tests(spanner): avoid table name collisions in tests (#18001)

# Fix Spanner Test Flakes: Avoid Generic Table Names

## Problem
The `sqlalchemy-spanner` test suite occasionally fails with `Duplicate
name in schema: t.` errors. This happens because multiple tests use the
generic table name `t`. In a shared database environment, or due to
buffered DDL statements in Spanner (which are non-transactional), a
table from a previous test might still exist when a new test tries to
create it.

## Solution
Renamed the generic table name `t` to more specific names in several
tests and fixtures to avoid collisions.

- In `tests/conftest.py`, renamed `t` to `t_literal_round_trip_spanner`.
- In `tests/test_suite_14.py`:
- Renamed `t` to `t_nullable_reflection` in `test_nullable_reflection`.
  - Renamed `t` to `t_type_round_trip` in `_type_round_trip`.
  - Renamed `t` to `t_percent_signs` in `EscapingTest`.
  - Renamed `t` to `t_do_numeric` in `NumericTest`.

## Notes to Reviewers
These changes are purely in test code and aim to improve test stability
by eliminating shared resource name collisions.

Author: chalmerlowe

packages/sqlalchemy-spanner/tests/conftest.py

@@ -71,7 +71,7 @@ def run(
         compare=None,
         support_whereclause=True,
     ):
-        t = Table("t", metadata, Column("x", type_))
+        t = Table("t_literal_round_trip_spanner", metadata, Column("x", type_))
         t.create(connection)
 
         for value in input_:

packages/sqlalchemy-spanner/tests/test_suite_14.py

@@ -25,7 +25,9 @@
 import pytest
 import sqlalchemy
 from google.api_core.datetime_helpers import DatetimeWithNanoseconds
+from google.cloud import spanner_dbapi
 from google.cloud.spanner_v1 import Client, RequestOptions
+from google.cloud.sqlalchemy_spanner import version as sqlalchemy_spanner_version
 from sqlalchemy import (
     FLOAT,
     Boolean,
@@ -204,8 +206,6 @@
 )
 from sqlalchemy.types import Integer, Numeric, Text
 
-from google.cloud import spanner_dbapi
-from google.cloud.sqlalchemy_spanner import version as sqlalchemy_spanner_version
 from tests._helpers import get_db_url, get_project
 
 config.test_schema = ""
@@ -250,7 +250,7 @@ class ComponentReflectionTestExtra(_ComponentReflectionTestExtra):
     @testing.requires.table_reflection
     def test_nullable_reflection(self, connection, metadata):
         t = Table(
-            "t",
+            "t_nullable_reflection",
             metadata,
             Column("a", Integer, nullable=True),
             Column("b", Integer, nullable=False),
@@ -260,19 +260,21 @@ def test_nullable_reflection(self, connection, metadata):
         eq_(
             dict(
                 (col["name"], col["nullable"])
-                for col in inspect(connection).get_columns("t")
+                for col in inspect(connection).get_columns("t_nullable_reflection")
             ),
             {"a": True, "b": False},
         )
 
     def _type_round_trip(self, connection, metadata, *types):
         t = Table(
-            "t", metadata, *[Column("t%d" % i, type_) for i, type_ in enumerate(types)]
+            "t_type_round_trip",
+            metadata,
+            *[Column("t%d" % i, type_) for i, type_ in enumerate(types)],
         )
         t.create(connection)
         connection.connection.commit()
 
-        return [c["type"] for c in inspect(connection).get_columns("t")]
+        return [c["type"] for c in inspect(connection).get_columns("t_type_round_trip")]
 
     @testing.requires.table_reflection
     def test_numeric_reflection(self, connection, metadata):
@@ -1207,7 +1209,7 @@ def test_percent_sign_round_trip(self):
         Overriding the test to avoid the same failure.
         """
         m = self.metadata
-        t = Table("t", m, Column("data", String(50)))
+        t = Table("t_percent_signs", m, Column("data", String(50)))
         t.create(config.db)
         with config.db.begin() as conn:
             conn.execute(t.insert(), dict(data="some % value"))
@@ -1551,7 +1553,7 @@ def do_numeric_test(self, metadata, connection):
         @testing.emits_warning(r".*does \*not\* support Decimal objects natively")
         def run(type_, input_, output, filter_=None, check_scale=False):
             t = Table(
-                "t",
+                "t_do_numeric",
                 metadata,
                 Column("x", type_),
                 Column("id", Integer, primary_key=True),