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Pyzedv1.9.0

Tests and screenshots

app.screenshot(path) renders the app’s current state off-screen and saves a PNG. It needs no window, display or GPU (it uses the software renderer), so it works in CI.

app = MyApp()
app.items = ["one", "two"]          # set up the state you want to show
app.screenshot("docs/list.png", size=(480, 320), scale=2)
  • size: logical size; defaults to App.size.
  • scale: PNG pixel density (2 = retina).
  • wait: seconds to wait before capturing, in case on_start started some work.

Every image in this documentation is generated this way:

Windows, macOS and Linux
uv run python examples/screenshots.py              # large screenshots (docs/screenshots)
uv run python docs/scripts/component_shots.py      # component illustrations

Testing the logic

Section titled “Testing the logic”

Since the state lives in your object, update and callbacks are tested like plain Python:

def test_counter():
    app = Counter()
    app.update("increment")
    app.update("increment")
    assert app.count == 2

Testing that the view renders

Section titled “Testing that the view renders”

view() must return a Widget without raising. A screenshot makes a good smoke test:

def test_view_renders(tmp_path):
    app = MyApp()
    app.screenshot(tmp_path / "ui.png", size=(800, 600))
    assert (tmp_path / "ui.png").stat().st_size > 0

If view() raises, the screenshot shows the traceback instead of the UI, just like the window.