Snape's repsonse to the firework wasn't unfair but the way he instantly goes to Harry is. Snape has no proof that it was Harry who threw it. The fact that Harry did it is immatieral - Snape has no reason to assume Harry did except that he doesn't like him.
Snape also never found out that Harry did it (unless it was in Harry's memories) or why - the Polyjuice Potion was between Harry, Ron and Hermione. None of the teachers ever found out about it.
My guess is that Snape volenteered. He does know a lot about duelling. Lockhart probably also voleenteered and then took over in his usual manner.
I think that saying Snape was trying to test Harry for Parseltongue is giving Snape too much credit. I think he was bitter about the firework and wanted to get Harry in some way. The snake would be alarming for everyone and also would leave Harry somewhat in Snape's debt (in Snape's eyes anyway) if Snape had to get rid of it. He also wanted Malfoy to win and he knew there was almost certainly nothing Harry could do against the snake. The fact that it then revealed Harry was a Parselmouth was an added bonus.
no subject
Snape also never found out that Harry did it (unless it was in Harry's memories) or why - the Polyjuice Potion was between Harry, Ron and Hermione. None of the teachers ever found out about it.
My guess is that Snape volenteered. He does know a lot about duelling. Lockhart probably also voleenteered and then took over in his usual manner.
I think that saying Snape was trying to test Harry for Parseltongue is giving Snape too much credit. I think he was bitter about the firework and wanted to get Harry in some way. The snake would be alarming for everyone and also would leave Harry somewhat in Snape's debt (in Snape's eyes anyway) if Snape had to get rid of it. He also wanted Malfoy to win and he knew there was almost certainly nothing Harry could do against the snake. The fact that it then revealed Harry was a Parselmouth was an added bonus.