Where tests live

• Main TUI tests: crates/but/src/command/legacy/status/tui/tests/
• Test harness/helpers: crates/but/src/tui/test_utils.rs and crates/but/src/command/legacy/status/tui/tests/utils.rs
• Snapshots: crates/but/src/command/legacy/status/tui/tests/snapshots/

Basic pattern

#[test]
fn describes_behavior_under_test() {
    let env = Sandbox::init_scenario_with_target_and_default_settings("one-stack").unwrap();
    env.setup_metadata(&["A"]).unwrap();

    let mut tui = test_status_tui(env);

    tui.input_then_render(KeyCode::Down)
        .assert_rendered_term_svg_eq(file!["snapshots/describes_behavior_under_test_001.svg"]);
}

Driving the TUI

Useful input examples:

tui.input_then_render(None);                                       // render without inputs
tui.input_then_render('j');                                        // single char input
tui.input_then_render(KeyCode::Down);                              // special key
tui.input_then_render(Shift('j'));                                 // keys with shift
tui.input_then_render(Control('j'));                               // keys with control
tui.input_then_render([KeyCode::Down, KeyCode::Down]);             // multiple keys from array
tui.input_then_render("commit message text");                      // multiple keys from string
tui.reload();                                                      // reload state after making external changes

Assertions

Generally prefer

• assert_current_line_eq(str![...]) for cursor/selection behavior.
• assert_rendered_term_svg_eq(file!["snapshots/test_function_name_001.svg"]) for everything else.

Generally you should include one assert_rendered_term_svg_eq per logical group of inputs, to catch bad states early.

Be careful using assert_rendered_contains and assert_rendered_not_contains since they might lead to false positives. They're intended to use while iterating on a test where snapshots would cause too much churn.

Read crates/but/src/tui/test_utils.rs and crates/but/src/command/legacy/status/tui/tests/utils.rs for more specialized assertions.

You're not allowed to add new kinds of assertions to crates/but/src/tui/test_utils.rs or crates/but/src/command/legacy/status/tui/tests/utils.rs. Rely entirely on the existing assertions.

Running tests

• cargo test -p but <test-name> to run one test.
• SNAPSHOTS=overwrite cargo test -p but <test-name> to run and update snapshots.
• cargo test -p but tui to run all tui tests. Do this after changing things.

If a test fails the output will include the rendered state of the test backend. This can be used when iterating on a test as a way of inspecting the state.