Implement comprehensive unit test coverage for backend

backend/app/main.py

@@ -238,6 +238,9 @@ async def get_repository_info(
             raise HTTPException(status_code=404, detail="Repository not found")
 
         return RepositoryInfoResponse(**repo_data)
+    except HTTPException:
+        # Re-raise HTTPException without modification
+        raise
     except RuntimeError as e:
         error_msg = f"Error fetching repository info: {str(e)}"
         print(error_msg)

backend/pyproject.toml

@@ -19,3 +19,32 @@ disallow_incomplete_defs = true
 max-line-length = 88
 extend-ignore = "E203"
 exclude = [".git", "__pycache__", "build", "dist"]
+
+[tool.pytest.ini_options]
+minversion = "6.0"
+addopts = "-ra -q --tb=short"
+testpaths = [
+    "tests",
+]
+
+[tool.coverage.run]
+source = ["app"]
+omit = [
+    "*/tests/*",
+    "*/venv/*",
+    "*/__pycache__/*",
+]
+
+[tool.coverage.report]
+exclude_lines = [
+    "pragma: no cover",
+    "def __repr__",
+    "if self.debug:",
+    "if settings.DEBUG",
+    "raise AssertionError",
+    "raise NotImplementedError",
+    "if 0:",
+    "if __name__ == .__main__.:",
+    "class .*\\bProtocol\\):",
+    "@(abc\\.)?abstractmethod",
+]

backend/tests/README.md

@@ -0,0 +1,133 @@
+# Test Coverage Summary
+
+This document provides an overview of the unit test coverage added to the gitagu backend.
+
+## Test Structure
+
+```
+tests/
+├── __init__.py
+├── test_config.py              # Configuration module tests  
+├── test_constants.py           # Constants module tests
+├── test_main.py                # FastAPI endpoints tests
+├── test_models/
+│   ├── __init__.py
+│   └── test_schemas.py         # Pydantic model tests
+└── test_services/
+    ├── __init__.py
+    └── test_github.py          # GitHub service tests
+```
+
+## Test Statistics
+
+- **Total test files**: 5
+- **Total test cases**: 62
+- **Total lines of test code**: ~899 lines
+- **All tests passing**: ✅
+
+## Coverage Areas
+
+### 1. Pydantic Models (`test_models/test_schemas.py`) - 18 tests
+- ✅ RepositoryAnalysisRequest validation
+- ✅ RepositoryAnalysisResponse with various scenarios
+- ✅ RepositoryFileInfo with and without size
+- ✅ RepositoryInfoResponse complete and minimal
+- ✅ AnalysisProgressUpdate with details
+- ✅ Task breakdown models (Request, Task, Response)
+- ✅ Devin session models (Request, Response)
+- ✅ DevinSetupCommand model
+
+### 2. Configuration (`test_config.py`) - 5 tests
+- ✅ Default configuration values
+- ✅ Environment variable handling
+- ✅ Legacy Azure endpoint fallback
+- ✅ Azure model deployment name fallback
+- ✅ CORS origins configuration
+
+### 3. Constants (`test_constants.py`) - 5 tests
+- ✅ Agent ID constants
+- ✅ Legacy agent ID mapping
+- ✅ Dependency files list
+- ✅ Language mapping for dependency files
+- ✅ Language map completeness validation
+
+### 4. GitHub Service (`test_services/test_github.py`) - 17 tests
+- ✅ `_safe_int_conversion` utility function (7 tests)
+- ✅ GitHubService initialization
+- ✅ GitHub client creation with/without token
+- ✅ RepositoryFileInfo model integration
+- ✅ Base64 encoding/decoding handling
+- ✅ Dependency files processing
+- ✅ GitHub URL constants
+- ✅ Mock response structure validation
+- ✅ README response structure
+- ✅ Tree response structure
+
+### 5. FastAPI Endpoints (`test_main.py`) - 17 tests
+
+#### Basic Endpoints (4 tests)
+- ✅ Root endpoint (`/`)
+- ✅ Health check endpoint (`/health`)
+- ✅ CORS headers handling
+- ✅ 404 for nonexistent endpoints
+
+#### Repository Analysis (3 tests)
+- ✅ Successful analysis with mocked services
+- ✅ Invalid request validation (422 error)
+- ✅ Error handling during analysis
+
+#### Repository Info (3 tests)
+- ✅ Successful repository info retrieval
+- ✅ Repository not found (404)
+- ✅ Service error handling (500)
+
+#### Task Breakdown (3 tests)
+- ✅ Successful task breakdown
+- ✅ Invalid request validation
+- ✅ Service error handling
+
+#### Devin Session (2 tests)
+- ✅ Invalid request validation
+- ✅ Valid request structure validation
+
+#### Dependency Injection (2 tests)
+- ✅ GitHub service creation
+- ✅ Agent service function validation
+
+## Testing Approach
+
+### Mocking Strategy
+- **External APIs**: Mocked using `unittest.mock`
+- **Dependencies**: FastAPI dependency overrides for clean testing
+- **Async functions**: Proper AsyncMock usage for async service methods
+- **File operations**: No actual file I/O in tests
+
+### Test Organization
+- **Unit tests**: Isolated testing of individual components
+- **Integration tests**: Testing of endpoint behavior with mocked dependencies
+- **Validation tests**: Pydantic model validation and error handling
+- **Edge cases**: NULL values, missing fields, error conditions
+
+### Code Quality
+- **No modifications to production code** except:
+  - Fixed HTTPException handling in repository info endpoint
+  - Added pytest configuration to pyproject.toml
+- **Comprehensive mocking** for external dependencies
+- **Clear test structure** with descriptive test names
+- **Setup/teardown** properly implemented for stateful tests
+
+## Test Execution
+
+All tests pass successfully and can be run with:
+```bash
+pytest tests/ -v
+```
+
+Tests cover the core functionality of:
+- Request/response validation
+- Service layer interactions  
+- Configuration handling
+- Error scenarios
+- External API mocking
+
+This provides a solid foundation for future development and ensures the reliability of the backend API.

