httpx.Client."""
+    client = Mock(spec=httpx.Client)
+    client.is_closed = False
+    return client
+
+
+@pytest.fixture
+def sample_chat_response():
+    """Sample chat completion response data."""
+    return {
+        "id": "chatcmpl-123",
+        "object": "chat.completion",
+        "created": 1234567890,
+        "model": "gpt-3.5-turbo",
+        "choices": [
+            {
+                "index": 0,
+                "message": {
+                    "role": "assistant",
+                    "content": "Hello! How can I help you today?"
+                },
+                "finish_reason": "stop"
+            }
+        ],
+        "usage": {
+            "prompt_tokens": 10,
+            "completion_tokens": 20,
+            "total_tokens": 30
+        }
+    }
+
+
+@pytest.fixture
+def sample_chat_histories_response():
+    """Sample chat histories response data."""
+    return {
+        "data": [
+            {
+                "chatId": "chat-123",
+                "customTitle": "Test Chat",
+                "time": 1234567890,
+                "top": False
+            }
+        ],
+        "total": 1
+    }
+
+
+@pytest.fixture
+def sample_chat_records_response():
+    """Sample chat records response data."""
+    return {
+        "data": [
+            {
+                "dataId": "msg-123",
+                "content": {
+                    "text": "Hello!"
+                },
+                "time": 1234567890,
+                "feedback": {
+                    "userGoodFeedback": "Great!",
+                    "userBadFeedback": None
+                }
+            }
+        ]
+    }
+
+
+@pytest.fixture
+def sample_app_logs_response():
+    """Sample app logs chart response data."""
+    return {
+        "data": {
+            "users": {
+                "day": [
+                    {"time": "2024-01-01", "count": 10},
+                    {"time": "2024-01-02", "count": 15}
+                ]
+            },
+            "chats": {
+                "day": [
+                    {"time": "2024-01-01", "count": 25},
+                    {"time": "2024-01-02", "count": 30}
+                ]
+            },
+            "app": {
+                "day": [
+                    {"time": "2024-01-01", "count": 100},
+                    {"time": "2024-01-02", "count": 120}
+                ]
+            }
+        }
+    }
+
+
+@pytest.fixture
+def error_responses():
+    """Sample error response data."""
+    return {
+        "authentication_error": {
+            "code": "invalid_api_key",
+            "message": "Invalid API key",
+            "status": 401
+        },
+        "rate_limit_error": {
+            "code": "rate_limit_exceeded",
+            "message": "Rate limit exceeded",
+            "status": 429
+        },
+        "validation_error": {
+            "code": "invalid_parameters",
+            "message": "Invalid parameters",
+            "status": 422
+        },
+        "server_error": {
+            "code": "internal_error",
+            "message": "Internal server error",
+            "status": 500
+        }
+    }