Agree. It's a matter of taste and habbit ;) Thanks.

Prefer initial return false, as it helps to understand what the method is expected to return

Updated the line with the one you suggested. The description already specifies the coins available "But vending machine has only 25, 10, 5 and 1 cents available." I am afraid not all non-native speakers know the words: dimes, nickles etc, so I prefer to leave it as it is. But thanks for your suggestion.

Updated

Fixed. Try once more, please

C#

Using random for tests is bad practice.

Either add the note about the optimization to the task, or add the big test to the sample tests.

In C# version the method name should start with a capital letter accroding to .NET convention