First cup
Set the dial to 80 %.
The kettle is heating.
Set the dial to 0 %. Then press reset.
The kettle is off.
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How this is tested passed
This tutorial is also an acceptance test. Its report has every step, check and screenshot from the last run.
The user story: As a tea drinker, I want to start the kettle by turning the dial, so that it works like the one I already have.
When the dial is 80 % Then the kettle is heating When the dial is 0 % And the user presses reset Then the kettle is off