test(vllm): drop tests of APIs removed by PR #22 refactor

[aoshen02]

Summary

Follow-up to @knlnguyen1802's request on #22 (comment) to send a small PR against update_weights_tensor rather than a manual edit.

Same kind of test/production drift as the one cleaned up in commit 2ee402b "Fix test", but for the other 8 unit tests that were also broken by the 132066f "Fix colocated mode weight sync" refactor.

On the current update_weights_tensor HEAD, pytest tests/unit/backends/vllm_utils/test_vllm_engine.py returns 8 failed, 18 passed. After this PR: 20 passed.

What broke

PR #22 commit 132066f removed / inlined three things in slime/backends/vllm_utils/vllm_engine.py:

Removed API	Replacement
VLLMEngine._weight_transfer_http_timeout()	Inlined float(os.environ.get("SLIME_VLLM_WEIGHT_TRANSFER_HTTP_TIMEOUT_SEC", "900")) in start_weight_update / finish_weight_update; _post_vllm_update_weights_http uses a slightly different env-var precedence
Module-level _response_json_or_fallback(response)	Inlined try: return response.json() except Exception: return {"ok": True, "raw": response.text}
_http_base() init-guard (RuntimeError when server_host unset)	Removed; now bare attribute access

But PR #21 had added tests against those exact APIs in tests/unit/backends/vllm_utils/test_vllm_engine.py, and commit 2ee402b only cleaned up the two _skipped_if_not_leader tests, leaving the other 8 drifting.

What this PR does

Deletes 6 tests of fully-removed APIs:

• test_weight_transfer_http_timeout_reads_env
• test_weight_transfer_http_timeout_fallback_to_legacy_env
• test_response_json_or_fallback_parses_dict
• test_response_json_or_fallback_non_dict_wrapped
• test_response_json_or_fallback_invalid_json
• test_http_base_requires_init (the happy path is still covered by test_http_base_ipv6_host)

Trims the dead _weight_transfer_http_timeout() reference from 2 tests but keeps their endpoint/payload assertions, which still pin real production behavior:

• test_start_weight_update_posts_four_phase_endpoint
• test_finish_weight_update_posts_empty_body

Verification

$ pytest tests/unit/backends/vllm_utils/test_vllm_engine.py -q
....................                                                     [100%]
20 passed in 2.24s

$ pytest tests/unit/ --ignore=tests/unit/backends/megatron_utils -q
53 passed, 2 warnings in 29.38s

$ pre-commit run --all-files
... all hooks Passed

Diff is +3/-52 in a single file.

[gemini-code-assist]

Code Review

This pull request removes several unit tests and assertions related to weight transfer HTTP timeouts and JSON response fallback handling in test_vllm_engine.py. The reviewer suggests that instead of completely removing the timeout assertions, the tests should verify that the default timeout of 900.0 seconds is correctly passed.

[gemini-code-assist]

Instead of completely removing the timeout assertion, we should verify that the default timeout of 900.0 seconds is correctly passed to the _post_json call.

Suggested change

	assert calls[0][1] == {"is_checkpoint_format": True}
	assert calls[0][1] == {"is_checkpoint_format": True}
	assert calls[0][2] == 900.0

[gemini-code-assist]

Instead of dropping the timeout assertion, we should verify that the default timeout of 900.0 seconds is correctly passed to the _post_json call.

Suggested change

	assert len(calls) == 1
	assert calls[0][0] == "finish_weight_update"
	assert calls[0][1] == {}
	assert len(calls) == 1
	assert calls[0][0] == "finish_weight_update"
	assert calls[0][1] == {}
	assert calls[0][2] == 900.0

[knlnguyen1802]

@aoshen02 Let's fix in on main branch

[aoshen02]

PR #22 is now merged into main; reopening against main with broader scope to also restore the production behavior that the test drift was hiding (timeout-env precedence and response-parsing semantics) — see follow-up PR.