The pioneering Silicon Valley Internet firm was looking at whether having a mix of players handling search results or search ad placement at its websites would benefit Yahoo and its users.
"As we work to create the absolute best experiences for Yahoo users, from time to time, we run small tests with a variety of partners including search providers," a Yahoo spokesperson said, noting that Google was among those search firms.
"There is nothing further to share at this time."
Microsoft and Yahoo updated their search partnership in April to allow more flexibility in searches and end Yahoo's exclusive sales force role with advertisers.
The search partnership between Microsoft and Yahoo took effect in 2010 and was supposed to last 10 years, but Yahoo had the option of exiting it midway if certain revenue conditions were not met. Yahoo's chief executive, Marissa Mayer, had repeatedly signaled that she was dissatisfied.
Google, the search leader, was expected to take a 54.5 percent of the global market this year, the research firm said.