Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/networkx/algorithms/components/tests/test_attracting.py

@@ -0,0 +1,68 @@
+import pytest
+import networkx as nx
+from networkx import NetworkXNotImplemented
+
+
+class TestAttractingComponents:
+    @classmethod
+    def setup_class(cls):
+        cls.G1 = nx.DiGraph()
+        cls.G1.add_edges_from(
+            [
+                (5, 11),
+                (11, 2),
+                (11, 9),
+                (11, 10),
+                (7, 11),
+                (7, 8),
+                (8, 9),
+                (3, 8),
+                (3, 10),
+            ]
+        )
+        cls.G2 = nx.DiGraph()
+        cls.G2.add_edges_from([(0, 1), (0, 2), (1, 1), (1, 2), (2, 1)])
+
+        cls.G3 = nx.DiGraph()
+        cls.G3.add_edges_from([(0, 1), (1, 2), (2, 1), (0, 3), (3, 4), (4, 3)])
+
+        cls.G4 = nx.DiGraph()
+
+    def test_attracting_components(self):
+        ac = list(nx.attracting_components(self.G1))
+        assert {2} in ac
+        assert {9} in ac
+        assert {10} in ac
+
+        ac = list(nx.attracting_components(self.G2))
+        ac = [tuple(sorted(x)) for x in ac]
+        assert ac == [(1, 2)]
+
+        ac = list(nx.attracting_components(self.G3))
+        ac = [tuple(sorted(x)) for x in ac]
+        assert (1, 2) in ac
+        assert (3, 4) in ac
+        assert len(ac) == 2
+
+        ac = list(nx.attracting_components(self.G4))
+        assert ac == []
+
+    def test_number_attacting_components(self):
+        assert nx.number_attracting_components(self.G1) == 3
+        assert nx.number_attracting_components(self.G2) == 1
+        assert nx.number_attracting_components(self.G3) == 2
+        assert nx.number_attracting_components(self.G4) == 0
+
+    def test_is_attracting_component(self):
+        assert not nx.is_attracting_component(self.G1)
+        assert not nx.is_attracting_component(self.G2)
+        assert not nx.is_attracting_component(self.G3)
+        g2 = self.G3.subgraph([1, 2])
+        assert nx.is_attracting_component(g2)
+        assert not nx.is_attracting_component(self.G4)
+
+    def test_connected_raise(self):
+        G = nx.Graph()
+        pytest.raises(NetworkXNotImplemented, nx.attracting_components, G)
+        pytest.raises(NetworkXNotImplemented, nx.number_attracting_components, G)
+        pytest.raises(NetworkXNotImplemented, nx.is_attracting_component, G)

venv/Lib/site-packages/networkx/algorithms/components/tests/test_biconnected.py

@@ -0,0 +1,244 @@
+import pytest
+import networkx as nx
+from networkx import NetworkXNotImplemented
+
+
+def assert_components_edges_equal(x, y):
+    sx = {frozenset([frozenset(e) for e in c]) for c in x}
+    sy = {frozenset([frozenset(e) for e in c]) for c in y}
+    assert sx == sy
+
+
+def assert_components_equal(x, y):
+    sx = {frozenset(c) for c in x}
+    sy = {frozenset(c) for c in y}
+    assert sx == sy
+
+
+def test_barbell():
+    G = nx.barbell_graph(8, 4)
+    nx.add_path(G, [7, 20, 21, 22])
+    nx.add_cycle(G, [22, 23, 24, 25])
+    pts = set(nx.articulation_points(G))
+    assert pts == {7, 8, 9, 10, 11, 12, 20, 21, 22}
+
+    answer = [
+        {12, 13, 14, 15, 16, 17, 18, 19},
+        {0, 1, 2, 3, 4, 5, 6, 7},
+        {22, 23, 24, 25},
+        {11, 12},
+        {10, 11},
+        {9, 10},
+        {8, 9},
+        {7, 8},
+        {21, 22},
+        {20, 21},
+        {7, 20},
+    ]
+    assert_components_equal(list(nx.biconnected_components(G)), answer)
+
+    G.add_edge(2, 17)
+    pts = set(nx.articulation_points(G))
