At least that's how it seems to work in the test tube.

She had a rack of test tubes at her feet.

"Why does my teacher not get me to use any of those to clean test tubes?"

"Is it true you were created in a test tube?"

Who would have ever expected him to break the test tube he was supposed to hand over?

She set the test tube in its tray and stood.

"What happened when they put the blood in the test tube?"

But most research has been done on animals or in test tubes, not people.

"I do not want him putting this in a test tube."

This would appear as a single line in the test tube.