75 lines
2.6 KiB
Python
75 lines
2.6 KiB
Python
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import networkx as nx
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from networkx.generators.trees import NIL
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from networkx.utils import arbitrary_element
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class TestPrefixTree(object):
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"""Unit tests for the prefix tree generator function."""
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def test_basic(self):
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# This example is from the Wikipedia article "Trie"
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# <https://en.wikipedia.org/wiki/Trie>.
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strings = ['a', 'to', 'tea', 'ted', 'ten', 'i', 'in', 'inn']
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T, root = nx.prefix_tree(strings)
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def source_label(v): return T.nodes[v]['source']
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# First, we check that the tree has the expected
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# structure. Recall that each node that corresponds to one of
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# the input strings has an edge to the NIL node.
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#
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# Consider the three children at level 1 in the trie.
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a, i, t = sorted(T[root], key=source_label)
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# Check the 'a' branch.
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assert len(T[a]) == 1
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nil = arbitrary_element(T[a])
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assert len(T[nil]) == 0
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# Check the 'i' branch.
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assert len(T[i]) == 2
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nil, in_ = sorted(T[i], key=source_label)
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assert len(T[nil]) == 0
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assert len(T[in_]) == 2
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nil, inn = sorted(T[in_], key=source_label)
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assert len(T[nil]) == 0
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assert len(T[inn]) == 1
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nil = arbitrary_element(T[inn])
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assert len(T[nil]) == 0
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# Check the 't' branch.
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te, to = sorted(T[t], key=source_label)
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assert len(T[to]) == 1
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nil = arbitrary_element(T[to])
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assert len(T[nil]) == 0
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tea, ted, ten = sorted(T[te], key=source_label)
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assert len(T[tea]) == 1
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assert len(T[ted]) == 1
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assert len(T[ten]) == 1
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nil = arbitrary_element(T[tea])
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assert len(T[nil]) == 0
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nil = arbitrary_element(T[ted])
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assert len(T[nil]) == 0
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nil = arbitrary_element(T[ten])
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assert len(T[nil]) == 0
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# Next, we check that the "sources" of each of the nodes is the
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# rightmost letter in the string corresponding to the path to
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# that node.
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assert source_label(root) == None
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assert source_label(a) == 'a'
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assert source_label(i) == 'i'
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assert source_label(t) == 't'
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assert source_label(in_) == 'n'
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assert source_label(inn) == 'n'
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assert source_label(to) == 'o'
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assert source_label(te) == 'e'
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assert source_label(tea) == 'a'
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assert source_label(ted) == 'd'
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assert source_label(ten) == 'n'
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assert source_label(NIL) == NIL
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def test_random_tree():
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"""Tests that a random tree is in fact a tree."""
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T = nx.random_tree(10, seed=1234)
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assert nx.is_tree(T)
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