[ci] CI coverage tracking

[zhuzilin]

As slime grows, we need more thorough CI coverage for an increasing number of backends, deployment patterns, and training features.
This issue serves as a living index of our existing CI tests so that both users and contributors can quickly see:

• which backends are currently exercised by CI
• which parallelism / optimizer / algorithmic features are being tested
• where coverage gaps still exist

Over time this document should evolve into a compact “CI coverage map” of slime.

Megatron Backend CI

All Megatron-backend CI tests currently check at least the following invariants:

• kl_loss == 0 on step 0
• ppo_kl == 0 on step 0 of each rollout

These are used as sanity checks that the initial policy/value setup and reference policy wiring are correct.

tests/test_quick_start_glm4_9B.py

• tp2, cp2
• 3 steps, rollout 8 × 8, gbs=32
• disaggregated
• algo: GRPO

tests/test_qwen3_30B_A3B.py

• tp4, pp, cp, ep, cpu adam
• 3 steps, rollout 8 × 8, gbs=32
• colocated
• algo:
  • GSPO
  • Routing replay
  • TIS

tests/test_moonlight_16B_A3B.py

• mla, tp4, pp, cp, ep, cpu adam
• 3 steps, rollout 8 × 8, gbs=32
• colocated

tests/test_qwen3_4B_ppo.py

• tp4, pp, cp, ep, cpu adam
• 3 steps, rollout 8 × 8, gbs=32
• colocated
• algo:
  • PPO

tests/test_qwen2.5_0.5B_gsm8k.py

• no parallism
• algo: grpo

tests/test_qwen2.5_0.5B_gsm8k_async.py

• no parallism
• algo:
  • GSPO
  • true on-policy

FSDP Backend CI

All FSDP-backend CI tests share a common set of checks (e.g., basic training sanity, loss decreasing, etc.).
More detailed invariants will be documented here as they are standardized across tests.

TODO: enumerate and unify the exact common assertions for FSDP tests.

tests/test_qwen3_4B_fsdp_true_on_policy.py

• algo: grpo

tests/test_qwen3_0.6B_fsdp_distributed.py

tests/test_qwen3_0.6B_fsdp_colocated_2xGPU.py

---

TODO

• PPO
• rollout routing replay
• deterministic training
• distributed post
• partial rollout
• fault tolerance
• mtp training

[ParagEkbote]

pytest-cov is a useful plugin of pytest that can be used to track the coverage of tests. Would you like to see this included?

cc: @zhuzilin

[zhuzilin]

@ParagEkbote Thank you for the recommendation. We are still in the process of adding e2e tests and will give pytest-conv a try when we start to add more unitests.