+    assert pts == {7, 20, 21, 22}
+
+
+def test_articulation_points_repetitions():
+    G = nx.Graph()
+    G.add_edges_from([(0, 1), (1, 2), (1, 3)])
+    assert list(nx.articulation_points(G)) == [1]
+
+
+def test_articulation_points_cycle():
+    G = nx.cycle_graph(3)
+    nx.add_cycle(G, [1, 3, 4])
+    pts = set(nx.articulation_points(G))
+    assert pts == {1}
+
+
+def test_is_biconnected():
+    G = nx.cycle_graph(3)
+    assert nx.is_biconnected(G)
+    nx.add_cycle(G, [1, 3, 4])
+    assert not nx.is_biconnected(G)
+
+
+def test_empty_is_biconnected():
+    G = nx.empty_graph(5)
+    assert not nx.is_biconnected(G)
+    G.add_edge(0, 1)
+    assert not nx.is_biconnected(G)
+
+
+def test_biconnected_components_cycle():
+    G = nx.cycle_graph(3)
+    nx.add_cycle(G, [1, 3, 4])
+    answer = [{0, 1, 2}, {1, 3, 4}]
+    assert_components_equal(list(nx.biconnected_components(G)), answer)
+
+
+def test_biconnected_components1():
+    # graph example from
+    # http://www.ibluemojo.com/school/articul_algorithm.html
+    edges = [
+        (0, 1),
+        (0, 5),
+        (0, 6),
+        (0, 14),
+        (1, 5),
+        (1, 6),
+        (1, 14),
+        (2, 4),
+        (2, 10),
+        (3, 4),
+        (3, 15),
+        (4, 6),
+        (4, 7),
+        (4, 10),
+        (5, 14),
+        (6, 14),
+        (7, 9),
+        (8, 9),
+        (8, 12),
+        (8, 13),
+        (10, 15),
+        (11, 12),
+        (11, 13),
+        (12, 13),
+    ]
+    G = nx.Graph(edges)
+    pts = set(nx.articulation_points(G))
+    assert pts == {4, 6, 7, 8, 9}
+    comps = list(nx.biconnected_component_edges(G))
+    answer = [
+        [(3, 4), (15, 3), (10, 15), (10, 4), (2, 10), (4, 2)],
+        [(13, 12), (13, 8), (11, 13), (12, 11), (8, 12)],
+        [(9, 8)],
+        [(7, 9)],
+        [(4, 7)],
+        [(6, 4)],
+        [(14, 0), (5, 1), (5, 0), (14, 5), (14, 1), (6, 14), (6, 0), (1, 6), (0, 1)],
+    ]
+    assert_components_edges_equal(comps, answer)
+
+
+def test_biconnected_components2():
+    G = nx.Graph()
+    nx.add_cycle(G, "ABC")
+    nx.add_cycle(G, "CDE")
+    nx.add_cycle(G, "FIJHG")
+    nx.add_cycle(G, "GIJ")
+    G.add_edge("E", "G")
+    comps = list(nx.biconnected_component_edges(G))
+    answer = [
+        [
+            tuple("GF"),
+            tuple("FI"),
+            tuple("IG"),
+            tuple("IJ"),
+            tuple("JG"),
+            tuple("JH"),
+            tuple("HG"),
+        ],
+        [tuple("EG")],
+        [tuple("CD"), tuple("DE"), tuple("CE")],
+        [tuple("AB"), tuple("BC"), tuple("AC")],
+    ]
+    assert_components_edges_equal(comps, answer)
+
+
+def test_biconnected_davis():
+    D = nx.davis_southern_women_graph()
+    bcc = list(nx.biconnected_components(D))[0]
+    assert set(D) == bcc  # All nodes in a giant bicomponent
+    # So no articulation points
+    assert len(list(nx.articulation_points(D))) == 0
+
+
+def test_biconnected_karate():
+    K = nx.karate_club_graph()
+    answer = [
+        {
+            0,
+            1,
+            2,
+            3,
+            7,
+            8,
+            9,
+            12,
+            13,
+            14,
+            15,
+            17,
+            18,
+            19,
+            20,
+            21,
+            22,
+            23,
+            24,
+            25,
+            26,
+            27,
+            28,
+            29,
+            30,
+            31,
+            32,
+            33,
+        },
+        {0, 4, 5, 6, 10, 16},
