chore(trainer): add unit tests for get_args_using_torchtune_config and get_trainer_cr_from_builtin_trainer

[prabhaharanv]

What this PR does

Adds comprehensive unit tests for two previously untested utility functions in kubeflow/trainer/backends/kubernetes/utils.py:

test_get_args_using_torchtune_config — 8 parametrized test cases:

1. Empty TorchTuneConfig produces empty args
2. dtype only produces single dtype arg
3. All scalar fields (dtype, batch_size, epochs, loss)
4. peft_config with LoraConfig appends LoRA args
5. dataset_preprocess_config appends dataset args
6. HuggingFace dataset URI — directory path via initializer (hf://tatsu-lab/alpaca)
7. HuggingFace dataset URI — file path via initializer (hf://tatsu-lab/alpaca/data.json)
8. Invalid dtype raises ValueError

test_get_trainer_cr_from_builtin_trainer — 4 parametrized test cases:

1. Config with num_nodes and batch_size
2. Config with resources_per_node
3. Empty config produces trainer with empty args
4. Invalid config type raises ValueError

Why

Both get_args_using_torchtune_config() and get_trainer_cr_from_builtin_trainer() had zero test coverage — confirmed via grep across the entire test suite. These functions are critical for converting SDK BuiltinTrainer types into Kubernetes CR models and CLI arguments for torchtune.

How

• Tests follow existing patterns in utils_test.py using TestCase dataclass and pytest.mark.parametrize
• Added helper _build_builtin_runtime() to construct a torchtune runtime with TORCH_TUNE_COMMAND
• All 93 tests pass (81 existing + 12 new), zero regressions
• Passes ruff check, ruff format --check, and pre-commit hooks

[github-actions]

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[google-oss-prow]

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[Copilot]

Pull request overview

Adds unit tests to improve coverage for TorchTune/BuiltinTrainer Kubernetes utility conversions, ensuring TorchTuneConfig fields and BuiltinTrainer CR generation behave as expected.

Changes:

• Added _build_builtin_runtime() helper for constructing a TorchTune BuiltinTrainer runtime in tests.
• Added parametrized tests for utils.get_args_using_torchtune_config().
• Added parametrized tests for utils.get_trainer_cr_from_builtin_trainer().

[Copilot]

The PR description lists several test scenarios (e.g., “model_args only” and a “full config with all fields”) that aren’t represented in this parametrization, and TorchTuneConfig doesn’t appear to have a model_args field; please add the missing cases or update the PR description to match what’s actually tested.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.