One test, three durations

pytest parametrize runs one test body over a table of inputs. Copying the test three times drifts the day someone changes the assertion in only one copy. A value outside the legal range is a different test: it expects a reject.

HEATER_ON durations 1, 30, and 60 are legal. Duration 0 is not. Choose how the legal cases run, and what happens to 0.