question: fast_dev_run does not execute pl.LightningModule.test_step()
context: I may be misunderstanding something about the trainer argument fast_dev_run. When I provide fast_dev_run=1 and I add a print statement in my LightningModule's test_step function, the print statement does not appear. In addition, I can see a progress bar for my training set and validation set, but no progress bar appears for the test set.
  Is fast_dev_run actually running n batches of my training set? I have passed in a DataModule to trainer.fit() that includes a test_dataloader.
answer: fit only runs training & validation, not testing.
  trainer.test runs the test_step