Fix README example and add test to run python-code example in CI

CHANGELOG.md

@@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [unreleased](https://github.com/mllam/weather-model-graphs/compare/v0.2.0...HEAD)
 
+### Added
+
+- added test to check python codeblocks in README keep working as code changes
+  [\#38](https://github.com/mllam/weather-model-graphs/pull/38) @leifdenby
+
 
 ## [v0.2.0](https://github.com/mllam/weather-model-graphs/releases/tag/v0.2.0)
 

tests/test_readme.py

@@ -0,0 +1,21 @@
+import re
+from pathlib import Path
+
+import pytest
+
+
+def _parse_readme_examples():
+    lines = open(Path(__file__).parent.parent / "README.md").read().splitlines()
+
+    # use regex to find all python code blocks
+    code_blocks = re.findall(r"```python(.*?)```", "\n".join(lines), re.DOTALL)
+
+    return code_blocks
+
+
+@pytest.mark.parametrize("codeblock_example", _parse_readme_examples())
+def test_readme_example(codeblock_example: str):
+    """
+    Check that execution of the python code block in the README does not raise an exception.
+    """
+    exec(codeblock_example)