Transform test data when using a persistent model
In the same way that you use joblib to persist your saved model, you should persist the transformers that you use in the pipeline too. So for example if you're using StandardScaler() and OneHotEncoder(), those also need to be joblib.dump()ed so you can import them into your prediction script.

The simplest way to achieve this is to add both transformers and estimator into a Scikit Learn pipeline and use joblib to persist that.