RandomForestClassifier test df formatino

I am trying to predict the classification of a dependent variable into one of four categories using the RF Classifier library and after pre-formatting my test and train datasets and running fit() I get this error when trying to predict:

ValueError: Number of features of the model must match the input. Model n_features is 26 and input n_features is 27

Should my test df have an empty column for the y variable? How should I be calling .predict() for classification?