Tracking a circling plane

A few weeks ago, a Blue Dart aircraft was approaching the Chennai airport from the Guindy side. Soon, it aborted landing and flew away.
The onlookers’ imagination soared along with the Boeing 757-23N aircraft. Why did it abort landing?
“The pilot must have seen a dog on the runway,” one opined.
“Maybe there was an airport vehicle or another aircraft on the runway,” said the other.
After five minutes or so, the same aircraft approached the airport and aborted landing again. “Something is wrong with the plane,” all onlookers said in a chorus.
The circling continued a few more times, and there was no sign of the aircraft for a long time after that. What happened?
One of them checked a flight tracking site and found the aircraft making a wider circle this time. “It will come back soon,” he said, adding, “They may be doing some training or testing. They can do it now as not much air traffic is there.”
“Oh! Then nothing to worry,” one said with a sigh.
The aerial circus was not a one day event. The aircraft still circles over the city on most days.