[adamreeve]

Rationale for this change

More test coverage.

What changes are included in this PR?

• Updates the parquet-testing submodule.
• Adds a new test case for the test file added in Add encrypted Parquet file using AES-CTR and a plaintext footer parquet-testing#130
• Allows regenerating the test files by setting a PARQUET_ENCRYPTION_TEST_OUTPUT_DIR environment variable when running the tests. This could be useful if we need to generate similar test files in the future.

Are these changes tested?

Yes

Are there any user-facing changes?

No

Was AI used for this PR?

In accordance to the AI generation guidelines, please disclose below whether and how AI was used in this PR.

PR code and description written by:

• Human
• AI (code only, not description)

Reviewed before submission by:

• Human
• AI
• Not reviewed

• GitHub Issue: [C++][Parquet] Add new test case for AES-CTR with plaintext footer file in parquet-testing #55406

[Copilot]

🟢 Approval recommended

No active review issues are reported for the added Parquet encryption test coverage and fixture-generation support.

No open issues 🎉

What changed in this PR

Expands Parquet encryption test coverage for AES-CTR files with plaintext footers, addressing GH-55406, and adds support for regenerating encrypted test fixtures.

Changes:

• Adds write and read coverage for the plaintext-footer AES-CTR configuration, including reads without decryption keys.
• Adds optional fixture export through PARQUET_ENCRYPTION_TEST_OUTPUT_DIR, using settings that match parquet-testing files.

File	Description
cpp/​src/​parquet/​encryption/​write_configurations_test.cc	Adds the encryption configuration and optional fixture export with a Snappy requirement.
cpp/​src/​parquet/​encryption/​test_encryption_util.h	Declares fixture-generation settings and the factory method.
cpp/​src/​parquet/​encryption/​test_encryption_util.cc	Implements the fixture layout and applies compression, version, and encoding settings.
cpp/​src/​parquet/​encryption/​read_configurations_test.cc	Adds the AES-CTR plaintext-footer fixture to decryption and legacy-read coverage.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

No active review issues block the AES-CTR plaintext-footer coverage and fixture-export changes.

No open issues 🎉

_{Review effort: Balanced}