Cover matcher and API scenarios

tests/test_normalization.py

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+from __future__ import annotations
+
+import pytest
+
+from app.aliases import ProductAliasIndex
+from app.normalization import normalize_text
+from app.typo import damerau_levenshtein_distance, word_similarity
+
+
+@pytest.mark.parametrize(
+    ("source", "expected"),
+    [
+        ("Шуруповёрт", "шуруповерт"),
+        ("3,5 × 25", "3.5x25"),
+        ("4.2 х 75", "4.2x75"),
+        ("М10", "m10"),
+        ("Р120", "p120"),
+    ],
+)
+def test_basic_canonicalization(source: str, expected: str) -> None:
+    assert normalize_text(source) == expected
+
+
+def test_cyrillic_x_is_not_replaced_inside_words() -> None:
+    assert normalize_text("хомут находится") == "хомут находится"
+
+
+def test_damerau_counts_adjacent_transposition_as_one_edit() -> None:
+    assert damerau_levenshtein_distance("шуруповерт", "шурпуоверт") == 1
+
+
+def test_heavily_damaged_product_word_still_has_useful_score() -> None:
+    assert word_similarity("шураывваверт", "шуруповерт") > 0.53
+
+
+@pytest.mark.parametrize(
+    ("query", "canonical"),
+    [
+        ("болгарка на 230", "ушм"),
+        ("шурик на 12в", "шуруповерт"),
+        ("пластиковые хомуты 4.8х400", "стяжка"),
+        ("шурпуоверт", "шуруповерт"),
+        ("шураыввавёрт", "шуруповерт"),
+    ],
+)
+def test_alias_and_typo_detection(query: str, canonical: str) -> None:
+    match = ProductAliasIndex().detect(query)
+    assert match is not None
+    assert match.canonical == canonical