Testing

ui.NewTester runs a view without a window, as fast as a unit test: it renders frames in memory, finds elements by their text, and clicks, types, scrolls and presses keys.

func TestCounter(t *testing.T) {
	app := &counter{}
	tt := ui.NewTester(app.view, 320, 240)
	if err := tt.Click("Increment"); err != nil {
		t.Fatal(err)
	}
	if app.n != 1 || !tt.HasText("1") {
		t.Errorf("count %d, texts %q", app.n, tt.Texts())
	}
}

Elements are found by their text, or by their Label for those without, as an icon button: tt.Click("Close"), tt.Find("Volume"), tt.Focused("Name").

Two elements given the same Key under one parent share one state, so that a click or the focus meant for one goes to the other: a tester panics where the second key was given, as apps only log it.

What a tester does

• Pointer. tt.Click, tt.ClickAt, tt.ClickWith(ui.Shift, "Row 3"), tt.Press, tt.Move and tt.Release, and tt.Scroll.
• Keyboard. tt.Key(ui.Cmd, ui.KeyS) presses a key, tt.TypeKey a key with the text it types, and tt.Type types text into the focused element. tt.Compose shows the composition of an input method, tt.Command performs an edit command of the menus, such as "copy", and tt.TextCaret returns where input methods would compose.
• Menus. tt.RightClick opens a context menu, which tt.Menu lists and tt.ChooseMenuItem("Move to", "Archive") chooses from.
• The window. tt.SetSize, tt.SetScale, tt.SetDark and tt.SetPreferences change the window and the desktop's settings; tt.SetFocused takes the keyboard from the window and gives it back.
• What it shows. tt.Texts, tt.HasText, tt.Find (the box of a text), tt.Focused, tt.Cursor, tt.Clipboard, tt.OpenedURLs and tt.Announcements, what the view asked screen readers to read out.
• Frames. tt.Frame draws a frame, for what changed outside the view, and tt.Image() is the last frame, for snapshots; ui.Render draws a view once at a given scale.