Struct Harness 

pub struct Harness<A: App> { /* private fields */ }

A headless app under test. See the module docs for the model.

Implementations

impl<A: App> Harness<A>

where A::Msg: Send,

pub fn new(app: A, theme: Theme, size: (u32, u32)) -> Self

Builds the first frame. App::init runs with a collecting Proxy; proxied messages drain at every rebuild (after each input, Self::pump, or Self::update).

Panics

If no compute-capable GPU adapter exists.

pub fn rebuild(&mut self)

Rebuilds every window from current app state (proxied messages drain first) and reconciles the declared window set: new keys open, missing keys close (the active window falls back to main). Runs automatically after every input; call it yourself only after mutating via Self::app_mut.

pub fn activate_window(&mut self, key: &str)

Switches which window the verbs and queries target. Open windows come from App::windows; MAIN_WINDOW is always open.

Panics

If no open window has this key (the message lists the open ones).

pub fn window_keys(&self) -> Vec<String>

The keys of every open window, sorted (main first).

pub fn input(&mut self, event: InputEvent)

Dispatches one raw input event against the active window’s current frame, logs and applies the emitted messages, and rebuilds (which also reconciles the window set).

pub fn hover(&mut self, q: &Query)

Moves the pointer to the center of the matched node.

Panics

If the query matches zero or several nodes.

pub fn click(&mut self, q: &Query)

Clicks (press + release) the center of the matched node.

Panics

If the query matches zero or several nodes.

pub fn right_click(&mut self, q: &Query)

Right-clicks the center of the matched node.

Panics

If the query matches zero or several nodes.

pub fn double_click(&mut self, q: &Query)

Double-clicks the matched node (two clicks inside the double-click window — the harness clock does not advance).

Panics

If the query matches zero or several nodes.

pub fn triple_click(&mut self, q: &Query)

Triple-clicks the matched node (text inputs select the line).

Panics

If the query matches zero or several nodes.

pub fn shift_click(&mut self, q: &Query)

Clicks with Shift held (text inputs extend the selection from the caret to the click point).

Panics

If the query matches zero or several nodes.

pub fn type_text(&mut self, text: impl Into<String>)

Commits text to the focused element (like typing or IME commit).

pub fn key(&mut self, key: KeyInput)

Presses one key.

pub fn tab(&mut self)

Focuses the next focusable element (Tab).

pub fn shift_tab(&mut self)

Focuses the previous focusable element (Shift-Tab).

pub fn focus(&mut self, q: &Query)

Focuses the matched node directly (what assistive technology’s Focus action does). Prefer Self::tab to test the real path.

Panics

If the query matches zero or several nodes.

pub fn drag(&mut self, from: &Query, to: &Query)

Drags from one node to another: press on from, move to to (recomputed after the press, in case layout shifted), release.

Panics

If either query matches zero or several nodes.

pub fn drop_file(&mut self, q: &Query, path: impl Into<PathBuf>)

Drops an OS file onto the matched node.

Panics

If the query matches zero or several nodes.

pub fn wheel(&mut self, q: &Query, dy: f32)

Scrolls the wheel over the matched node (positive dy moves content down, winit convention).

Panics

If the query matches zero or several nodes.

pub fn pump(&mut self, ms: f64)

Advances the deterministic clock by ms milliseconds and rebuilds — animations and timers move exactly this far.

pub fn update(&mut self, msg: A::Msg)

Applies one message directly (as a proxy or window event would) and rebuilds. Not logged in Self::take_messages.

pub fn get(&self, q: &Query) -> AccessNode

The single matching node; panics (with the accessibility tree in the message) on zero or several matches.

Panics

If the query matches zero or several nodes.

pub fn query(&self, q: &Query) -> Option<AccessNode>

The single matching node, or None. Use to assert absence.

Panics

If the query matches several nodes.

pub fn get_all(&self, q: &Query) -> Vec<AccessNode>

Every matching node in tree order.

pub fn take_messages(&mut self) -> Vec<A::Msg>

Messages emitted by handlers since the last call (the Elm-level assertion: what the UI said, independent of state effects). Proxied and Self::update messages are inputs, not logged.

pub fn frame(&self) -> &Frame

The active window’s current frame, for direct queries and access_yaml().

pub fn app(&self) -> &A

The app under test.

pub fn app_mut(&mut self) -> &mut A

Mutable access to the app; call Self::rebuild afterwards.

pub fn render(&mut self) -> RgbaImage

Renders the active window to pixels. Mid-test captures are fine — the frame is not consumed.

Panics

If rendering fails.

pub fn render_window(&mut self, key: &str) -> RgbaImage

Renders any open window to pixels.

Panics

If no open window has this key, or rendering fails.