The expression "Canary in a Coalmine" refers to a live experiment serving to others. Old days, coal miners used to get a canary with them to work it seems. Canary was recognized to be very susceptible to toxic gases. The bird used to sing all day long and if the amount of toxicity in the mine increased, it stopped singing and died due to poisonous gas. This served as a warning to the miners.
This expression has become popular to refer to any experiment in real world contexts. For e.g. Chrome Browser use of TimerDelay function. (I stumbled upon this phrase in the linked article).