whats an example in The Importance of Being Earnest of dramatic irony

One example of dramatic irony in The Importance of Being Earnest is when Algernon pretends to be Ernest in order to woo Cecily. This leads to humorous confusion because Jack (who also goes by Ernest) arrives and is shocked to discover that someone else has been pretending to be him. The audience is aware of the deception, while the characters remain oblivious, which creates a sense of tension and anticipation.