fix: improve macOS C++ compatibility and add CI tests

tests/README.md

@@ -0,0 +1,52 @@
+# LEANN Tests
+
+This directory contains automated tests for the LEANN project, primarily used in CI/CD pipelines.
+
+## Test Files
+
+### `test_ci_basic.py`
+Basic functionality tests that verify:
+- All packages can be imported correctly
+- C++ extensions (FAISS, DiskANN) load properly
+- Basic index building and searching works for both HNSW and DiskANN backends
+
+### `test_main_cli.py`
+Tests the main CLI example functionality:
+- Tests with facebook/contriever embeddings
+- Tests with OpenAI embeddings (if API key is available)
+- Verifies that normalized embeddings are detected and cosine distance is used
+
+## Running Tests Locally
+
+### Basic tests:
+```bash
+python tests/test_ci_basic.py
+```
+
+### Main CLI tests:
+```bash
+# Without OpenAI API key
+python tests/test_main_cli.py
+
+# With OpenAI API key
+OPENAI_API_KEY=your-key-here python tests/test_main_cli.py
+```
+
+## CI/CD Integration
+
+These tests are automatically run in the GitHub Actions workflow:
+1. After building wheel packages
+2. On multiple Python versions (3.9 - 3.13)
+3. On both Ubuntu and macOS
+
+### Known Issues
+
+- On macOS, there might be C++ standard library compatibility issues that cause tests to fail
+- The CI is configured to continue on macOS failures to avoid blocking releases
+- OpenAI tests are skipped if no API key is provided in GitHub secrets
+
+## Test Data
+
+Tests use the example data in `examples/data/`:
+- `PrideandPrejudice.txt` - Text file for testing
+- PDF files for document processing tests