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75 lines
2.8 KiB
Python
75 lines
2.8 KiB
Python
"""Tests for shortest-path."""
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import pytest
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from solution import shortest_path
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class TestBasicCases:
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"""Test basic functionality with typical inputs."""
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def test_example_one(self):
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"""Test first example from problem description."""
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edges = [("A", "B", 4), ("A", "C", 2), ("C", "B", 1), ("B", "D", 5), ("C", "D", 8)]
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assert shortest_path(edges, "A", "D") == (7, ["A", "C", "B", "D"])
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def test_example_two(self):
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"""Test second example with no reverse path."""
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edges = [("X", "Y", 3)]
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assert shortest_path(edges, "Y", "X") == (-1, [])
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def test_example_three(self):
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"""Test indirect path cheaper than direct edge."""
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edges = [("A", "B", 1), ("B", "C", 2), ("A", "C", 10)]
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assert shortest_path(edges, "A", "C") == (3, ["A", "B", "C"])
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def test_direct_edge_is_shortest(self):
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"""Test when the direct edge is the cheapest route."""
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edges = [("A", "B", 1), ("A", "C", 5), ("C", "B", 5)]
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assert shortest_path(edges, "A", "B") == (1, ["A", "B"])
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class TestEdgeCases:
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"""Test edge cases and boundary conditions."""
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def test_start_equals_end(self):
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"""Test when start and end are the same node."""
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edges = [("A", "B", 1)]
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assert shortest_path(edges, "A", "A") == (0, ["A"])
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def test_no_edges(self):
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"""Test with empty edge list and different start/end."""
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assert shortest_path([], "A", "B") == (-1, [])
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def test_single_edge_path(self):
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"""Test path that is a single edge."""
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edges = [("A", "B", 7)]
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assert shortest_path(edges, "A", "B") == (7, ["A", "B"])
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def test_long_chain(self):
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"""Test shortest path through a long chain of nodes."""
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edges = [("A", "B", 1), ("B", "C", 1), ("C", "D", 1), ("D", "E", 1)]
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assert shortest_path(edges, "A", "E") == (4, ["A", "B", "C", "D", "E"])
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def test_disconnected_graph(self):
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"""Test with disconnected components."""
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edges = [("A", "B", 1), ("C", "D", 1)]
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assert shortest_path(edges, "A", "D") == (-1, [])
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def test_multiple_paths_picks_cheapest(self):
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"""Test graph with many paths to verify optimal is chosen."""
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edges = [
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("S", "A", 10), ("S", "B", 3), ("B", "A", 1),
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("A", "T", 2), ("B", "T", 20),
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]
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cost, path = shortest_path(edges, "S", "T")
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assert cost == 6
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assert path[0] == "S" and path[-1] == "T"
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def test_large_weights(self):
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"""Test with large edge weights."""
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edges = [("A", "B", 1000000), ("B", "C", 1000000)]
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assert shortest_path(edges, "A", "C") == (2000000, ["A", "B", "C"])
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def test_end_node_not_in_graph(self):
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"""Test when end node has no edges at all."""
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edges = [("A", "B", 1), ("B", "C", 2)]
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assert shortest_path(edges, "A", "Z") == (-1, [])
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