“At Cornhill we sometimes use the crèche test.
A young mother has left her baby in the crèche for the first time; during the sermon she is paying at most 30% attention, because she is worrying about her baby.
When she goes to the crèche at the end, a crèche helper asks her about the sermon.
If she says, “Well, it all sounded good and worthy, and he said a lot of things, but I don’t really know what he said” it’s a failure.
If she says, “I missed a fair bit of it, but the big thrust was this…” (and gets it right), and the big thrust of the sermon is the main thrust of the passage, hey presto! the whole exercise looks more promising.”