+        {0, 11},
+    ]
+    bcc = list(nx.biconnected_components(K))
+    assert_components_equal(bcc, answer)
+    assert set(nx.articulation_points(K)) == {0}
+
+
+def test_biconnected_eppstein():
+    # tests from http://www.ics.uci.edu/~eppstein/PADS/Biconnectivity.py
+    G1 = nx.Graph(
+        {
+            0: [1, 2, 5],
+            1: [0, 5],
+            2: [0, 3, 4],
+            3: [2, 4, 5, 6],
+            4: [2, 3, 5, 6],
+            5: [0, 1, 3, 4],
+            6: [3, 4],
+        }
+    )
+    G2 = nx.Graph(
+        {
+            0: [2, 5],
+            1: [3, 8],
+            2: [0, 3, 5],
+            3: [1, 2, 6, 8],
+            4: [7],
+            5: [0, 2],
+            6: [3, 8],
+            7: [4],
+            8: [1, 3, 6],
+        }
+    )
+    assert nx.is_biconnected(G1)
+    assert not nx.is_biconnected(G2)
+    answer_G2 = [{1, 3, 6, 8}, {0, 2, 5}, {2, 3}, {4, 7}]
+    bcc = list(nx.biconnected_components(G2))
+    assert_components_equal(bcc, answer_G2)
+
+
+def test_null_graph():
+    G = nx.Graph()
+    assert not nx.is_biconnected(G)
+    assert list(nx.biconnected_components(G)) == []
+    assert list(nx.biconnected_component_edges(G)) == []
+    assert list(nx.articulation_points(G)) == []
+
+
+def test_connected_raise():
+    DG = nx.DiGraph()
+    pytest.raises(NetworkXNotImplemented, nx.biconnected_components, DG)
+    pytest.raises(NetworkXNotImplemented, nx.biconnected_component_edges, DG)
+    pytest.raises(NetworkXNotImplemented, nx.articulation_points, DG)
+    pytest.raises(NetworkXNotImplemented, nx.is_biconnected, DG)

venv/Lib/site-packages/networkx/algorithms/components/tests/test_connected.py

@@ -0,0 +1,111 @@
+import pytest
+import networkx as nx
+from networkx import convert_node_labels_to_integers as cnlti
+from networkx import NetworkXNotImplemented
+
+
+class TestConnected:
+    @classmethod
+    def setup_class(cls):
+        G1 = cnlti(nx.grid_2d_graph(2, 2), first_label=0, ordering="sorted")
+        G2 = cnlti(nx.lollipop_graph(3, 3), first_label=4, ordering="sorted")
+        G3 = cnlti(nx.house_graph(), first_label=10, ordering="sorted")
+        cls.G = nx.union(G1, G2)
+        cls.G = nx.union(cls.G, G3)
+        cls.DG = nx.DiGraph([(1, 2), (1, 3), (2, 3)])
+        cls.grid = cnlti(nx.grid_2d_graph(4, 4), first_label=1)
+
+        cls.gc = []
+        G = nx.DiGraph()
+        G.add_edges_from(
+            [
+                (1, 2),
+                (2, 3),
+                (2, 8),
+                (3, 4),
+                (3, 7),
+                (4, 5),
+                (5, 3),
+                (5, 6),
+                (7, 4),
+                (7, 6),
+                (8, 1),
+                (8, 7),
+            ]
+        )
+        C = [[3, 4, 5, 7], [1, 2, 8], [6]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        G.add_edges_from([(1, 2), (1, 3), (1, 4), (4, 2), (3, 4), (2, 3)])
+        C = [[2, 3, 4], [1]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        G.add_edges_from([(1, 2), (2, 3), (3, 2), (2, 1)])
+        C = [[1, 2, 3]]
+        cls.gc.append((G, C))
+
+        # Eppstein's tests
+        G = nx.DiGraph({0: [1], 1: [2, 3], 2: [4, 5], 3: [4, 5], 4: [6], 5: [], 6: []})
+        C = [[0], [1], [2], [3], [4], [5], [6]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph({0: [1], 1: [2, 3, 4], 2: [0, 3], 3: [4], 4: [3]})
+        C = [[0, 1, 2], [3, 4]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        C = []
+        cls.gc.append((G, C))
+
+    def test_connected_components(self):
