Update Readme so that .test will work. (#659)

When one follows the Readme, the example will fail once we call `trainer.test()` because the methods are not overridden. Fixes #428

Author: Frédéric Branchaud-Charron

README.md

@@ -128,6 +128,18 @@ To use lightning do 2 things:
  avg_loss = torch.stack([x['val_loss'] for x in outputs]).mean()
  tensorboard_logs = {'val_loss': avg_loss}
  return {'avg_val_loss': avg_loss, 'log': tensorboard_logs}
+ 
+ def test_step(self, batch, batch_idx):
+ # OPTIONAL
+ x, y = batch
+ y_hat = self.forward(x)
+ return {'test_loss': F.cross_entropy(y_hat, y)}
+ 
+ def test_end(self, outputs):
+ # OPTIONAL
+ avg_loss = torch.stack([x['test_loss'] for x in outputs]).mean()
+ tensorboard_logs = {'test_loss': avg_loss}
+ return {'avg_test_loss': avg_loss, 'log': tensorboard_logs}
 
  def configure_optimizers(self):
  # REQUIRED