backend/tests/__init__.py

@@ -0,0 +1 @@
+# Tests package

backend/tests/test_config.py

@@ -0,0 +1,81 @@
+"""Tests for the configuration module."""
+import os
+import pytest
+from unittest.mock import patch
+
+
+class TestConfig:
+    """Test configuration loading and defaults."""
+
+    @patch.dict(os.environ, {}, clear=True)
+    def test_default_config_values(self):
+        """Test that default configuration values are set correctly."""
+        # Force reload the config module to pick up cleared environment
+        import importlib
+        from app import config
+        importlib.reload(config)
+
+        assert config.PROJECT_ENDPOINT is None
+        assert config.MODEL_DEPLOYMENT_NAME == "gpt-4o"
+        assert config.AZURE_AI_PROJECT_CONNECTION_STRING is None
+        assert config.AZURE_AI_AGENTS_API_KEY is None
+        assert config.GITHUB_TOKEN is None
+        assert config.GITHUB_API_URL == "https://api.github.com"
+        assert "http://localhost:5173" in config.CORS_ORIGINS
+        assert "https://gitagu.com" in config.CORS_ORIGINS
+
+    @patch.dict(os.environ, {
+        "PROJECT_ENDPOINT": "https://test.ai.azure.com",
+        "MODEL_DEPLOYMENT_NAME": "gpt-3.5-turbo",
+        "AZURE_AI_AGENTS_API_KEY": "test-key",
+        "GITHUB_TOKEN": "github-token"
+    })
+    def test_config_with_environment_variables(self):
+        """Test configuration with environment variables set."""
+        # Force reload the config module to pick up new environment
+        import importlib
+        from app import config
+        importlib.reload(config)
+
+        assert config.PROJECT_ENDPOINT == "https://test.ai.azure.com"
+        assert config.MODEL_DEPLOYMENT_NAME == "gpt-3.5-turbo"
+        assert config.AZURE_AI_AGENTS_API_KEY == "test-key"
+        assert config.GITHUB_TOKEN == "github-token"
+
+    @patch.dict(os.environ, {
+        "AZURE_AI_PROJECT_CONNECTION_STRING": "https://legacy.ai.azure.com"
+    })
+    def test_legacy_azure_endpoint_fallback(self):
+        """Test that legacy Azure endpoint is used as fallback."""
+        # Force reload the config module
+        import importlib
+        from app import config
+        importlib.reload(config)
+
+        assert config.AZURE_AI_PROJECT_CONNECTION_STRING == "https://legacy.ai.azure.com"
+
+    @patch.dict(os.environ, {
+        "AZURE_AI_MODEL_DEPLOYMENT_NAME": "custom-model"
+    })
+    def test_azure_model_deployment_name_fallback(self):
+        """Test Azure model deployment name fallback."""
+        # Force reload the config module
+        import importlib
+        from app import config
+        importlib.reload(config)
+
+        assert config.MODEL_DEPLOYMENT_NAME == "custom-model"
+
+    def test_cors_origins_configuration(self):
+        """Test CORS origins configuration."""
+        from app import config
+
+        expected_origins = [
+            "http://localhost:5173",
+            "https://gitagu.com",
+            "https://agunblock.com",
+            "*"
+        ]
+
+        for origin in expected_origins:
+            assert origin in config.CORS_ORIGINS

