Add Pytest and tests for dsu (#5)

.github/workflows/python-package.yml

@@ -34,6 +34,6 @@ jobs:
         flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
         # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
         flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
-    # - name: Test with pytest
-    #   run: |
-    #     pytest
+    - name: Test with pytest
+      run: |
+        pytest

tests/test_dsu.py

@@ -0,0 +1,209 @@
+import pytest
+
+from atcoder.dsu import DSU
+
+
+@pytest.fixture
+def dsu():
+    return DSU(5)
+
+
+class TestDsu:
+
+    def test_initial_status(self, dsu):
+        '''
+        An initialized dsu object is expected to be independent of all
+        vertices.
+
+        GIVEN an initialized dsu object
+        WHEN before executing dsu.merge(vertex a, vertex b)
+        THEN all the vertices are independent
+        '''
+
+        pair_of_vertices = self._generate_pair_of_vertices()
+
+        for first_vertex, second_vertex in pair_of_vertices:
+            is_same = dsu.same(first_vertex, second_vertex)
+            assert not is_same
+
+        for index in range(5):
+            assert dsu.size(index) == 1
+            assert dsu.leader(index) == index
+
+        assert dsu.groups() == [[0], [1], [2], [3], [4]]
+
+    def _generate_pair_of_vertices(self):
+        from itertools import combinations
+
+        return list(combinations(range(5), 2))
+
+    def test_merge(self, dsu):
+        '''
+        dsu.merge(vertex a, vertex b) is expected to be in the same group.
+
+        GIVEN an initialized dsu object
+        WHEN vertex 0 and 1 are merged
+        THEN vertex 0 and 1 are the same group.
+        '''
+
+        is_same = dsu.same(0, 1)
+        assert not is_same
+
+        dsu.merge(0, 1)
+        is_same = dsu.same(0, 1)
+        assert is_same
+
+    def test_merge_elements_of_same_group(self, dsu):
+        '''
+        merge elements of the same group.
+
+        GIVEN an initialized dsu object
+        WHEN merge vertex 0 and 1 twice
+        THEN vertex 0 and 1 are the same group. Their size is 2.
+        '''
+
+        is_same = dsu.same(0, 1)
+        assert not is_same
+
+        for _ in range(2):
+            dsu.merge(0, 1)
+            is_same = dsu.same(0, 1)
+            assert is_same
+            assert dsu.size(0) == 2
+            assert dsu.size(1) == 2
+
+    def test_size(self, dsu):
+        '''
+        dsu.size(vertex a) is expected to get size of vertex a.
+
+        GIVEN an initialized dsu object
+        WHEN vertex 0, 1 and 2 are merged
+        THEN size of vertex 0 is 3.
+        '''
+
+        dsu.merge(0, 1)
+        dsu.merge(0, 2)
+        assert dsu.size(0) == 3
+
+    def test_leader(self, dsu):
+        '''
+        dsu.leader(vertex a) is expected to return the representative of the
+        connected component that contains the vertex a.
+
+        GIVEN an initialized dsu object
+        WHEN vertex 0, 1 and 2 are merged
+        THEN vertex 1 and 2 belong to any of the vertices 0-2.
+        '''
+
+        dsu.merge(0, 1)
+        dsu.merge(0, 2)
+
+        assert dsu.leader(1) in [0, 1, 2]
+        assert dsu.leader(2) in [0, 1, 2]
+        assert dsu.leader(3) not in [0, 1, 2]
+        assert dsu.leader(4) not in [0, 1, 2]
+
+    def test_groups(self, dsu):
+        '''
+        dsu.groups() is expected to return the list of the graph that divided
+        into connected components.
+
+        GIVEN an initialized dsu object
+        WHEN vertex 0, 1 and 2 are merged
+        THEN returns [[0, 1, 2], [3], [4]]
+        '''
+
+        dsu.merge(0, 1)
+        dsu.merge(0, 2)
+
+        assert dsu.groups() == [[0, 1, 2], [3], [4]]
+
+    @pytest.mark.parametrize((
+        'vertex_a', 'vertex_b'
+        ), [
+        (-2, 4),
+        (-1, 4),
+        (0, 5),
+        (0, 6),
+        (-1, 5),
+        (-1, 6),
+    ])
+    def test_merge_failed_if_invalid_input_is_given(self, dsu,
+                                                    vertex_a, vertex_b):
+        '''
+        dsu.merge(vertex a, vertex b) is expected to be raised an
+        AssertionError if an invalid input is given.
+
+        GIVEN an initialized dsu object
+        WHEN an out-of-range index is given
+        THEN raises an AssertionError
+        '''
+
+        with pytest.raises(AssertionError):
+            dsu.merge(vertex_a, vertex_b)
+
+    @pytest.mark.parametrize((
+        'vertex_a', 'vertex_b'
+        ), [
+        (-2, 4),
+        (-1, 4),
+        (0, 5),
+        (0, 6),
+        (-1, 5),
+        (-1, 6),
+    ])
+    def test_same_failed_if_invalid_input_is_given(self, dsu,
+                                                   vertex_a, vertex_b):
+        '''
+        dsu.same(vertex a, vertex b) is expected to be raised an AssertionError
+        if an invalid input is given.
+
+        GIVEN an initialized dsu object
+        WHEN an out-of-range index is given
+        THEN raises an AssertionError
+        '''
+
+        with pytest.raises(AssertionError):
+            dsu.same(vertex_a, vertex_b)
+
+    @pytest.mark.parametrize((
+        'vertex_a'
+        ), [
+        -2,
+        -1,
+        5,
+        6,
+    ])
+    def test_leader_failed_if_invalid_input_is_given(self, dsu, vertex_a):
+        '''
+        dsu.leader(vertex a) is expected to be raised an AssertionError if an
+        invalid input is given.
+
+        GIVEN an initialized dsu object
+        WHEN an out-of-range index is given
+        THEN raises an AssertionError
+        '''
+
+        with pytest.raises(AssertionError):
+            dsu.leader(vertex_a)
+
+    @pytest.mark.parametrize((
+        'vertex_a'
+        ), [
+        -2,
+        -1,
+        5,
+        6,
+    ])
+    def test_size_failed_if_invalid_input_is_given(self, dsu, vertex_a):
+        '''
+        dsu.size(vertex a) is expected to be raised an AssertionError if an
+        invalid input is given.
+
+        GIVEN an initialized dsu object
+        WHEN an out-of-range index is given
+        THEN raises an AssertionError
+        '''
+
+        with pytest.raises(AssertionError):
+            dsu.size(vertex_a)