Add gemma4 unit tests

[apsonawane]

This pull request adds a comprehensive test suite for the Gemma4 multimodal model, covering model loading, text-only and vision (image) processing, and validation of ONNX model input/output interfaces. These tests ensure that the Gemma4 model and its components function as expected for both text and image modalities.

The most important changes include:

New test coverage for Gemma4 multimodal model:

• Added unit tests for loading the Gemma4 model and verifying basic text-only and image processing functionality using the onnxruntime_genai library (test_gemma4_models.py).
• Added parameterized tests for image input, including loading images from file paths and bytes, as well as handling multiple images in a single prompt.
• Verified that the multimodal processor correctly generates required input fields such as input_ids, pixel_values, and token_type_ids.

ONNX model interface validation:

• Added tests to validate the required inputs and outputs for the vision, embedding, and text/decoder ONNX models, ensuring compatibility and correct wiring of model components.
• Included checks for input/output names, data types, and dynamic shapes, particularly for the vision model’s pixel_values input.

[Copilot]

Pull request overview

Adds a new Python pytest module intended to validate Gemma4 multimodal integration in onnxruntime_genai, including basic processor behavior (text-only and vision) and ONNX I/O interface checks for the vision/embedding/decoder components.

Changes:

• Introduces test/python/test_gemma4_models.py with Gemma4 model load + multimodal processor tests.
• Adds image-path, image-bytes, and multi-image prompt preprocessing coverage for Gemma4.
• Adds ONNX graph interface validation assertions for Gemma4 dummy vision/embedding/text models.

[baijumeswani]

Do these tests only run locally or was the intention to also enable it in the CI pipeline?

[Copilot]

Pull request overview

Copilot reviewed 6 out of 10 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 13 changed files in this pull request and generated 3 comments.