+        cc = nx.connected_components
+        G = self.G
+        C = {
+            frozenset([0, 1, 2, 3]),
+            frozenset([4, 5, 6, 7, 8, 9]),
+            frozenset([10, 11, 12, 13, 14]),
+        }
+        assert {frozenset(g) for g in cc(G)} == C
+
+    def test_number_connected_components(self):
+        ncc = nx.number_connected_components
+        assert ncc(self.G) == 3
+
+    def test_number_connected_components2(self):
+        ncc = nx.number_connected_components
+        assert ncc(self.grid) == 1
+
+    def test_connected_components2(self):
+        cc = nx.connected_components
+        G = self.grid
+        C = {frozenset([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16])}
+        assert {frozenset(g) for g in cc(G)} == C
+
+    def test_node_connected_components(self):
+        ncc = nx.node_connected_component
+        G = self.grid
+        C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
+        assert ncc(G, 1) == C
+
+    def test_is_connected(self):
+        assert nx.is_connected(self.grid)
+        G = nx.Graph()
+        G.add_nodes_from([1, 2])
+        assert not nx.is_connected(G)
+
+    def test_connected_raise(self):
+        pytest.raises(NetworkXNotImplemented, nx.connected_components, self.DG)
+        pytest.raises(NetworkXNotImplemented, nx.number_connected_components, self.DG)
+        pytest.raises(NetworkXNotImplemented, nx.node_connected_component, self.DG, 1)
+        pytest.raises(NetworkXNotImplemented, nx.is_connected, self.DG)
+        pytest.raises(nx.NetworkXPointlessConcept, nx.is_connected, nx.Graph())
+
+    def test_connected_mutability(self):
+        G = self.grid
+        seen = set()
+        for component in nx.connected_components(G):
+            assert len(seen & component) == 0
+            seen.update(component)
+            component.clear()

venv/Lib/site-packages/networkx/algorithms/components/tests/test_semiconnected.py

@@ -0,0 +1,53 @@
+from itertools import chain
+import networkx as nx
+import pytest
+
+
+class TestIsSemiconnected:
+    def test_undirected(self):
+        pytest.raises(nx.NetworkXNotImplemented, nx.is_semiconnected, nx.Graph())
+        pytest.raises(nx.NetworkXNotImplemented, nx.is_semiconnected, nx.MultiGraph())
+
+    def test_empty(self):
+        pytest.raises(nx.NetworkXPointlessConcept, nx.is_semiconnected, nx.DiGraph())
+        pytest.raises(
+            nx.NetworkXPointlessConcept, nx.is_semiconnected, nx.MultiDiGraph()
+        )
+
+    def test_single_node_graph(self):
+        G = nx.DiGraph()
+        G.add_node(0)
+        assert nx.is_semiconnected(G)
+
+    def test_path(self):
+        G = nx.path_graph(100, create_using=nx.DiGraph())
+        assert nx.is_semiconnected(G)
+        G.add_edge(100, 99)
+        assert not nx.is_semiconnected(G)
+
+    def test_cycle(self):
+        G = nx.cycle_graph(100, create_using=nx.DiGraph())
+        assert nx.is_semiconnected(G)
+        G = nx.path_graph(100, create_using=nx.DiGraph())
+        G.add_edge(0, 99)
+        assert nx.is_semiconnected(G)
+
+    def test_tree(self):
+        G = nx.DiGraph()
+        G.add_edges_from(
+            chain.from_iterable([(i, 2 * i + 1), (i, 2 * i + 2)] for i in range(100))
+        )
+        assert not nx.is_semiconnected(G)
+
+    def test_dumbbell(self):
+        G = nx.cycle_graph(100, create_using=nx.DiGraph())
+        G.add_edges_from((i + 100, (i + 1) % 100 + 100) for i in range(100))
+        assert not nx.is_semiconnected(G)  # G is disconnected.
