Refactor conftest.py for clarity and functionality

Updated comments and descriptions for clarity. Adjusted the logic for skipping tests based on the presence of GEMINI_API_KEY.

Author: imohitseth

conftest.py

@@ -1,29 +1,44 @@
 """
-Pytest configuration for AST-Healer.
+Root conftest.py for AST-Healer.
 
-Tests that invoke the Gemini API are skipped automatically in CI
-when GEMINI_API_KEY is not set as a repository secret.
+Executed by pytest before any test collection. Handles two things:
+1. Injects the google.antigravity stub into sys.path so CI can import
+   main.py and app.py without the real Gemini SDK installed.
+2. Auto-skips any test marked @pytest.mark.requires_api_key when
+   GEMINI_API_KEY is absent.
 """
 
 import os
-import pytest
+import sys
+from pathlib import Path
+
+# Inject the google.antigravity stub BEFORE any project module is imported.
+# The stub lives at tests/mocks/ and is only activated when the real package is not already installed.
+try:
+    import google.antigravity  # noqa: F401 — real package found, nothing to do
+except ImportError:
+    stub_path = str(Path(__file__).parent / "tests" / "mocks")
+    if stub_path not in sys.path:
+        sys.path.insert(0, stub_path)
+
+# Custom markers
+import pytest  # noqa: E402 — must come after path manipulation
 
 
 def pytest_configure(config):
-    """Register custom markers."""
     config.addinivalue_line(
         "markers",
-        "requires_api_key: mark test as requiring GEMINI_API_KEY to run",
+        "requires_api_key: skip this test when GEMINI_API_KEY is not set",
     )
 
 
 def pytest_collection_modifyitems(config, items):
-    """Skip LLM tests when API key is absent."""
+    """Auto-skip LLM integration tests in CI when no API key is present."""
     api_key = os.environ.get("GEMINI_API_KEY", "").strip()
     if not api_key:
-        skip_marker = pytest.mark.skip(
+        skip = pytest.mark.skip(
             reason="GEMINI_API_KEY not set — skipping LLM integration tests"
         )
         for item in items:
             if "requires_api_key" in item.keywords:
-                item.add_marker(skip_marker)
+                item.add_marker(skip)