fission-test

Headless testing framework for Fission widgets.

fission-test lets you build, lay out, render, and interact with Fission widget trees without creating a window or GPU context. It provides HeadlessApp for lightweight lifecycle tests and TestDriver for full interaction-driven tests -- tapping buttons, typing text, scrolling, and asserting on visible output -- all running in-process with a mock text measurer and a TestRenderer that captures the display list.

Key types

Type	Description
`HeadlessApp<S>`	Owns an `GlobalState`, root widget, layout engine, and mock text measurer. Call `tick()` to advance the clock.
`TestDriver<S>`	High-level driver wrapping a `TestHarness`. Provides query methods (`find_text`, `find_role`, `get_all_visible_text`) and interaction methods (`tap_text`, `type_text`, `press_key`, `scroll_down`, `scroll_to_text`).
`TestRenderer`	A no-op `Renderer` implementation that stores the last `DisplayList` for inspection.
`TextMatch`	A query result containing the matched text, bounding rect, and node ID.
`SemanticMatch`	A query result containing the matched accessibility role, label, bounds, and node ID.

Usage example

use fission_test::{TestDriver, TestHarness};

let harness = TestHarness::new(MyState::default(), MyWidget);
let mut driver = TestDriver::new(harness);

driver.set_viewport(800.0, 600.0);
driver.pump()?;

// Assert text is rendered
driver.assert_text_visible("Hello, world!");

// Simulate a tap on a button
driver.tap_text("Submit")?;

// Verify state change
driver.assert_text_visible("Submitted!");

Environment variables

Variable	Effect
`FISSION_TEST_USE_MOCK_MEASURER=1`	Force the mock text measurer (10 px per char, 20 px line height).
`FISSION_TEST_MEASURER=mock`	Same as above.

Status

Supported -- actively used for widget and integration tests across the Fission workspace.

License