[Tests] Remove deprecated and compatibility-only coverage

[yewentao256]

Purpose

Part of #39829

eg. drop pooling tests that only asserted deprecated warning paths

[gemini-code-assist]

Code Review

This pull request removes various deprecated tests and compatibility layers across the codebase, specifically targeting pooling tasks, weight utilities, argparse utilities, and KV connector integrations. However, feedback indicates that several tests—including those for deprecated KV scale mapping, argparse back-compatibility for the --model flag, and LMCache integration contracts—are being removed while the underlying implementation logic remains active in the repository, resulting in a significant loss of test coverage.

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tests/model_executor/test_weight_utils.py (105-110)

The test test_deprecated_kv_scale is being removed, but the corresponding compatibility logic in vllm/model_executor/model_loader/weight_utils.py (lines 1521-1538) is still present in the codebase. Removing tests for features that are still active and supported (even if deprecated) increases the risk of regressions. It is recommended to retain these tests until the underlying code is actually removed from the repository.

tests/utils_/test_argparse_utils.py (279-321)

This PR removes the test coverage for the --model argument back-compatibility in vllm serve. However, the remapping logic and the associated warning are still present in vllm/utils/argparse_utils.py (lines 185-217). Furthermore, the commented-out test block intended for when compatibility ends is also being deleted. It is safer to keep these tests active as long as the code they verify remains in the repository, or to update the code to the final state (raising an error) and update the tests accordingly to ensure the transition is correctly enforced.

tests/v1/kv_connector/unit/test_lmcache_integration.py (1-229)

Removing test_lmcache_integration.py eliminates critical contract tests that ensure vLLM's internal changes do not break the LMCache integration. These tests verify that key attributes and methods on classes like VllmConfig, ModelConfig, and Request remain stable. Unless the LMCache integration is also being removed or these tests have been moved to a different suite, this represents a significant loss in integration testing coverage for a major external component.

[noooop]

For pooling-related tests, please wait for #37861 to land in v0.20.0.

These tests are important before this, please do not remove them.