Add Python bindings

reconcile-python/tests/test_reconcile.py

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+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+
+from reconcile_text import diff, reconcile, reconcile_with_history, undiff
+
+RESOURCES_DIR = Path(__file__).resolve().parent.parent.parent / "tests" / "resources"
+
+FILES = ["pride_and_prejudice.txt", "room_with_a_view.txt", "blns.txt"]
+
+
+class TestReconcile:
+    def test_basic_merge(self) -> None:
+        result = reconcile("Hello", "Hello world", "Hi world")
+        assert result["text"] == "Hi world"
+
+    def test_three_way_merge(self) -> None:
+        parent = "Merging text is hard!"
+        left = "Merging text is easy!"
+        right = "With reconcile, merging documents is hard!"
+
+        result = reconcile(parent, left, right)
+        assert result["text"] == "With reconcile, merging documents is easy!"
+
+    def test_with_cursors(self) -> None:
+        result = reconcile(
+            "Hello",
+            {"text": "Hello world", "cursors": [{"id": 3, "position": 2}]},
+            {
+                "text": "Hi world",
+                "cursors": [{"id": 4, "position": 0}, {"id": 5, "position": 3}],
+            },
+        )
+
+        assert result["text"] == "Hi world"
+        assert result["cursors"] == [
+            {"id": 3, "position": 0},
+            {"id": 4, "position": 0},
+            {"id": 5, "position": 3},
+        ]
+
+    def test_character_tokenizer(self) -> None:
+        result = reconcile("abc", "axc", "abyc", "Character")
+        assert result["text"] == "axyc"
+
+    def test_line_tokenizer(self) -> None:
+        parent = "line1\nline2\nline3\n"
+        left = "line1\nmodified\nline3\n"
+        right = "line1\nline2\nnew line\n"
+
+        result = reconcile(parent, left, right, "Line")
+        assert result["text"] == "line1\nmodified\nnew line\n"
+
+    def test_empty_texts(self) -> None:
+        result = reconcile("", "", "")
+        assert result["text"] == ""
+        assert result["cursors"] == []
+
+    def test_invalid_tokenizer(self) -> None:
+        with pytest.raises(ValueError, match="Unknown tokenizer"):
+            reconcile("a", "b", "c", "Invalid")  # type: ignore[arg-type]
+
+
+class TestReconcileWithHistory:
+    def test_returns_history(self) -> None:
+        result = reconcile_with_history(
+            "Merging text is hard!",
+            "Merging text is easy!",
+            "With reconcile, merging documents is hard!",
+        )
+
+        assert result["text"] == "With reconcile, merging documents is easy!"
+        assert len(result["history"]) > 0
+        assert all("text" in span and "history" in span for span in result["history"])
+
+    def test_history_values(self) -> None:
+        valid_histories = {
+            "Unchanged",
+            "AddedFromLeft",
+            "AddedFromRight",
+            "RemovedFromLeft",
+            "RemovedFromRight",
+        }
+        result = reconcile_with_history("Hello", "Hello world", "Hi")
+        for span in result["history"]:
+            assert span["history"] in valid_histories
+
+
+class TestDiff:
+    def test_basic_diff(self) -> None:
+        result = diff("Hello world", "Hello beautiful world")
+        assert isinstance(result, list)
+        assert all(isinstance(item, (int, str)) for item in result)
+
+    def test_no_change(self) -> None:
+        result = diff("same text", "same text")
+        # A retain-only diff
+        assert all(isinstance(item, int) and item > 0 for item in result)
+
+
+class TestUndiff:
+    def test_roundtrip(self) -> None:
+        original = "Hello world"
+        changed = "Hello beautiful world"
+
+        d = diff(original, changed)
+        reconstructed = undiff(original, d)
+        assert reconstructed == changed
+
+    def test_empty_roundtrip(self) -> None:
+        d = diff("", "")
+        assert undiff("", d) == ""
+
+    def test_invalid_diff(self) -> None:
+        with pytest.raises(ValueError):
+            undiff("short", [100])
+
+
+class TestDiffUndiffInverse:
+    """Verify diff/undiff roundtrip across large real-world texts."""
+
+    @pytest.mark.parametrize("file1", FILES)
+    @pytest.mark.parametrize("file2", FILES)
+    def test_roundtrip_files(self, file1: str, file2: str) -> None:
+        content1 = (RESOURCES_DIR / file1).read_text()[:50000]
+        content2 = (RESOURCES_DIR / file2).read_text()[:50000]
+
+        changes = diff(content1, content2)
+        actual = undiff(content1, changes)
+        assert actual == content2