diff --git a/tests/test_canonical_corpus_additional.py b/tests/test_canonical_corpus_additional.py
new file mode 100644
index 0000000..d914e00
--- /dev/null
+++ b/tests/test_canonical_corpus_additional.py
@@ -0,0 +1,51 @@
+"""Focused tests for ``iav.canonical_corpus`` helpers."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+import pytest
+
+from iav.canonical_corpus import (
+    _assert_close,
+    _corpus_path,
+    bundled_corpus_resource,
+    export_corpus_json,
+)
+
+
+def test_assert_close_within_tolerance_passes():
+    _assert_close(1.0, 1.0005, 0.01, "pair_score", "dyad_perfect_fifth")
+
+
+def test_assert_close_outside_tolerance_raises():
+    with pytest.raises(AssertionError) as excinfo:
+        _assert_close(0.5, 0.9, 0.01, "pair_score", "dyad_perfect_fifth")
+
+    message = str(excinfo.value)
+    assert "dyad_perfect_fifth.pair_score" in message
+    assert "got 0.500000" in message
+    assert "expected 0.900000" in message
+    assert "tol=0.01" in message
+
+
+def test_bundled_corpus_resource_returns_package_resource_id():
+    assert bundled_corpus_resource() == "iav.data:canonical_sonorities.json"
+
+
+def test_export_corpus_json_writes_bundled_corpus(tmp_path: Path):
+    output_path = tmp_path / "exported_canonical_sonorities.json"
+
+    export_corpus_json(output_path)
+
+    assert output_path.is_file()
+    text = output_path.read_text(encoding="utf-8")
+    assert text.strip()
+
+    exported = json.loads(text)
+    bundled = json.loads(_corpus_path().read_text(encoding="utf-8"))
+
+    assert set(exported) >= {"schema_version", "edo", "bin_cents", "sonorities"}
+    assert exported["schema_version"] == bundled["schema_version"]
+    assert exported["sonorities"].keys() == bundled["sonorities"].keys()