Just a quick clarification: if you have just 1 response, it's just regular ANCOVA or ANOVA. The "M" is for "Multivariate" which specifically means multiple response variables. The distinction is important because you would use a different platform.
You can use Fit Model for the analysis. Include the main effects for your independent variable and the covariate in the model. Including the interaction between those factors will allow you to test if the slope for pre-tests scores is consistent across the different levels of your categorical factor.