Testing Typer CLI Apps in Python

If you'd like to package typer apps then you should also think about writing some unit tests for them. Thankfully, typer makes this easy for you by adding a TestClient to the framework.

Simple Test File

Here's an example of a test_cli.py tests file.

from typer.testing import CliRunner

from demopkg.__main__ import app

runner = CliRunner()


def test_app():
    result = runner.invoke(app, ["hello-world", "Vincent"])
    assert result.exit_code == 0
    assert "Vincent" in result.stdout


def test_db_create1():
    # Note that we need to confirm here, hence the extra input!
    result = runner.invoke(app, ["db", "create-db"], input="foobar\nfoobar\n")
    assert result.exit_code == 0
    assert "foobar" in result.stdout


def test_db_create2():
    # Note that we need to confirm here, hence the extra input!
    result = runner.invoke(app, ["db", "create-db", "--table", "foobar"], input="foobar\n")
    assert result.exit_code == 0
    print(result.stdout)
    assert "foobar" in result.stdout

These tests are just meant as an example but it's hopefully clear how these can be expanded. Note that we're using the input parameter in the running.invoke command in the latter two tests.

These tests can all be run by using pytest.

pytest

Again, if you want to see all the files you can get them from github.