Struct TestBackend 

pub struct TestBackend { /* private fields */ }

Headless rendering backend for tests.

Renders a UI closure to an in-memory Buffer without a real terminal. Use render to run one frame, then inspect the output with line, assert_contains, or to_string_trimmed.

Example

use slt::TestBackend;

let mut backend = TestBackend::new(40, 10);
backend.render(|ui| {
    ui.text("hello");
});
backend.assert_contains("hello");

Implementations

impl TestBackend

pub fn new(width: u32, height: u32) -> Self

Create a test backend with the given terminal dimensions.

pub fn render(&mut self, f: impl FnOnce(&mut Context))

Run a UI closure for one frame and render to the internal buffer.

pub fn render_with_events( &mut self, events: Vec<Event>, focus_index: usize, prev_focus_count: usize, f: impl FnOnce(&mut Context), )

Render with injected events and focus state for interaction testing.

pub fn run_with_events( &mut self, events: Vec<Event>, f: impl FnOnce(&mut Context), )

Convenience wrapper: render with events using default focus state.

pub fn line(&self, y: u32) -> String

Get the rendered text content of row y (trimmed trailing spaces)

pub fn assert_line(&self, y: u32, expected: &str)

Assert that row y contains expected as a substring

pub fn assert_line_contains(&self, y: u32, expected: &str)

Assert that row y contains expected as a substring

pub fn assert_contains(&self, expected: &str)

Assert that any line in the buffer contains expected

pub fn buffer(&self) -> &Buffer

Access the underlying render buffer.

pub fn width(&self) -> u32

Terminal width used for this backend.

pub fn height(&self) -> u32

Terminal height used for this backend.

pub fn to_string_trimmed(&self) -> String

Return the full rendered buffer as a multi-line string.

Each row is trimmed of trailing spaces and joined with newlines. Useful for snapshot testing with insta::assert_snapshot!.

Trait Implementations

impl Display for TestBackend

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.