diff --git a/causy/graph.py b/causy/graph.py
index bd010bc..bb27d29 100644
--- a/causy/graph.py
+++ b/causy/graph.py
@@ -86,6 +86,29 @@ def add_edge(self, u: Node, v: Node, value: Dict):
         self.edge_history[(u.id, v.id)] = []
         self.edge_history[(v.id, u.id)] = []
 
+    def add_directed_edge(self, u: Node, v: Node, value: Dict):
+        """
+        Add a directed edge from u to v to the graph
+        :param u: u node
+        :param v: v node
+        :return:
+        """
+
+        if u.id not in self.nodes:
+            raise GraphError(f"Node {u} does not exist")
+        if v.id not in self.nodes:
+            raise GraphError(f"Node {v} does not exist")
+
+        if u.id == v.id:
+            raise GraphError("Self loops are currently not allowed")
+
+        if u.id not in self.edges:
+            self.edges[u.id] = {}
+
+        self.edges[u.id][v.id] = value
+
+        self.edge_history[(u.id, v.id)] = []
+
     def retrieve_edge_history(
         self, u, v, action: TestResultAction = None
     ) -> List[TestResult]:
@@ -334,14 +357,28 @@ def directed_paths(self, u: Node, v: Node):
         :param v: node v
         :return: list of directed paths
         """
+        # TODO: try a better data structure for this
         if self.directed_edge_exists(u, v):
             return [[(u, v)]]
         paths = []
         for w in self.edges[u.id]:
-            for path in self.directed_paths(self.nodes[w], v):
-                paths.append([(u, w)] + path)
+            if self.directed_edge_exists(u, self.nodes[w]):
+                for path in self.directed_paths(self.nodes[w], v):
+                    paths.append([(u, self.nodes[w])] + path)
         return paths
 
+    def parents_of_node(self, u: Node):
+        """
+        Return all parents of a node u
+        :param u: node u
+        :return: list of nodes (parents)
+        """
+        parents = []
+        for w in self.edges:
+            if self.directed_edge_exists(self.nodes[w], u):
+                parents.append(self.nodes[w])
+        return parents
+
     def inducing_path_exists(self, u: Node, v: Node):
         """
         Check if an inducing path from u to v exists.
diff --git a/tests/test_graph.py b/tests/test_graph.py
index ce69977..2a4b952 100644
--- a/tests/test_graph.py
+++ b/tests/test_graph.py
@@ -50,6 +50,17 @@ def test_add_edge(self):
         self.assertEqual(graph.edge_value(node2, node1), {"test": "test"})
         self.assertTrue(graph.edge_exists(node1, node2))
 
+    def test_add_directed_edge(self):
+        graph = Graph()
+        node1 = graph.add_node("test1", [1, 2, 3])
+        node2 = graph.add_node("test2", [1, 2, 3])
+        graph.add_directed_edge(node1, node2, {"test": "test"})
+        self.assertEqual(len(graph.nodes), 2)
+        self.assertEqual(len(graph.edges), 1)
+        self.assertEqual(graph.edge_value(node1, node2), {"test": "test"})
+        self.assertTrue(graph.directed_edge_exists(node1, node2))
+        self.assertFalse(graph.directed_edge_exists(node2, node1))
+
     def test_add_edge_with_non_existing_node(self):
         graph = Graph()
         node1 = graph.add_node("test1", [1, 2, 3])
@@ -223,3 +234,37 @@ def test_undirected_edge_exists_with_non_existing_edge(self):
 
         self.assertFalse(graph.undirected_edge_exists(node1, node2))
         self.assertFalse(graph.undirected_edge_exists(node2, node1))
+
+    def test_parents_of_node_two_nodes(self):
+        graph = Graph()
+        node1 = graph.add_node("test1", [1, 2, 3])
+        node2 = graph.add_node("test2", [1, 2, 3])
+        graph.add_directed_edge(node1, node2, {"test": "test"})
+        self.assertEqual(graph.parents_of_node(node2), [node1])
+
+    def test_parents_of_node_three_nodes(self):
+        graph = Graph()
+        node1 = graph.add_node("test1", [1, 2, 3])
+        node2 = graph.add_node("test2", [1, 2, 3])
+        node3 = graph.add_node("test2", [1, 2, 3])
+        graph.add_directed_edge(node1, node2, {"test": "test"})
+        graph.add_directed_edge(node3, node2, {"test": "test"})
+        self.assertEqual(graph.parents_of_node(node2), [node1, node3])
+
+    def test_directed_paths_two_nodes(self):
+        graph = Graph()
+        node1 = graph.add_node("test1", [1, 2, 3])
+        node2 = graph.add_node("test2", [1, 2, 3])
+        graph.add_directed_edge(node1, node2, {"test": "test"})
+        self.assertEqual(graph.directed_paths(node1, node2), [[(node1, node2)]])
+
+    def test_directed_paths_three_nodes(self):
+        graph = Graph()
+        node1 = graph.add_node("test1", [1, 2, 3])
+        node2 = graph.add_node("test2", [1, 2, 3])
+        node3 = graph.add_node("test2", [1, 2, 3])
+        graph.add_directed_edge(node1, node2, {"test": "test"})
+        graph.add_directed_edge(node2, node3, {"test": "test"})
+        self.assertEqual(
+            graph.directed_paths(node1, node3), [[(node1, node2), (node2, node3)]]
+        )