If there is a reaction, the most obvious evidence is a color change.
CuSO4 in water is an indescribable blue. In fact it is nicknamed bluestone.
If it reacts to become CuCO3 the color goes to green.
A second piece of evidence is that the CuCO3 is insoluble in a water solution. It will form a precipitate. CuSO4 is very soluble so not only will the color disappear it will be a green solid on the bottom of the container.
