diff --git a/src/GOSTnets/core.py b/src/GOSTnets/core.py
index 38646b5..57f633b 100644
--- a/src/GOSTnets/core.py
+++ b/src/GOSTnets/core.py
@@ -695,16 +695,14 @@ def graph_nodes_intersecting_polygon(G, polygons, crs=None):
         a list of the nodes intersecting the polygons
 
     """
-    if type(G) == nx.classes.multidigraph.MultiDiGraph:
+    if isinstance(G, nx.Graph):
         graph_gdf = node_gdf_from_graph(G)
-
-    elif type(G) == gpd.geodataframe.GeoDataFrame:
+    elif isinstance(G, gpd.GeoDataFrame):
         graph_gdf = G
-
     else:
         raise ValueError("Expecting a graph or node geodataframe for G!")
 
-    if type(polygons) != gpd.geodataframe.GeoDataFrame:
+    if type(polygons) != gpd.GeoDataFrame:
         raise ValueError("Expecting a geodataframe for polygon(s)!")
 
     if (crs is not None) and (graph_gdf.crs != crs):
@@ -751,13 +749,13 @@ def graph_edges_intersecting_polygon(G, polygons, mode, crs=None, fast=True):
         a list of the edges intersecting the polygons
 
     """
-    if type(G) == nx.classes.multidigraph.MultiDiGraph:
+    if isinstance(G, nx.Graph):
         node_graph_gdf = node_gdf_from_graph(G)
         edge_graph_gdf = edge_gdf_from_graph(G)
     else:
         raise ValueError("Expecting a graph for G!")
 
-    if type(polygons) != gpd.geodataframe.GeoDataFrame:
+    if type(polygons) != gpd.GeoDataFrame:
         raise ValueError("Expecting a geodataframe for polygon(s)!")
 
     if (crs is not None) and (node_graph_gdf.crs != crs):
diff --git a/tests/test_core.py b/tests/test_core.py
index c2ed75b..a36601e 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -87,25 +87,30 @@ def mocked_convert(x, y, z, f, g):
     return ["one", "two", "three"]
 
 
-@mock.patch("GOSTnets.core.convert", mocked_convert)
-def test_combo_csv_to_graph():
-    """Test the combo_csv_to_graph function."""
-    # create the test csv object
-    f_df = pd.DataFrame(
-        data={"u_col": ["a", "b", "c"], "v_col": ["x", "y", "z"], "geo_col": [1, 2, 3]}
-    )
-    # write to buffer
-    s_buf = io.StringIO()
-    f_df.to_csv(s_buf)
-    s_buf.seek(0)
-    # call function
-    G = core.combo_csv_to_graph(
-        s_buf, u_tag="u_col", v_tag="v_col", geometry_tag="geo_col"
-    )
-    # assertions
-    assert isinstance(G, nx.MultiDiGraph)
-    assert "a" in G.nodes
-    assert "x" in G.nodes
+class TestGraphCreationFunctions:
+    @mock.patch("GOSTnets.core.convert", mocked_convert)
+    def test_combo_csv_to_graph(self):
+        """Test the combo_csv_to_graph function."""
+        # create the test csv object
+        f_df = pd.DataFrame(
+            data={
+                "u_col": ["a", "b", "c"],
+                "v_col": ["x", "y", "z"],
+                "geo_col": [1, 2, 3],
+            }
+        )
+        # write to buffer
+        s_buf = io.StringIO()
+        f_df.to_csv(s_buf)
+        s_buf.seek(0)
+        # call function
+        G = core.combo_csv_to_graph(
+            s_buf, u_tag="u_col", v_tag="v_col", geometry_tag="geo_col"
+        )
+        # assertions
+        assert isinstance(G, nx.MultiDiGraph)
+        assert "a" in G.nodes
+        assert "x" in G.nodes
 
 
 def test_edges_and_nodes_gdf_to_graph():
@@ -118,24 +123,53 @@ def test_edges_and_nodes_csv_to_graph():
     pass
 
 
-def test_node_gdf_from_graph():
-    """Test the node_gdf_from_graph function."""
-    pass
-
-
-def test_edge_gdf_from_graph():
-    """Test the edge_gdf_from_graph function."""
-    pass
-
-
-def test_graph_nodes_intersecting_polgyon():
-    """Test the graph_nodes_intersecting_polgyon function."""
-    pass
-
-
-def test_graph_edges_intersecting_polgyon():
-    """Test the graph_edges_intersecting_polgyon function."""
-    pass
+class TestGDFfromGraph:
+    # create graph to use for tests
+    G = nx.Graph()
+    # add some nodes w/ (x, y) attributes
+    G.add_node(1, x=0, y=0)
+    G.add_node(2, x=-1, y=0.3)
+    G.add_node(3, x=2, y=0.17)
+    G.add_node(4, x=4, y=0.255)
+    G.add_node(5, x=5, y=0.03)
+    # create some edges
+    G.add_edge(1, 2)
+    G.add_edge(4, 5)
+    # define polygon
+    poly = Polygon([(-1, -1), (0.0, 1.0), (1.0, 0.0)])
+    poly_gdf = gpd.GeoDataFrame({"x": 1, "geometry": poly}, index=[1])
+
+    def test_node_gdf_from_graph(self):
+        """Test the node_gdf_from_graph function."""
+        node_gdf = core.node_gdf_from_graph(self.G)
+        assert isinstance(node_gdf, gpd.GeoDataFrame)
+        assert "x" in node_gdf.columns
+        assert "y" in node_gdf.columns
+        assert "geometry" in node_gdf.columns
+        assert node_gdf.shape[0] == 5
+
+    def test_edge_gdf_from_graph(self):
+        """Test the edge_gdf_from_graph function."""
+        edge_gdf = core.edge_gdf_from_graph(self.G)
+        assert edge_gdf.shape[0] == 2
+        assert isinstance(edge_gdf, gpd.GeoDataFrame)
+        assert "stnode" in edge_gdf.columns
+        assert "endnode" in edge_gdf.columns
+        assert "geometry" in edge_gdf.columns
+
+    # def test_graph_nodes_intersecting_polgyon(self):
+    #     """Test the graph_nodes_intersecting_polygon function."""
+    #     # call function
+    #     int_list = core.graph_nodes_intersecting_polygon(self.G, self.poly_gdf)
+    #     import pdb
+
+    #     pdb.set_trace()
+
+    # def test_graph_edges_intersecting_polgyon(self):
+    #     """Test the graph_edges_intersecting_polygon function."""
+    #     int_list = core.graph_edges_intersecting_polygon(
+    #         self.G, self.poly_gdf, mode="contains"
+    #     )
 
 
 def test_sample_raster():