backend/tests/test_constants.py

@@ -0,0 +1,53 @@
+"""Tests for the constants module."""
+from app.constants import (
+    AGENT_ID_GITHUB_COPILOT_COMPLETIONS,
+    AGENT_ID_GITHUB_COPILOT_AGENT,
+    AGENT_ID_DEVIN,
+    AGENT_ID_CODEX_CLI,
+    AGENT_ID_SREAGENT,
+    LEGACY_AGENT_ID_MAP,
+    DEPENDENCY_FILES,
+    LANGUAGE_MAP,
+)
+
+
+class TestConstants:
+    """Test application constants."""
+
+    def test_agent_ids(self):
+        """Test that agent ID constants are defined correctly."""
+        assert AGENT_ID_GITHUB_COPILOT_COMPLETIONS == 'github-copilot-completions'
+        assert AGENT_ID_GITHUB_COPILOT_AGENT == 'github-copilot-agent'
+        assert AGENT_ID_DEVIN == 'devin'
+        assert AGENT_ID_CODEX_CLI == 'codex-cli'
+        assert AGENT_ID_SREAGENT == 'sreagent'
+
+    def test_legacy_agent_id_mapping(self):
+        """Test legacy agent ID mapping."""
+        assert 'github-copilot' in LEGACY_AGENT_ID_MAP
+        assert LEGACY_AGENT_ID_MAP['github-copilot'] == AGENT_ID_GITHUB_COPILOT_COMPLETIONS
+
+    def test_dependency_files(self):
+        """Test dependency files list."""
+        expected_files = ["requirements.txt", "package.json", "pom.xml", "build.gradle"]
+        assert DEPENDENCY_FILES == expected_files
+        assert len(DEPENDENCY_FILES) == 4
+
+    def test_language_mapping(self):
+        """Test language mapping for dependency files."""
+        expected_mappings = {
+            "requirements.txt": "Python",
+            "package.json": "JavaScript/TypeScript",
+            "pom.xml": "Java",
+            "build.gradle": "Java/Kotlin",
+        }
+        assert LANGUAGE_MAP == expected_mappings
+
+        # Test that all dependency files have language mappings
+        for dep_file in DEPENDENCY_FILES:
+            assert dep_file in LANGUAGE_MAP
+
+    def test_language_map_completeness(self):
+        """Test that all dependency files have corresponding language mappings."""
+        for dependency_file in DEPENDENCY_FILES:
+            assert dependency_file in LANGUAGE_MAP, f"Missing language mapping for {dependency_file}"