test: cover char-span line-range helper

surfsense_backend/tests/unit/utils/test_text_spans.py

@@ -0,0 +1,39 @@
+"""Unit tests for char-span -> line-range conversion."""
+
+from __future__ import annotations
+
+import pytest
+
+from app.utils.text_spans import char_span_to_line_range
+
+pytestmark = pytest.mark.unit
+
+_TEXT = "line1\nline2\nline3"
+
+
+def test_single_line_span() -> None:
+    start = _TEXT.index("line2")
+    assert char_span_to_line_range(_TEXT, start, start + len("line2")) == (2, 2)
+
+
+def test_first_line_span() -> None:
+    assert char_span_to_line_range(_TEXT, 0, len("line1")) == (1, 1)
+
+
+def test_last_line_span() -> None:
+    start = _TEXT.index("line3")
+    assert char_span_to_line_range(_TEXT, start, len(_TEXT)) == (3, 3)
+
+
+def test_multi_line_span() -> None:
+    # "line1\nline2" spans lines 1-2.
+    assert char_span_to_line_range(_TEXT, 0, _TEXT.index("line2") + 5) == (1, 2)
+
+
+def test_empty_span_resolves_to_its_line() -> None:
+    start = _TEXT.index("line2")
+    assert char_span_to_line_range(_TEXT, start, start) == (2, 2)
+
+
+def test_offsets_clamped_to_text_bounds() -> None:
+    assert char_span_to_line_range(_TEXT, -5, 10_000) == (1, 3)