move progress bar test to correct test folder (#5667)

tests/trainer/logging_/test_progress_bar_logging.py

@@ -0,0 +1,22 @@
+import pytest
+
+from pytorch_lightning import Trainer
+from tests.base import BoringModel
+
+
+def test_logging_to_progress_bar_with_reserved_key(tmpdir):
+    """ Test that logging a metric with a reserved name to the progress bar raises a warning. """
+    class TestModel(BoringModel):
+
+        def training_step(self, *args, **kwargs):
+            output = super().training_step(*args, **kwargs)
+            self.log("loss", output["loss"], prog_bar=True)
+            return output
+
+    model = TestModel()
+    trainer = Trainer(
+        default_root_dir=tmpdir,
+        max_steps=2,
+    )
+    with pytest.warns(UserWarning, match="The progress bar already tracks a metric with the .* 'loss'"):
+        trainer.fit(model)