what test does Danforth devise to determine why Abigail was put out of the Proctor house?

In Act III, Danforth finds himself in unfamiliar
territory.  He, and the court, believing they have doing God's work and saving the
afflicted girls from the devilish witchcraft, are faced with Proctor's confession that
he has had a relationship with Abigail.  Knowing that the confession will soil his name,
and embarrass his family, Proctor confesses that he has "known" Abigail.  Abigail,
enraged, vehemently denies the accusation.  So what is Danforth to do?  He summons
Elizabeth (who has been in prison since Act II) to court.  He warns Abigail and Proctor
to turn their backs to Elizabeth and to make no motion or noise when she enters.  Calmly
he asks why Elizabeth fired young Abigail.  Elizabeth is now faced with a dilemma.  Does
she lie (remember Proctor has just told us that Elizabeth would never lie) in order to
protect her husband, or does she charge him with the crime of lechery in open court. 
Sadly, Elizabeth chooses to lie for her husband, and Danforth trick has worked.  In his
mind the evidence is clear- Abigail is innocent and Proctor has
lied.