The test of metal hydroxides and metal oxides

Is testing metal oxide different from testing metal hydroxide using a litmus paper?

Litmus paper does not test for either metal oxides or metal hydroxides; indeed, it will not change color at all. Try it: put dry $$\ce{CaO}$$ on dry litmus paper. Litmus does change color with pH+, the negative log10 ratio of $$\ce{H+}$$ ions to $$\ce{OH-}$$ ions (the ions may actually be more complex, such as $$\ce{H3O+}$$, but the idea is the same). This means the substance is in aqueous solution, i.e. in water.
Litmus also changes color with non-metals in solution, such as $$\ce{NH3}$$, which forms $$\ce{NH4OH}$$ in water, or with acetic acid, having an excess of $$\ce{H+}$$ ions.