Constable Sukhdev Vishnoi participated in running test impersonating as one Naresh Vishnoi, police said.
Naresh's uncle Rajaram Bishnoi, a head constable, was engaged in arrangement for the recruitment and had allegedly asked Sukhdev to run at the place of his nephew.
However, someone complained to senior officers following which the matter came into light and all of them were arrested, police said.
They will be produced in a local court tomorrow.