What are some examples of irony in Act 2 of The Importance of Being Earnest by Oscar Wilde?

In Act 2 of The Importance of Being Earnest, Oscar Wilde gains most of his humor through situational irony, that is, things that are the opposite of what is expected. At the beginning of the scene, Miss Prism scorns "this modern mania for turning bad people into good people at a moment's notice." This is ironic in two respects: first, most people would favor a sinner's reformation and second, true reformation rarely happens instantaneously.

Next Cecily admonishes Algy, who is pretending to be Ernest, "I hope you have not been leading a double life, pretending to be wicked and being really good all the time. That would be hypocrisy." Again, the irony works on two levels: first, the usual way a hypocrite acts is to pretend to be good while really being wicked, and second, Algy actually is pretending here, although Cecily doesn't know it. That is dramatic irony, where the audience knows something a character doesn't.

When Algy says that good looks "are a snare that every sensible man would like to be caught in," his remark is ironic in that a snare, by definition, takes one against one's will.

Miss Prism, upon learning that Ernest is dead, says, "What a lesson for him! I trust he will profit by it." Her remark is humorously ironic since dead men cannot profit from life's lessons.

Jack's unthinking reply to Cecily, "I haven't got a brother!" is ironic in that without realizing it he denies the lie that he has worked so hard to perpetrate, and when he tells the literal truth, Cecily won't accept it, mistaking his answer for a figurative disowning of his brother.

Cecily's long explanation of her fantasy romance with Ernest to Algernon, who is pretending to be Ernest, is highly ironic as Algy learns about things in "his" past that he has done from a woman he has only just met. Gwendolen's description of her father's role is ironic because it exchanges the expected role in society of men with that of women: "The home seems to me to be the proper sphere for the man."

The conversation between Gwendolyn and Cecily about their engagements is hilariously ironic since each of them believes the other woman is speaking of the same man when they are really only speaking of the same imaginary character who is being played by two different men.

The tea war is ironic since taking tea is usually a genteel occasion, but here it becomes aggressive, yet cloaked in exaggerated civility.

In Act 2, Wilde takes the audience on a wild ironic ride, careening from one unexpected twist to another.