[bentsku]

Motivation

SnapshotMatchResult compares recorded and observed state with DeepDiff, which defaults to ignore_private_variables=True. That setting also skips dict keys starting with __, so any value under such a key was never verified, and snapshot tests passed whatever the response contained there:

DeepDiff({"__schema": 1}, {"__schema": 2})                                  # {} -> "match"
DeepDiff({"__schema": 1}, {"__schema": 2}, ignore_private_variables=False)  # diff

Affected keys include __type (the error type in AWS JSON-protocol error responses) and GraphQL __typename / __schema. This came up in AppSync, where an introspection response under data.__schema differed from the AWS recording but the test still passed.

Tracked in AWS-2688.

Changes

• Pass ignore_private_variables=False to DeepDiff in SnapshotMatchResult.
• Add tests: __ key mismatches fail (top-level, nested, inside list items), equal __ keys pass, and skip_verification_paths such as $..__type still skip them. The four mismatch tests fail without the fix.

match_object is unaffected: it drops keys starting with _ itself before diffing.

Impact on consumers

Snapshot tests whose __ keys differ from the recording will now fail. Each one is a parity difference that was previously hidden. Fix the provider, add a transformer, or skip the path, e.g. @markers.snapshot.skip_snapshot_verify(paths=["$..__type"]).

🤖 Generated with Claude Code