feat: Add unit tests for line_utils functions

backend/tests/test_line_utils.py

@@ -0,0 +1,259 @@
+"""Tests for line number tracking utilities in line_utils."""
+
+import pytest
+
+from app.services.line_utils import (
+    find_function_lines,
+    find_lines_matching_pattern,
+    find_undocumented_lines,
+    format_code_snippet,
+    get_line_content,
+    get_lines_range,
+    group_consecutive_lines,
+    is_code_line,
+)
+
+
+# ── get_line_content ──────────────────────────────────────────────────────────
+
+@pytest.mark.parametrize(
+    ("code", "line_number", "expected"),
+    [
+        ("", 1, ""),
+        ("", 0, ""),
+        ("", -1, ""),
+        ("single", 1, "single"),
+        ("single", 2, ""),
+        ("single", 0, ""),
+        ("single", -1, ""),
+        ("line one\nline two\nline three", 1, "line one"),
+        ("line one\nline two\nline three", 2, "line two"),
+        ("line one\nline two\nline three", 3, "line three"),
+        ("line one\nline two\nline three", 4, ""),
+        ("line one\nline two\nline three", 0, ""),
+        ("line one\nline two\nline three", -1, ""),
+        ("a\nb\nc\nd\ne", 5, "e"),
+        ("a\nb\nc\nd\ne", 6, ""),
+    ],
+)
+def test_get_line_content(code, line_number, expected):
+    assert get_line_content(code, line_number) == expected
+
+
+# ── get_lines_range ───────────────────────────────────────────────────────────
+
+@pytest.mark.parametrize(
+    ("code", "start", "end", "expected"),
+    [
+        ("", 1, 1, []),
+        ("a\nb\nc", 1, 3, ["a", "b", "c"]),
+        ("a\nb\nc", 0, 2, ["a", "b"]),
+        ("a\nb\nc", -1, 2, ["a", "b"]),
+        ("a\nb\nc", 1, 0, []),
+        ("a\nb\nc", 2, 2, ["b"]),
+        ("a\nb\nc", 3, 3, ["c"]),
+        ("a\nb\nc", 4, 5, []),
+        ("a\nb\nc", -5, -1, ["a", "b"]),
+        ("a\nb\nc", 0, 10, ["a", "b", "c"]),
+        ("x\ny\nz\nw\nv", 2, 4, ["y", "z", "w"]),
+        ("x\ny\nz\nw\nv", 3, 2, []),
+    ],
+)
+def test_get_lines_range(code, start, end, expected):
+    assert get_lines_range(code, start, end) == expected
+
+
+# ── format_code_snippet ───────────────────────────────────────────────────────
+
+def test_format_code_snippet_marker_placement():
+    code = "def foo():\n    pass\nbar = 1\n"
+    result = format_code_snippet(code, [2])
+    assert ">>> 2:     pass" in result
+
+
+def test_format_code_snippet_context_line_clamping_at_start():
+    code = "a\nb\nc\nd\ne\n"
+    result = format_code_snippet(code, [1], context_lines=3)
+    # Should not go beyond line 1 on the start side
+    lines = result.splitlines()
+    assert lines[0].startswith(">>> 1:")
+
+
+def test_format_code_snippet_context_line_clamping_at_end():
+    code = "a\nb\nc\nd\ne\n"
+    result = format_code_snippet(code, [5], context_lines=3)
+    lines = result.splitlines()
+    # Line 5 is at the end boundary; context should not go beyond it
+    assert lines[-1].startswith(">>> 5:")
+
+
+def test_format_code_snippet_large_codebase_stable_output():
+    code = "\n".join(f"line_{i}" for i in range(1000)) + "\n"
+    result = format_code_snippet(code, [500, 501, 502], context_lines=2)
+    assert ">>> 500: line_499" in result
+    assert ">>> 501: line_500" in result
+    assert ">>> 502: line_501" in result
+
+
+def test_format_code_snippet_empty_line_numbers():
+    code = "a\nb\nc\n"
+    result = format_code_snippet(code, [])
+    assert ">>>" not in result
+
+
+def test_format_code_snippet_escapes_script_tags():
+    code = "<script>alert(1)</script>\n"
+    result = format_code_snippet(code, [1])
+    assert "&lt;script" in result
+    assert "&lt;/script&gt;" in result
+
+
+# ── find_lines_matching_pattern ───────────────────────────────────────────────
+
+def test_find_lines_matching_pattern_empty_input():
+    assert find_lines_matching_pattern("", r"\d+") == []
+
+
+def test_find_lines_matching_pattern_malformed_regex_raises():
+    # Malformed regex raises PatternError instead of returning silently
+    with pytest.raises(Exception):  # noqa: BLE001 - testing error behavior
+        find_lines_matching_pattern("hello", r"[invalid")
