Here is an example of a mutation report showing that a mutation eliminating an HTML attribute that survived:

This is showing that the code:

        <Button style={{ float: "right" }} as={Link} to="/hotels/create">

Was mutated to the following (removing float: "right"), without any tests failing (i.e. “the mutant survived”).

        <Button style={{  }} as={Link} to="/hotels/create">

To fix this, you can add this to your test, where thisButton is a handle to the button in question:

        expect(thisButton).toHaveAttribute("style", "float: right;");

For example, here’s what that looks like in context.

With screen included in the import from @testing-library/react:

import { fireEvent, render, waitFor, screen } from "@testing-library/react";

We can write:

    const createHotelButton = screen.getByText("Create Hotel");
    expect(createHotelButton).toBeInTheDocument();
    expect(createHotelButton).toHaveAttribute("style", "float: right;");