diff --git a/src/GOSTnets/core.py b/src/GOSTnets/core.py
index 567f7ee..506fa75 100644
--- a/src/GOSTnets/core.py
+++ b/src/GOSTnets/core.py
@@ -3615,7 +3615,7 @@ def project_gdf(gdf, to_crs=None, to_latlong=False):
 
     # otherwise, automatically project the gdf to UTM
     else:
-        if ox.CRS.from_user_input(gdf.crs).is_projected:
+        if ox.projection.is_projected(gdf.crs):
             raise ValueError("Geometry must be unprojected to calculate UTM zone")
 
         # calculate longitude of centroid of union of all geometries in gdf
@@ -3766,7 +3766,7 @@ def find_kne(point, lines, near_idx):
 
     """
     # getting the distances between the point and the lines
-    dists = np.array(list(map(lambda line: line.distance(point), lines)))
+    dists = np.array(lines.distance(point))
     kne_pos = dists.argsort()[0]
     kne = lines.iloc[kne_pos]
     kne_idx = near_idx[kne_pos]
@@ -3865,6 +3865,10 @@ def update_nodes(
         The updated nodes GeoDataFrame.
 
     """
+    ### NOTES
+    # node_highway_pp and node_highway_poi are not both needed, they are
+    # used conditionally depending on the ptype, so the parameters should be updated
+
     # create gdf of new nodes (projected PAPs)
     if ptype == "pp":
         new_nodes = gpd.GeoDataFrame(new_points, columns=["geometry"], crs=measure_crs)
@@ -3918,6 +3922,12 @@ def update_edges(edges, new_lines, replace=True, nodes_meter=None, pois_meter=No
         kne_idx refers to 'fid in Rtree'/'label'/'loc', not positional iloc
 
     """
+    ### NOTES
+    # line_pps_dict is never defined, where did it come from?
+    # same for 'itertools', 'measure_crs', 'pois', 'poi_key_col', 'oneway_tag',
+    # 'road_col', 'edge_highway', 'factor', 'u_tag', 'v_tag', 'nodes_id_dict',
+    # 'threshold', and maybe additional variables... DID THIS FUNCTION EVER WORK?
+
     # for interpolation (split by pp): replicate old line
     if replace:
         # create a flattened gdf with all line segs and corresponding kne_idx
diff --git a/tests/test_core.py b/tests/test_core.py
index 70234e9..ea0a1b8 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -391,6 +391,13 @@ def test_project_gdf():
     projected_gdf = core.project_gdf(gdf, to_crs="epsg:32633", to_latlong=False)
     # check the output
     assert projected_gdf.crs == "epsg:32633"
+    # with invalid CRS
+    gdf_invalid = gpd.GeoDataFrame({"geometry": [Point(0, 0), Point(1, 1)]}, crs=None)
+    with pytest.raises(ValueError):
+        core.project_gdf(gdf_invalid, to_crs="epsg:32633", to_latlong=False)
+    # with no "to_crs" parameter
+    utm_gdf = core.project_gdf(gdf, to_latlong=False)
+    assert "utm" in utm_gdf.crs.to_string()
 
 
 def test_euclidean_distance():
@@ -857,3 +864,42 @@ def test_clip():
     assert G_clip.nodes(data=True) != G.nodes(data=True)
     assert G_clip.edges(data=True) != G.edges(data=True)
     assert G_clip.number_of_nodes() < G.number_of_nodes()
+
+
+def test_find_kne():
+    """Test the find_kne function."""
+    # define a point
+    point = Point(0.5, 0.6)
+    # define some lines
+    line1 = LineString([(0, 0), (1, 1)])
+    line2 = LineString([(1, 1), (2, 2)])
+    line3 = LineString([(2, 2), (3, 3)])
+    # put lines in a geodataframe
+    gdf = gpd.GeoDataFrame({"geometry": [line1, line2, line3]})
+    # call function
+    kne_idx, kne = core.find_kne(point, gdf, [0, 1, 2])
+    assert isinstance(kne_idx, int)
+    assert isinstance(kne, pd.Series)
+    assert kne_idx == 0
+
+
+def test_get_pp():
+    """Test the get_pp function."""
+    # define a point
+    point = Point(0.5, 0.6)
+    # define the line
+    line = LineString([(0, 0), (1, 1)])
+    # call the function
+    pp = core.get_pp(point, line)
+    assert isinstance(pp, Point)
+    assert pp.x == 0.55
+    assert pp.y == 0.55
+
+
+def test_split_line_error():
+    """Test the split_line function error handling."""
+    # define line
+    line = LineString([(0, 0), (1, 1)])
+    # call function
+    with pytest.raises(TypeError):
+        core.split_line(line, "invalid")
diff --git a/tests/test_core_integrative.py b/tests/test_core_integrative.py
index 1e2b664..0b48117 100644
--- a/tests/test_core_integrative.py
+++ b/tests/test_core_integrative.py
@@ -80,3 +80,17 @@ def test_edges_nodes_df_to_graph_03(self):
         G = core.edges_and_nodes_gdf_to_graph(nodes_df, edges_df, largest_G=True)
         # assert that the function returned a nx graph this time
         assert isinstance(G, nx.Graph)
+
+    def test_edges_nodes_df_to_graph_04(self):
+        # read csv files as dfs
+        nodes_df = pd.read_csv(self.fpath_nodes)
+        edges_df = pd.read_csv(self.fpath_edges)
+        # switch stnode and endnode to floats
+        edges_df["stnode"] = edges_df["stnode"].astype(float)
+        edges_df["endnode"] = edges_df["endnode"].astype(float)
+        # call function with adding missing reflected edges and the oneway tag
+        G = core.edges_and_nodes_gdf_to_graph(
+            nodes_df, edges_df, add_missing_reflected_edges=True, oneway_tag="one_way"
+        )
+        # assert that the function returned a nx graph this time
+        assert isinstance(G, nx.Graph)