+
+
+def test_find_lines_matching_pattern_large_document():
+    code = "\n".join(f"line {i}" for i in range(500)) + "\n"
+    result = find_lines_matching_pattern(code, r"line \d+")
+    assert len(result) == 500
+
+
+def test_find_lines_matching_pattern_case_insensitive():
+    code = "Hello\nHELLO\nhello\nHeLLo\n"
+    result = find_lines_matching_pattern(code, r"hello")
+    assert result == [1, 2, 3, 4]
+
+
+def test_find_lines_matching_pattern_no_match():
+    code = "alpha\nbeta\ngamma\n"
+    result = find_lines_matching_pattern(code, r"zeta")
+    assert result == []
+
+
+# ── group_consecutive_lines ───────────────────────────────────────────────────
+
+def test_group_consecutive_lines_empty_list():
+    assert group_consecutive_lines([]) == []
+
+
+def test_group_consecutive_lines_single_element():
+    assert group_consecutive_lines([5]) == [(5, 5)]
+
+
+def test_group_consecutive_lines_consecutive():
+    assert group_consecutive_lines([1, 2, 3, 4, 5]) == [(1, 5)]
+
+
+def test_group_consecutive_lines_non_consecutive():
+    result = group_consecutive_lines([1, 2, 4, 5, 7])
+    assert result == [(1, 2), (4, 5), (7, 7)]
+
+
+def test_group_consecutive_lines_with_duplicates():
+    result = group_consecutive_lines([3, 1, 2, 3, 1])
+    assert result == [(1, 3)]
+
+
+def test_group_consecutive_lines_unsorted():
+    result = group_consecutive_lines([10, 8, 9, 7, 6])
+    assert result == [(6, 10)]
+
+
+# ── find_function_lines ───────────────────────────────────────────────────────
+
+def test_find_function_lines_empty_code():
+    assert find_function_lines("", "Python") == []
+
+
+def test_find_function_lines_python_single():
+    code = 'def foo():\n    pass\n'
+    result = find_function_lines(code, "Python")
+    assert len(result) == 1
+    assert result[0]["name"] == "foo"
+    assert result[0]["start_line"] == 1
+
+
+def test_find_function_lines_python_multiple():
+    code = 'def foo():\n    pass\n\ndef bar():\n    pass\n'
+    result = find_function_lines(code, "Python")
+    assert len(result) == 2
+    assert result[0]["name"] == "foo"
+    assert result[1]["name"] == "bar"
+
+
+def test_find_function_lines_javascript():
+    code = 'function foo() {}\n'
+    result = find_function_lines(code, "JavaScript")
+    assert len(result) == 1
+    assert result[0]["name"] == "foo"
+
+
+def test_find_function_lines_unsupported_language():
+    assert find_function_lines("x", "Ruby") == []
+
+
+# ── find_undocumented_lines ───────────────────────────────────────────────────
+
+def test_find_undocumented_lines_empty_code():
+    assert find_undocumented_lines("") == []
+
+
+def test_find_undocumented_lines_all_commented():
+    code = "# comment\n// another\n"
+    assert find_undocumented_lines(code) == []
+
+
+def test_find_undocumented_lines_mixed():
+    code = "# docstring\nx = 1\ny = 2\n"
+    result = find_undocumented_lines(code)
+    # Both code lines have a nearby comment, so none are undocumented
+    assert result == []
+
+
+def test_find_undocumented_lines_with_nearby_comment():
+    code = "x = 1\n# comment\ny = 2\n"
+    result = find_undocumented_lines(code)
+    # x=1 has no preceding comment; y=2 has the # comment within range
+    assert result == [1]
+
+
+# ── is_code_line ──────────────────────────────────────────────────────────────
+
+def test_is_code_line_empty():
+    assert not is_code_line("")
+
+
+def test_is_code_line_whitespace_only():
+    assert not is_code_line("   \n  ")
+
+
+def test_is_code_line_comment_hash():
+    assert is_code_line("# comment") is False
+
+
+def test_is_code_line_comment_slash():
+    assert is_code_line("// comment") is False
+
+
+def test_is_code_line_docstring_triple_double():
+    assert is_code_line('"""docstring"""') is False
+
+
+def test_is_code_line_docstring_triple_single():
+    assert is_code_line("'''docstring'''") is False
+
+
+def test_is_code_line_actual_code():
+    assert is_code_line("x = 1") is True
+
+
+def test_is_code_line_with_leading_whitespace():
+    assert is_code_line("    x = 1") is True