Yes, a reaction occurs when NiCl2(aq) is added to a test tube containing Zn(NO3)2(aq). The reaction that takes place is a single-replacement reaction, in which the more reactive metal (Zn) replaces the less reactive metal (Ni) in the compound. The products of the reaction are zinc chloride (ZnCl2) and nickel nitrate (Ni(NO3)2). The net ionic equation for the reaction is:

Zn(s) + Ni²⁺(aq) → Zn²⁺(aq) + Ni(s)

In this reaction, zinc metal acts as the reducing agent, while nickel ions act as the oxidizing agent. The reaction can be observed as a change in the color of the solution from green (nickel ions) to colorless (zinc ions).