+        G.add_edge(100, 99)
+        assert nx.is_semiconnected(G)
+
+    def test_alternating_path(self):
+        G = nx.DiGraph(
+            chain.from_iterable([(i, i - 1), (i, i + 1)] for i in range(0, 100, 2))
+        )
+        assert not nx.is_semiconnected(G)

venv/Lib/site-packages/networkx/algorithms/components/tests/test_strongly_connected.py

@@ -0,0 +1,216 @@
+import pytest
+import networkx as nx
+from networkx import NetworkXNotImplemented
+
+
+class TestStronglyConnected:
+    @classmethod
+    def setup_class(cls):
+        cls.gc = []
+        G = nx.DiGraph()
+        G.add_edges_from(
+            [
+                (1, 2),
+                (2, 3),
+                (2, 8),
+                (3, 4),
+                (3, 7),
+                (4, 5),
+                (5, 3),
+                (5, 6),
+                (7, 4),
+                (7, 6),
+                (8, 1),
+                (8, 7),
+            ]
+        )
+        C = {frozenset([3, 4, 5, 7]), frozenset([1, 2, 8]), frozenset([6])}
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        G.add_edges_from([(1, 2), (1, 3), (1, 4), (4, 2), (3, 4), (2, 3)])
+        C = {frozenset([2, 3, 4]), frozenset([1])}
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        G.add_edges_from([(1, 2), (2, 3), (3, 2), (2, 1)])
+        C = {frozenset([1, 2, 3])}
+        cls.gc.append((G, C))
+
+        # Eppstein's tests
+        G = nx.DiGraph({0: [1], 1: [2, 3], 2: [4, 5], 3: [4, 5], 4: [6], 5: [], 6: []})
+        C = {
+            frozenset([0]),
+            frozenset([1]),
+            frozenset([2]),
+            frozenset([3]),
+            frozenset([4]),
+            frozenset([5]),
+            frozenset([6]),
+        }
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph({0: [1], 1: [2, 3, 4], 2: [0, 3], 3: [4], 4: [3]})
+        C = {frozenset([0, 1, 2]), frozenset([3, 4])}
+        cls.gc.append((G, C))
+
+    def test_tarjan(self):
+        scc = nx.strongly_connected_components
+        for G, C in self.gc:
+            assert {frozenset(g) for g in scc(G)} == C
+
+    def test_tarjan_recursive(self):
+        scc = nx.strongly_connected_components_recursive
+        for G, C in self.gc:
+            assert {frozenset(g) for g in scc(G)} == C
+
+    def test_kosaraju(self):
+        scc = nx.kosaraju_strongly_connected_components
+        for G, C in self.gc:
+            assert {frozenset(g) for g in scc(G)} == C
+
+    def test_number_strongly_connected_components(self):
+        ncc = nx.number_strongly_connected_components
+        for G, C in self.gc:
+            assert ncc(G) == len(C)
+
+    def test_is_strongly_connected(self):
+        for G, C in self.gc:
+            if len(C) == 1:
+                assert nx.is_strongly_connected(G)
+            else:
+                assert not nx.is_strongly_connected(G)
+
+    def test_contract_scc1(self):
+        G = nx.DiGraph()
+        G.add_edges_from(
+            [
+                (1, 2),
+                (2, 3),
+                (2, 11),
+                (2, 12),
+                (3, 4),
+                (4, 3),
+                (4, 5),
+                (5, 6),
+                (6, 5),
+                (6, 7),
+                (7, 8),
+                (7, 9),
+                (7, 10),
+                (8, 9),
+                (9, 7),
+                (10, 6),
