Offering a hint as to the United Federation of Teachers’ next agenda item, and a window into the thinking of the union’s prominent president, Randi Weingarten, the city union is unveiling a new television advertising campaign on the subject of standardized testing.

Tests are not enough to improve learning; teachers and students also need a “well-rounded curriculum,” the advertisement says.

As the camera follows a young girl planting seeds in a vase, a voice says, “Standardized school tests can measure her progress in certain subjects. But New York City teachers believe it takes a well-rounded curriculum — including science, civics, language arts, and sports — to help young imaginations thrive.”

Testing has become more commonplace and more significant in the five years since Mayor Bloomberg took control of the schools, with Chancellor Joel Klein closing schools based on low test scores; tying cash incentives to performance on tests, and ramping up the number of tests given, saying educators can use the data to individualize their teaching.

Ms. Weingarten, whose name is displayed with the UFT logo during the new advertisement, has distinguished herself from some union leaders by not dismissing testing wholesale. She was a partner in the pay plan that is giving some teachers bonuses this year in part based on test results.

Ms. Weingarten’s position on the issue of testing is likely to be closely inspected if she seeks the presidency of her parent union, the American Federation of Teachers.

The current president, Edward McElroy, recently announced his plans to retire, leaving Ms. Weingarten his likely successor. Ms. Weingarten said she is considering trying for the job.