File the SessionConfig tests with the other SessionConfig tests

The two `SessionConfig.set` tests went into `test_plans.py` because they were
committed alongside the `execute` bounds check, not because they have anything
to do with plans. `test_context.py` is where `SessionConfig` construction is
already covered, and it now also holds the three constructor tests for the
other half of the same panic defect.

Move them there, ahead of the constructor cases so the method they refer back
to is read first, and fold the duplicated note about `PanicException` deriving
from `BaseException` into the first of the five. `test_plans.py` keeps its
`SessionConfig` import for the `with_target_partitions` calls in the
partitioning tests. No assertion changed.

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

Author: timsaucer

python/tests/test_context.py

@@ -103,6 +103,26 @@ def test_create_context_with_all_valid_args():
         ctx.catalog("datafusion")
 
 
+def test_session_config_set_rejects_an_unknown_namespace():
+    """A bad config key raises rather than aborting through a Rust panic.
+
+    `datafusion.runtime.*` appears in `information_schema.df_settings` but has
+    no `ConfigOptions` namespace, so it is the key a naive "read the settings
+    back and replay them on the worker" loop hits first.
+    """
+    # `ValueError`, not a bare `Exception`: a panic would arrive as
+    # `PanicException`, which derives from `BaseException` and so would not be
+    # caught here at all. Both this and the constructor cases below rely on it.
+    with pytest.raises(ValueError, match="runtime"):
+        SessionConfig().set("datafusion.runtime.memory_limit", "unlimited")
+
+
+def test_session_config_set_rejects_an_unparsable_value():
+    """A well-known key with a value of the wrong type raises too."""
+    with pytest.raises(ValueError, match="batch_size"):
+        SessionConfig().set("datafusion.execution.batch_size", "not_an_int")
+
+
 def test_session_config_constructor_applies_options():
     """A dict passed to the constructor reaches the session's options."""
     config = SessionConfig(
@@ -130,9 +150,6 @@ def test_session_config_constructor_rejects_an_unknown_namespace():
 
     The same defect as `SessionConfig.set` had, reached through the argument
     that a replayed `information_schema.df_settings` dictionary arrives in.
-    `ValueError`, not a bare `Exception`: a panic would arrive as
-    `PanicException`, which derives from `BaseException` and so would not be
-    caught here at all.
     """
     with pytest.raises(ValueError, match="runtime"):
         SessionConfig({"datafusion.runtime.memory_limit": "unlimited"})

python/tests/test_plans.py

@@ -269,26 +269,6 @@ def test_physical_partitioning_equality_is_structural() -> None:
     assert len({scan, other_scan, grouped}) == 2
 
 
-def test_session_config_set_rejects_an_unknown_namespace() -> None:
-    """A bad config key raises rather than aborting through a Rust panic.
-
-    `datafusion.runtime.*` appears in `information_schema.df_settings` but has
-    no `ConfigOptions` namespace, so it is the key a naive "read the settings
-    back and replay them on the worker" loop hits first.
-    """
-    # `ValueError`, not a bare `Exception`: a panic would arrive as
-    # `PanicException`, which derives from `BaseException` and so would not be
-    # caught here at all.
-    with pytest.raises(ValueError, match="runtime"):
-        SessionConfig().set("datafusion.runtime.memory_limit", "unlimited")
-
-
-def test_session_config_set_rejects_an_unparsable_value() -> None:
-    """A well-known key with a value of the wrong type raises too."""
-    with pytest.raises(ValueError, match="batch_size"):
-        SessionConfig().set("datafusion.execution.batch_size", "not_an_int")
-
-
 def test_installing_a_physical_codec_preserves_strict_mode() -> None:
     """Installing a physical extension codec must not re-enable inlining.