+                (11, 2),
+                (11, 4),
+                (11, 6),
+                (12, 6),
+                (12, 11),
+            ]
+        )
+        scc = list(nx.strongly_connected_components(G))
+        cG = nx.condensation(G, scc)
+        # DAG
+        assert nx.is_directed_acyclic_graph(cG)
+        # nodes
+        assert sorted(cG.nodes()) == [0, 1, 2, 3]
+        # edges
+        mapping = {}
+        for i, component in enumerate(scc):
+            for n in component:
+                mapping[n] = i
+        edge = (mapping[2], mapping[3])
+        assert cG.has_edge(*edge)
+        edge = (mapping[2], mapping[5])
+        assert cG.has_edge(*edge)
+        edge = (mapping[3], mapping[5])
+        assert cG.has_edge(*edge)
+
+    def test_contract_scc_isolate(self):
+        # Bug found and fixed in [1687].
+        G = nx.DiGraph()
+        G.add_edge(1, 2)
+        G.add_edge(2, 1)
+        scc = list(nx.strongly_connected_components(G))
+        cG = nx.condensation(G, scc)
+        assert list(cG.nodes()) == [0]
+        assert list(cG.edges()) == []
+
+    def test_contract_scc_edge(self):
+        G = nx.DiGraph()
+        G.add_edge(1, 2)
+        G.add_edge(2, 1)
+        G.add_edge(2, 3)
+        G.add_edge(3, 4)
+        G.add_edge(4, 3)
+        scc = list(nx.strongly_connected_components(G))
+        cG = nx.condensation(G, scc)
+        assert sorted(cG.nodes()) == [0, 1]
+        if 1 in scc[0]:
+            edge = (0, 1)
+        else:
+            edge = (1, 0)
+        assert list(cG.edges()) == [edge]
+
+    def test_condensation_mapping_and_members(self):
+        G, C = self.gc[1]
+        C = sorted(C, key=len, reverse=True)
+        cG = nx.condensation(G)
+        mapping = cG.graph["mapping"]
+        assert all(n in G for n in mapping)
+        assert all(0 == cN for n, cN in mapping.items() if n in C[0])
+        assert all(1 == cN for n, cN in mapping.items() if n in C[1])
+        for n, d in cG.nodes(data=True):
+            assert set(C[n]) == cG.nodes[n]["members"]
+
+    def test_null_graph(self):
+        G = nx.DiGraph()
+        assert list(nx.strongly_connected_components(G)) == []
+        assert list(nx.kosaraju_strongly_connected_components(G)) == []
+        assert list(nx.strongly_connected_components_recursive(G)) == []
+        assert len(nx.condensation(G)) == 0
+        pytest.raises(
+            nx.NetworkXPointlessConcept, nx.is_strongly_connected, nx.DiGraph()
+        )
+
+    def test_connected_raise(self):
+        G = nx.Graph()
+        pytest.raises(NetworkXNotImplemented, nx.strongly_connected_components, G)
+        pytest.raises(
+            NetworkXNotImplemented, nx.kosaraju_strongly_connected_components, G
+        )
+        pytest.raises(
+            NetworkXNotImplemented, nx.strongly_connected_components_recursive, G
+        )
+        pytest.raises(NetworkXNotImplemented, nx.is_strongly_connected, G)
+        pytest.raises(
+            nx.NetworkXPointlessConcept, nx.is_strongly_connected, nx.DiGraph()
+        )
+        pytest.raises(NetworkXNotImplemented, nx.condensation, G)
+
+
+#    Commented out due to variability on Travis-CI hardware/operating systems
+#    def test_linear_time(self):
+#        # See Issue #2831
+#        count = 100  # base case
+#        dg = nx.DiGraph()
