diff --git a/cf_xarray/accessor.py b/cf_xarray/accessor.py
index 21feb6ff..602801c3 100644
--- a/cf_xarray/accessor.py
+++ b/cf_xarray/accessor.py
@@ -796,7 +796,6 @@ def _guess_bounds(da, dim=None, out_dim="bounds"):
                 f"If dim is None, variable {da.name} must be 1D or 2D. Received {da.ndim}D variable instead."
             )
         dim = da.dims
-
     if not isinstance(dim, str):
         if len(dim) > 2:
             raise NotImplementedError(
diff --git a/cf_xarray/geometry.py b/cf_xarray/geometry.py
index 6e4f1090..442e632b 100644
--- a/cf_xarray/geometry.py
+++ b/cf_xarray/geometry.py
@@ -586,7 +586,11 @@ def points_to_cf(
         coord = None
         pts_ = pts
 
-    x, y, node_count, crdX, crdY = [], [], [], [], []
+    x: list[np.ndarray] = []
+    y: list[np.ndarray] = []
+    node_count: list[int] = []
+    crdX: list[float] = []
+    crdY: list[float] = []
     for pt in pts_:
         if isinstance(pt, MultiPoint):
             xy = np.concatenate([p.coords for p in pt.geoms])
diff --git a/cf_xarray/helpers.py b/cf_xarray/helpers.py
index 1053a55b..747f111c 100644
--- a/cf_xarray/helpers.py
+++ b/cf_xarray/helpers.py
@@ -34,7 +34,7 @@ def _guess_bounds_1d(da, dim):
     result = xr.concat([first, bounds], dim=dim).transpose(..., "bounds")
     if ADDED_INDEX:
         result = result.drop_vars(dim)
-    return result
+    return result.drop_attrs(deep=False)
 
 
 def _guess_bounds_2d(da, dims):
diff --git a/cf_xarray/tests/test_accessor.py b/cf_xarray/tests/test_accessor.py
index 3b65fbc6..58a811bf 100644
--- a/cf_xarray/tests/test_accessor.py
+++ b/cf_xarray/tests/test_accessor.py
@@ -832,6 +832,9 @@ def test_add_bounds(dims):
         assert_allclose(
             added[name].reset_coords(drop=True), expected[dim].transpose(..., "bounds")
         )
+        if dim == "lat":
+            # The CF axes shouldn't have changed
+            assert added.cf.axes["Y"] == ["lat"]
 
     _check_unchanged(original, ds)
 
diff --git a/cf_xarray/units.py b/cf_xarray/units.py
index e1d553e8..7f0fb281 100644
--- a/cf_xarray/units.py
+++ b/cf_xarray/units.py
@@ -60,7 +60,7 @@ def short_formatter(unit, registry, **options):
 # Reused with modification from MetPy under the terms of the BSD 3-Clause License.
 # Copyright (c) 2015,2017,2019 MetPy Developers.
 # Create registry, with preprocessors for UDUNITS-style powers (m2 s-2) and percent signs
-units = pint.UnitRegistry(
+units: pint.UnitRegistry = pint.UnitRegistry(
     autoconvert_offset_to_baseunit=True,
     preprocessors=[
         functools.partial(
diff --git a/pyproject.toml b/pyproject.toml
index a496e8b1..ad90d566 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -107,7 +107,6 @@ docstring-code-format = true
 
 
 [tool.pytest]
-python_files = "test_*.py"
 testpaths = ["cf_xarray/tests"]
 
 [tool.rstcheck]