A mold system for forming a casting article for investment casting in which the mechanical integrity of a ceramic core can be tested by viscosity manipulation. A method for testing a ceramic core used for an investment casting includes: positioning the ceramic core within a mold for receiving a sacrificial material fluid to form a sacrificial material on at least a portion of the ceramic core, the ceramic core having a predefined layout; during casting of the sacrificial material fluid about the ceramic core using the mold, controlling a viscosity of the sacrificial material fluid to simulate an expected viscosity of a molten metal used during a subsequent investment casting using the ceramic core; and evaluating mechanical damage to at least one region of the ceramic core caused by the casting of the sacrificial material fluid.