Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Put a (silver) (salad) fork in it: this satire is done.
Wilde’s main point in The Importance of Being Earnest is to criticize Victorian society by showing how shallow and hypocritical is it. What do aristocrats do all day? Play the piano, visit their scandalous neighbors, gossip about their scandalous neighbors, eat cucumber sandwiches, and make up lies to avoid dining with their relatives.
Oh yeah—and say incredibly callous and catty things. Take, for example, the moment when Lady Bracknell tells everyone blithely that she was visiting Lady Harbury, who "looks quite twenty years younger" since "her poor husband’s death" (I.111).
And what does Lady Bracknell want to see in Jack, her future son-in-law? Money, property, stylishness, and an aristocratic name. His character or morals? Pshaw. What character? What morals?
As the play goes on and we see just how shallow everyone’s desires are, and we tend to laugh. Wilde does not allow his tone to get too heavy or dark. Instead, we find the characters in The Importance of Being Earnest hi-larious.