1 files changed, 129 insertions, 0 deletions
diff --git a/tests/errors/formatting.test.py b/tests/errors/formatting.test.py
new file mode 100644
index 0000000..8cdf0ab
--- /dev/null
+++ b/tests/errors/formatting.test.py
@@ -0,0 +1,129 @@
+"""Tests for the message formatter helpers in :mod:`edify.errors.formatting`."""
+
+from unittest import mock
+
+from edify.errors.context import CallerContext
+from edify.errors.formatting import (
+    FixInsertion,
+    Problem,
+    compose_annotated_message,
+    format_error,
+    format_fix_block,
+    format_help_header,
+    format_note_line,
+    format_pointer_block,
+    format_problem,
+    format_problem_header,
+)
+
+
+def _context(source_line: str = "    x = do_the_thing(1, 2, 3)", colno: int = 9) -> CallerContext:
+    return CallerContext(
+        filename="/tmp/user_code.py",
+        lineno=42,
+        colno=colno,
+        end_colno=colno + 15,
+        source_line=source_line,
+    )
+
+
+def test_format_error_with_only_summary_returns_bare_header():
+    assert format_error("boom") == "error: boom"
+
+
+def test_format_error_with_summary_and_blocks_joins_them_with_blank_line():
+    output = format_error("boom", "first block", "second block")
+    assert output == "error: boom\n\nfirst block\n\nsecond block"
+
+
+def test_format_error_skips_empty_blocks():
+    output = format_error("boom", "", "only real block", "")
+    assert output == "error: boom\n\nonly real block"
+
+
+def test_format_pointer_block_draws_caret_at_caller_column():
+    context = _context()
+    block = format_pointer_block(context, "here")
+    lines = block.splitlines()
+    assert lines[0] == "  --> /tmp/user_code.py:42:9"
+    assert "^^^^^^^^^^^^^^^ here" in block
+
+
+def test_format_pointer_block_has_at_least_one_caret_when_span_is_empty():
+    context = CallerContext(
+        filename="/tmp/x.py",
+        lineno=1,
+        colno=5,
+        end_colno=5,
+        source_line="abcde",
+    )
+    block = format_pointer_block(context, "point")
+    assert "^ point" in block
+
+
+def test_format_note_line_prepends_the_note_prefix():
+    assert format_note_line("something is off") == "   = note: something is off"
+
+
+def test_format_problem_header_prepends_problem_prefix():
+    assert format_problem_header("stuff") == "problem: stuff"
+
+
+def test_format_help_header_prepends_help_prefix():
+    assert format_help_header("do X") == "help: do X"
+
+
+def test_format_fix_block_inserts_text_at_the_target_column():
+    context = _context(source_line="value = compute()", colno=1)
+    insertion = FixInsertion(column=9, text="new_")
+    block = format_fix_block(context, insertion)
+    assert "value = new_compute()" in block
+    assert "++++" in block
+
+
+def test_format_problem_composes_header_pointer_help_and_fix():
+    problem_context = _context(source_line="pattern = build()", colno=11)
+    fix_context = _context(source_line="pattern = build()", colno=11)
+    fix_insertion = FixInsertion(column=11, text=".digit()")
+    problem = Problem(
+        description="missing operand",
+        problem_context=problem_context,
+        problem_hint="no operand added",
+        help_summary="add .digit() before .build()",
+        fix_context=fix_context,
+        fix_insertion=fix_insertion,
+    )
+    output = format_problem(problem)
+    assert "problem: missing operand" in output
+    assert "no operand added" in output
+    assert "help: add .digit() before .build()" in output
+    assert "++++++++" in output
+
+
+def test_compose_annotated_message_when_caller_context_is_available():
+    output = compose_annotated_message(
+        summary="bad thing happened",
+        trigger_hint="right here",
+        note="because reasons",
+        help_line="help: do X",
+    )
+    assert output.startswith("error: bad thing happened")
+    assert "-->" in output
+    assert "= note: because reasons" in output
+    assert output.rstrip().endswith("help: do X")
+
+
+def test_compose_annotated_message_falls_back_when_caller_context_is_none():
+    with mock.patch(
+        "edify.errors.formatting.capture_caller_context", return_value=None
+    ):
+        output = compose_annotated_message(
+            summary="bad thing happened",
+            trigger_hint="here",
+            note="because reasons",
+            help_line="help: do X",
+        )
+    assert output.startswith("error: bad thing happened")
+    assert "-->" not in output
+    assert "= note: because reasons" in output
+    assert output.rstrip().endswith("help: do X")