test(thoughtspot): pin the last three loops that an empty collection satisfied

The remainder of the fail-open sweep. These were lower priority than the six in
cc5db0e because a sibling test happened to fail on the same mutation -- but
"another test noticed" is not the same as this test working, and the sibling can
be deleted or narrowed later without anyone seeing the cover disappear.

`test_every_table_or_sql_view_document_is_present` compares two sets, and
`set() == set()` holds, so a fixture with no table documents satisfied it and
the two sibling tests that walk the same collection. Pinned once for all three.

`test_column_type_is_never_a_bare_root_key` reads columns through a helper that
ends `or []`, so a model emitting no columns passed without checking one.

Not changed, deliberately: the ~16 tests whose loop iterable is a literal list
written inline in the test body. Those can only go empty if someone edits the
assertion out by hand, which no guard can prevent, and the six catalog
`test_classifications` tests already have a sibling pinning an exact row count.

942 tests pass.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: djwaldo

converters/thoughtspot/tests/test_ossie_to_thoughtspot_model.py

@@ -510,6 +510,9 @@ def test_column_type_is_never_a_bare_root_key(self):
         doc = build_model(model, [orders], IssueLog())
         columns, _formulas = _all_columns_and_formulas(doc.body)
 
+        # `_all_columns_and_formulas` reads `body.get("columns") or []`, so an
+        # emitted model with no columns would pass this without checking one.
+        assert columns, "build_model emitted no columns to check placement on"
         for column in columns:
             assert "column_type" not in column
             assert column["properties"]["column_type"] in ("ATTRIBUTE", "MEASURE")

converters/thoughtspot/tests/test_roundtrip.py

@@ -198,17 +198,23 @@ def test_every_table_or_sql_view_document_is_present(self, fixture_name):
         document_set, _, tml_result = _tml_roundtrip(fixture_name)
         original_names = {t.body["name"] for t in document_set.tables}
         new_names = {t.body["name"] for t in tml_result.documents.tables}
+        # `set() == set()` is true, so the fixture having no tables at all would
+        # satisfy this and the two sibling tests below, which walk the same
+        # collection. Pinned here once, for all three.
+        assert original_names, f"{fixture_name} has no table documents to compare"
         assert new_names == original_names
 
     def test_every_physical_column_survives_with_its_exact_content(self, fixture_name):
         document_set, _, tml_result = _tml_roundtrip(fixture_name)
+        assert document_set.tables, f"{fixture_name} has no table documents"
         for original in document_set.tables:
             new = _table_by_name(tml_result.documents, original.body["name"])
             assert new.kind == original.kind
             assert _columns_by_name(new.body) == _columns_by_name(original.body)
 
     def test_shared_table_level_attributes_survive(self, fixture_name):
         document_set, _, tml_result = _tml_roundtrip(fixture_name)
+        assert document_set.tables, f"{fixture_name} has no table documents"
         for original in document_set.tables:
             new = _table_by_name(tml_result.documents, original.body["name"])
             # "joins_with" included: a Table-referenced join's own