Add command to overwrite one property in fixture

[Tymoteusz Stępień]

-> readFile testData
example testData

{name: "John", surname: "Doe"}

-> you do an update of this name in the object you pulled from testData
changing name in testData obj we got

{name: "Max", surname: "Doe"}

-> you writeFile the updated object that overwrites the old one in testData
we got in testData

{name: "Max", surname: "Doe"}