The poem "Barbie Doll" by Marge Piercy tells the story of a young girls who is told she has a "big nose" and "fat legs." Despite all evidence to the contrary, this young girl believed the lie and committed suicide. This is a tragic story of unrealistic expectations, as demonstrated first by the title. Barbie is the epitome of unrealistic expectations.
The phrase you ask about is found in the second stanza of the poem. Here the speaker outlines all the fine qualities of this young girl.
She was healthy, tested intelligent,
possessed strong arms and back,
abundant sexual drive and manual dexterity.
This girl is in good health, is bright, is physically fit, and has normal desires and coordination. The "tested intelligent" obviously refers to her intellectual capacity; she is capable of learning.
The tragedy of this poem is that a perfectly "normal" girl was persuaded to believe she was not by a few careless words spoken by a young classmate.
"Barbie Doll" by Marge Piercy describes a girl who tries to live up to the ideal image of a beautiful girl as shown by the doll named Barbie. The girl is healthy and strong and "tested intelligent." This line literally means that she takes tests and does well. She is smart and does well in school. This is not a characteristic that seems to be valued in women, but rather is only valued in men.
When connecting this line with the line that follows later in the stanza "she went to and fro apologizing," it suggests that the girl must feel sorry for her intelligence, health and strength. This girl needs to focus on her beauty and making sacrifices in order to look like the ideal woman.
The article in the link below (second link) by Chris Semansky goes into further depth on the issue of intelligent women in a male-driven society. It is an interesting take on the subject and deals further with the quote you are speaking of.