'proven in practice' is a correct and usable phrase in written English.
You can use it to refer to something that has been successfully tested in a real-world situation. Here is an example sentence: The effectiveness of the new drug has been proven in practice through clinical trials.
The mayor can question Boris' competence, but his own incompetence is proven in practice.
Mr. Zyuganov's first deputy, Ivan Melnikov, told the congress, "Now we must react more promptly, because the Kremlin's calculations that its candidate will automatically get the rating of the current president is a theory which has yet to be proven in practice".
"If the frequency and spread of events accelerates and they become more contentious, the resilience for providing cross-border support will not only be tested but potentially undermined when the arrangements put in place by forces have not been proven in practice," he said.
The boiler design should be proven in practice to be rugged and reliable.
Its success has been proven in practice with the development of a DpDt system for dredgers.
In various places, it is mentioned that the fractional derivative portrays the memory effect, which has not been proven in practice.
There is a question, however, about how extensive the savings will prove in practice.
Science was enhanced, not damaged, if theories could be proved in practice.
That is because these motives have often proved, in practice, to be in conflict with each other.
"Now the challenge is on for us all to prove in practice that we can all work together to build a positive future for our industry, our members and the public whom we serve".
Sadly it's rather more interesting in theory than it proves in practice in an unevenly cast production where the Chinese elements don't always sit as comfortably or naturally as they might well have done in the original Hong Kong staging.
