The proof of the pudding is in the eating

Origin
William Camden stated it in 1605 in Remaines of a Greater Worke, Concerning Britaine.
Explanation
It is said to mean that you can only judge the quality of something after you have tried, used or experienced it. A dish may have been made from a good recipe with fresh ingredients and look delicious, but you can really only judge it by putting it in your mouth. The actual taste is the only true criterion of success. The proof refers to the quality, the reliability of a material product like the pudding and it could be directly experienced by the simple act of eating and the taste sensation it imparts is like any other valid scientific observation, a simple experiment to establish the truth.The real value of something can be judged only from practical experience or results and not from appearance or theory.The end result or finished product determines success or failure. The true value or quality of something can only be judged when it’s put to use; the results are what counts.
Examples
Theory says that this material will produce a superior widget, but the proof of the pudding is in the eating.
I know you didn’t think it was a very good product, but just look at the fantastic sales figures. That’s the proof of the pudding is in the eating.
Go ahead—talk all you want about your wonderful recipe and its fine ingredients, but ultimately the proof of the pudding is in the eating.