The Lab isn't a normal level, but rather a debugging tool. The Lab allows the player to save programs for automatic verification of functionality.
The expect keyword allows verifying the internal value of components. It applies starting after the execution of the next instruction. It takes two arguments, the first being the index of the linked component and the second the correct value. The value is checked after every instruction, so if the value changes again, a new expect line must be provided.
The set_input keyword allows providing custom input values, allowing testing of input related instructions.