+#        dg.add_nodes_from([0, 1])
+#        for i in range(2, count):
+#            dg.add_node(i)
+#            dg.add_edge(i, 1)
+#            dg.add_edge(0, i)
+#        t = time.time()
+#        ret = tuple(nx.strongly_connected_components(dg))
+#        dt = time.time() - t
+#
+#        count = 200
+#        dg = nx.DiGraph()
+#        dg.add_nodes_from([0, 1])
+#        for i in range(2, count):
+#            dg.add_node(i)
+#            dg.add_edge(i, 1)
+#            dg.add_edge(0, i)
+#        t = time.time()
+#        ret = tuple(nx.strongly_connected_components(dg))
+#        dt2 = time.time() - t
+#        assert_less(dt2, dt * 2.3)  # should be 2 times longer for this graph

venv/Lib/site-packages/networkx/algorithms/components/tests/test_weakly_connected.py

@@ -0,0 +1,78 @@
+import pytest
+import networkx as nx
+from networkx import NetworkXNotImplemented
+
+
+class TestWeaklyConnected:
+    @classmethod
+    def setup_class(cls):
+        cls.gc = []
+        G = nx.DiGraph()
+        G.add_edges_from(
+            [
+                (1, 2),
+                (2, 3),
+                (2, 8),
+                (3, 4),
+                (3, 7),
+                (4, 5),
+                (5, 3),
+                (5, 6),
+                (7, 4),
+                (7, 6),
+                (8, 1),
+                (8, 7),
+            ]
+        )
+        C = [[3, 4, 5, 7], [1, 2, 8], [6]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        G.add_edges_from([(1, 2), (1, 3), (1, 4), (4, 2), (3, 4), (2, 3)])
+        C = [[2, 3, 4], [1]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph()
+        G.add_edges_from([(1, 2), (2, 3), (3, 2), (2, 1)])
+        C = [[1, 2, 3]]
+        cls.gc.append((G, C))
+
+        # Eppstein's tests
+        G = nx.DiGraph({0: [1], 1: [2, 3], 2: [4, 5], 3: [4, 5], 4: [6], 5: [], 6: []})
+        C = [[0], [1], [2], [3], [4], [5], [6]]
+        cls.gc.append((G, C))
+
+        G = nx.DiGraph({0: [1], 1: [2, 3, 4], 2: [0, 3], 3: [4], 4: [3]})
+        C = [[0, 1, 2], [3, 4]]
+        cls.gc.append((G, C))
+
+    def test_weakly_connected_components(self):
+        for G, C in self.gc:
+            U = G.to_undirected()
+            w = {frozenset(g) for g in nx.weakly_connected_components(G)}
+            c = {frozenset(g) for g in nx.connected_components(U)}
+            assert w == c
+
+    def test_number_weakly_connected_components(self):
+        for G, C in self.gc:
+            U = G.to_undirected()
+            w = nx.number_weakly_connected_components(G)
+            c = nx.number_connected_components(U)
+            assert w == c
+
+    def test_is_weakly_connected(self):
+        for G, C in self.gc:
+            U = G.to_undirected()
+            assert nx.is_weakly_connected(G) == nx.is_connected(U)
+
+    def test_null_graph(self):
+        G = nx.DiGraph()
+        assert list(nx.weakly_connected_components(G)) == []
+        assert nx.number_weakly_connected_components(G) == 0
+        pytest.raises(nx.NetworkXPointlessConcept, nx.is_weakly_connected, G)
+
+    def test_connected_raise(self):
+        G = nx.Graph()
+        pytest.raises(NetworkXNotImplemented, nx.weakly_connected_components, G)
+        pytest.raises(NetworkXNotImplemented, nx.number_weakly_connected_components, G)
+        pytest.raises(NetworkXNotImplemented, nx.is_weakly_connected, G)