An exemplary torque testing system includes a first screwdriver, a second screwdriver, a height measuring device, and a processor. The first screwdriver turns the first structure into the second structure using a maximum torque until the depth of the first structure turned into the second structure equals a predetermined minimum depth or the first structure is unable to be turned by the maximum torque. The second screwdriver turns the first structure into the second structure using a minimum torque until the first structure is unable to be turned by the minimum torque. The height measuring device measures the height of the combined first structure and second structure. The processor determines that the engagement between the first structure and the second structure is satisfactory, if the height of the combined first structure and second structure is in a range from a minimum height to a maximum height thereof.