In the courtroom proceedings, Danforth has laid down several "tests" for those who wish to even bring the slightest amount of concern or questioning to the court. On one hand, Danforth lays down the test for Francis Nurse that if he submits the petition with 91 signatures on it as testament to the goodness of those who are imprisoned, that those 91 people can be brought in now for questioning. He lays down a similar test for Corey in demanding to know the name of the informant from who he received information about Putnam's overall desires having nothing to do with witchcraft but land acquisition. He lays down a similar challenge for Proctor to see if he wishes to clear his wife or bring suspicion to the court. In the end, Danforth's ultimate test to all is the assertion that people are "either with this court or against it." In this, Danforth has constructed a setting whereby the voice of dissent is seen as subversive.
This is the background to the test that Mary Warren must endure. He recognizes that Warren has signed a deposition that claims her initial testimony and that of Abigail and the other girls is fraudulent. He wishes to "test" her by making her publicly confess in front of Abigail and the other girls. Danforth has already seen that Mary is sick and weak, as evidenced by Proctor continually physically holding her up in court and Danforth himself saying, "She's not well." He is conscious of the fact that she is a "shaky" witness at best. In bringing her to the court and demanding that she confront the other girls, en masse, becomes the test that he places on Mary. He probably knows that she won't pass it, and in doing so, his court is validated and Proctor's case against it invalidated. In the end, this is what results with Proctor himself confessing to all that is charged against him, if only to stop the court's pretenses of pursuing truth and justice.