factor out fname check when no splitting occurs

mne/tests/test_epochs.py

@@ -1556,16 +1556,9 @@ def test_split_saving(tmp_path, epochs_to_split, preload):
 def test_split_naming(tmp_path, epochs_to_split):
     """Test naming of the split files."""
     epochs, _, n_files = epochs_to_split
-    # Check that if BIDS is used and no split is needed it defaults to
-    # simple writing without _split- entity.
     split_fname = tmp_path / "test_epo.fif"
     split_fname_neuromag_part1 = tmp_path / f"test_epo-{n_files + 1}.fif"
     split_fname_bids_part1 = tmp_path / f"test_split-{n_files + 1:02d}_epo.fif"
-
-    epochs.save(split_fname, split_naming="bids", verbose=True)
-    assert split_fname.is_file()
-    assert not split_fname_bids_part1.is_file()
-    os.remove(split_fname)
     # we don't test for reserved files as it's not implemented here
 
     epochs.save(split_fname, split_size="1.4MB", verbose=True)
@@ -1583,6 +1576,20 @@ def test_split_naming(tmp_path, epochs_to_split):
     assert split_fname_bids_part1.is_file()
 
 
+def test_saved_fname_no_splitting(tmp_path, epochs_to_split):
+    """Test saved fname doesn't get split suffix when splitting not needed."""
+    # Check that if BIDS is used and no split is needed it defaults to
+    # simple writing without _split- entity.
+    epochs, _, n_files = epochs_to_split
+    split_fname = tmp_path / "test_epo.fif"
+    split_fname_bids_part1 = tmp_path / f"test_split-{n_files + 1:02d}_epo.fif"
+
+    epochs.save(split_fname, split_naming="bids", verbose=True)
+
+    assert split_fname.is_file()
+    assert not split_fname_bids_part1.is_file()
+
+
 @pytest.mark.parametrize("split_naming", ["neuromag", "bids"])
 def test_saving_fails_with_not_permitted_overwrite(
         tmp_path, epochs_factory, split_naming