Revert "Remove redundant README_TESTS.md"

This reverts commit 5e538c4.

Author: jontsai

README_TESTS.md

@@ -0,0 +1,84 @@
+# Running Tests
+
+## Quick Start (Using Make)
+
+The easiest way to run tests:
+
+```bash
+# First time setup - create virtual environment
+make venv
+source .venv/bin/activate
+
+# Install dependencies
+make install
+
+# Run all tests
+make test
+
+# Run just the catalog vendor tests
+make test-vendor
+
+# Run tests with coverage
+make test-cov
+```
+
+## Manual Test Commands
+
+If you prefer to run pytest directly:
+
+```bash
+# Activate virtual environment
+source .venv/bin/activate
+
+# Run catalog extra fields tests
+python -m pytest tests/test_vendor/test_catalog_v1.py -v
+```
+
+## All Test Commands
+
+```bash
+# Run all catalog vendor tests
+python -m pytest tests/test_vendor/ -v
+
+# Run specific test file
+python -m pytest tests/test_vendor/test_catalog_v1.py -v
+
+# Run specific test class
+python -m pytest tests/test_vendor/test_catalog_v1.py::TestMetadataExtraFields -v
+
+# Run specific test method
+python -m pytest tests/test_vendor/test_catalog_v1.py::TestMetadataExtraFields::test_metadata_accepts_extra_fields -v
+
+# Run with more verbose output
+python -m pytest tests/test_vendor/test_catalog_v1.py -vv
+
+# Run and show print statements
+python -m pytest tests/test_vendor/test_catalog_v1.py -v -s
+
+# Run all tests in the project
+python -m pytest tests/ -v
+```
+
+## Using tox (Recommended for full test suite)
+
+The GitHub Actions CI uses tox to run tests across multiple Python and Pydantic versions:
+
+```bash
+# Run tests with Python 3.10 and Pydantic 2.10 (no coverage)
+python3 -m tox -e py310-pydantic210-nocov
+
+# Run tests with coverage
+python3 -m tox -e py310-pydantic210-cover
+
+# Run specific tests with tox
+python3 -m tox -e py310-pydantic210-nocov -- tests/test_vendor/test_catalog_v1.py
+```
+
+## Continuous Integration
+
+Tests run automatically on every push and pull request via GitHub Actions (`.github/workflows/github-actions.yml`).
+
+The CI runs tests across:
+- Python versions: 3.10, 3.11, 3.12, PyPy 3.10
+- Pydantic versions: 2.8, 2.10
+- With and without coverage reports