Pretty-print JSON test snapshots + tighten test module quality

**Pretty-print snapshots**

The `test_show_options*.json` snapshots used by `tests/test_*.py` were
single-line JSON arrays — typically 1-2 KB strings with ~100 country or
currency names crammed onto one line. When a database update adds or
removes a single country, the diff in CI/PR reviews is one giant string
change with no way to see what actually differs.

Switched `json.dumps()` in `tests/conftest.py` to use `indent=2` and
`ensure_ascii=False` so each array element lands on its own line and
non-ASCII characters render natively (e.g. "Côte d'Ivoire" instead of
escaped sequences). Diffs in future data PRs now show exactly which
country/currency/exchange was added or removed.

Regenerated all 54 snapshot files via `pytest --rewrite-expected`. No
test semantics change — content is identical.

**Test module quality fixes (free with the regen)**

Since the regen touched every test file, took the opportunity to:

 * Fix wrong module docstrings (`test_equities.py` and
   `test_moneymarkets.py` both started with "Currencies Test Module")
 * Replace `# pylint: disable=missing-function-docstring` with actual
   one-line docstrings on each test function
 * Add type hints: `(recorder: Recorder) -> None` on test signatures,
   guarded behind `from __future__ import annotations` so the import
   stays under `TYPE_CHECKING` and adds no runtime cost

No test was renamed or parametrized — that would have invalidated the
positional snapshot naming (`test_select.csv`, `test_select_1.csv`, …)
that `Recorder.capture()` relies on. Refactors that change snapshot
naming were intentionally kept out of scope.

All 31 tests pass.

Author: dokson

tests/conftest.py

@@ -1,3 +1,4 @@
+import difflib
 import json
 import os
 import pathlib
@@ -43,7 +44,7 @@ def extract_string(data: Any, **kwargs) -> str:
                 **kwargs,
             )
         elif isinstance(data, tuple(EXTENSIONS_MATCHING["json"])):
-            string_value = json.dumps(data, **kwargs)
+            string_value = json.dumps(data, indent=2, ensure_ascii=False, **kwargs)
         else:
             raise AttributeError(f"Unsupported type : {type(data)}")
 
@@ -225,19 +226,39 @@ def assert_equal(self):
 
         for record in record_list:
             if record.record_changed:
+                expected = (record.recorded or "").splitlines()
+                actual = (record.captured or "").splitlines()
+                diff = "\n".join(
+                    difflib.unified_diff(
+                        expected,
+                        actual,
+                        fromfile="expected",
+                        tofile="actual",
+                        lineterm="",
+                        n=3,
+                    )
+                )
+                if not diff:
+                    diff = (
+                        f"(line-level diff empty — content differs only in trailing whitespace or EOL)\n"
+                        f"expected length={len(record.recorded or '')}, "
+                        f"actual length={len(record.captured or '')}"
+                    )
                 raise AssertionError(
-                    "Change detected\n"
-                    f"Record    : {record.record_path}\n"
-                    f"Expected  : {record.recorded[:self.display_limit]}\n"
-                    f"Actual    : {record.captured[:self.display_limit]}\n"
+                    f"Snapshot mismatch: {record.record_path}\n"
+                    f"Run pytest with --rewrite-expected to regenerate, or inspect the diff below.\n\n"
+                    f"{diff}"
                 )
 
     def assert_in_list(self, in_list: list[str]):
         record_list = self.__record_list
 
         for record in record_list:
             for string_value in in_list:
-                assert string_value in record.captured  # noqa
+                assert string_value in record.captured, (  # noqa: S101
+                    f"Expected substring {string_value!r} not found in "
+                    f"{record.record_path}"
+                )
 
     def persist(self):
         record_list = self.__record_list

tests/json/test_cryptos/test_show_options.json

@@ -1 +1,4 @@
-["cryptocurrency", "currency"]
+[
+  "cryptocurrency",
+  "currency"
+]