Session state changes within button `onclick` not making it back to AppTest instance

Using Streamlit
,
1

Hello,
I’ve started using AppTest to test my streamlit app and it seems that a button’s onclick isn’t actually triggered by AppTest when using click().
I’m using Streamlit 1.31

Here’s an example. If my test functions uses if button to mutate session state, the test passes:

from streamlit.testing.v1 import AppTest

def test_testing():
    def test_fn():
        import streamlit as st

        st.session_state["clicked"] = False
        if st.button("Click me", key="button_key"):
            st.session_state["clicked"] = True

    at = AppTest.from_function(test_fn)
    at.run()

    assert at.session_state["clicked"] is False
    at.button("button_key").click().run()
    assert at.session_state["clicked"] is True

However, if I instead use onclick:

from streamlit.testing.v1 import AppTest

def test_testing():
    def test_fn():
        import streamlit as st

        def toggle():
            st.session_state["clicked"] = not st.session_state["clicked"]

        st.session_state["clicked"] = False
        st.button("Click me", key="button_key", on_click=toggle)

    at = AppTest.from_function(test_fn)
    at.run()

    assert at.session_state["clicked"] is False
    at.button("button_key").click().run()
    assert at.session_state["clicked"] is True

then the test fails.

Am I missing something, or is that something that AppTest cannot handle yet?

2

I can actually put a breakpoint inside the toggle function and the debugger does break on it, so toggle is actually executed.

It just seems like the session state update within toggle doesn’t make it back to the AppTest session state.

3

Closing this – the issue is that this line

st.session_state["clicked"] = False

gets run on every run of the app, including after clicking the button. That’s why the session state switches back to False.
I just need to Streamlit’s “re-run all on every interaction” behavior, including in tests.

4

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