Bacterial Evolution

Out of Creationist curiosity I took a look at the website Conservepedia. I was confused by a statement made as fact, but unfortunately not backed up by data, that evolution has never been shown in the lab.

In the spirit of full disclosure, I admit I am a biologist with considerable experience in microbiology, immunology, and virology. To say that evolution has never been shown in the lab is a bit startling considering that even the layman knows that bacteria easily mutate into antibiotic resistant strains. Labs are where these evolving bacteria are studied.

The very definition of evolution is the ability of organisms to adapt to a changing environment, i.e. developing antibiotic resistance, through mutation.

Am I missing something? Please explain.