Assert the layout editor reports (or does not report) unsaved changes: the warning it shows from the first change until "Save layout" or "Cancel".
Examples
Then the layout should have unsaved changes
Then the layout should not have unsaved changes
And the layout should have unsaved changes
Then the layout editor should have unsaved changes
And the layout editor should not have unsaved changes
Pattern
Then(/^the layout(?: editor)? should( not)* have unsaved changes$/, …)
Part of @webship-js/backdrop-cms-steps (github.com/webship/backdrop-cms-steps), a step pack for Webship-js 2.0.x.