@lfoppiano My favorite technique for testing a component is making an example app and then using using playwright to check the output of a component on the app – here’s an example streamlit-folium/tests/test_frontend.py at master · randyzwitch/streamlit-folium · GitHub and another example st_pages/tests/test_frontend.py at main · blackary/st_pages · GitHub
If it interacts with normal streamlit widgets, you could also potentially use the app testing framework, but that is not designed to work with 3rd party components directly.