App testing

Streamlit app testing framework enables developers to build and run headless tests that execute their app code directly, simulate user input, and inspect rendered outputs for correctness.

The provided class, AppTest, simulates a running app and provides methods to set up, manipulate, and inspect the app contents via API instead of a browser UI. It can be used to write automated tests of an app in various scenarios. These can then be run using a tool like pytest. A typical pattern is to build a suite of tests for an app that ensure consistent functionality as the app evolves, and run the tests locally and/or in a CI environment like Github Actions.

The AppTest class

st.testing.v1.AppTest

st.testing.v1.AppTest simulates a running Streamlit app for testing.

from streamlit.testing.v1 import AppTest

at = AppTest.from_file("streamlit_app.py")
at.secrets["WORD"] = "Foobar"
at.run()
assert not at.exception

at.text_input("word").input("Bazbat").run()
assert at.warning[0].value == "Try again."

AppTest.from_file

st.testing.v1.AppTest.from_file initializes a simulated app from a file.

from streamlit.testing.v1 import AppTest

at = AppTest.from_file("streamlit_app.py")
at.secrets["WORD"] = "Foobar"
at.run()
assert not at.exception

AppTest.from_string

st.testing.v1.AppTest.from_string initializes a simulated app from a string.

from streamlit.testing.v1 import AppTest

app_script = """
import streamlit as st

word_of_the_day = st.text_input("What's the word of the day?", key="word")
if word_of_the_day == st.secrets["WORD"]:
    st.success("That's right!")
elif word_of_the_day and word_of_the_day != st.secrets["WORD"]:
    st.warn("Try again.")
"""

at = AppTest.from_string(app_script)
at.secrets["WORD"] = "Foobar"
at.run()
assert not at.exception

AppTest.from_function

st.testing.v1.AppTest.from_function initializes a simulated app from a function.

from streamlit.testing.v1 import AppTest

def app_script ():
    import streamlit as st

    word_of_the_day = st.text_input("What's the word of the day?", key="word")
    if word_of_the_day == st.secrets["WORD"]:
        st.success("That's right!")
    elif word_of_the_day and word_of_the_day != st.secrets["WORD"]:
        st.warn("Try again.")

at = AppTest.from_function(app_script)
at.secrets["WORD"] = "Foobar"
at.run()
assert not at.exception

Testing-element classes

Block

A representation of container elements, including:

st.chat_message
st.columns
st.sidebar
st.tabs
The main body of the app.

# at.sidebar returns a Block
at.sidebar.button[0].click().run()
assert not at.exception

Element

The base class for representation of all elements, including:

st.title
st.header
st.markdown
st.dataframe

# at.title returns a sequence of Title
# Title inherits from Element
assert at.title[0].value == "My awesome app"

Button

A representation of st.button and st.form_submit_button.

at.button[0].click().run()

ChatInput

A representation of st.chat_input.

at.chat_input[0].set_value("What is Streamlit?").run()

Checkbox

A representation of st.checkbox.

at.checkbox[0].check().run()

ColorPicker

A representation of st.color_picker.

at.color_picker[0].pick("#FF4B4B").run()

DateInput

A representation of st.date_input.

release_date = datetime.date(2023, 10, 26)
at.date_input[0].set_value(release_date).run()

Multiselect

A representation of st.multiselect.

at.multiselect[0].select("New York").run()

NumberInput

A representation of st.number_input.

at.number_input[0].increment().run()

Radio

A representation of st.radio.

at.radio[0].set_value("New York").run()

SelectSlider

A representation of st.select_slider.

at.select_slider[0].set_range("A","C").run()

Selectbox

A representation of st.selectbox.

at.selectbox[0].select("New York").run()

Slider

A representation of st.slider.

at.slider[0].set_range(2,5).run()

TextArea

A representation of st.text_area.

at.text_area[0].input("Streamlit is awesome!").run()

TextInput

A representation of st.text_input.

at.text_input[0].input("Streamlit").run()

TimeInput

A representation of st.time_input.

at.time_input[0].increment().run()

Toggle

A representation of st.toggle.

at.toggle[0].set_value("True").run()

Previous: Configuration Next: st.testing.v1.AppTest

forum

Still have questions?

Our forums are full of helpful information and Streamlit experts.