"tests indicated" is correct and usable in written English.
You can use it when you want to say that tests provided evidence for something. For example, "Tests indicated that the patient had a high fever."
But tests indicated that it wasn't.
Ground radar tests indicated a likelihood that the grave remained.
Tests indicated highly reactive, unstable snow — no real surprise.
Preliminary tests indicated that the worker had cutaneous anthrax, Mr. Skinner said.
Officials said tests indicated a petroleum distillate had been spread in the house.
But later tests indicated that he had an unusual manifestation of inhalation anthrax, Dr. Hughes said.
Initial tests indicated that both women had contracted the West Nile virus.
Blood tests indicated Ms. Leon might also have the auto-immune disorder.
Subsequent tests indicated blood-lead levels so high they resulted in the boy's hospitalization.
And another hospital employee who had a suspicious lesion was not infected, tests indicated.
Blood tests indicated that the blood cells that fight infection were quite elevated.
