test_validation

CPU-only unit tests for :mod:fastvideo.train.callbacks.validation.

Covers the parts of ValidationCallback that don't need a real pipeline or distributed init:

• constructor type coercions and defaults,
• on_validation_begin gating logic (every_steps + modulo),
• _find_ema_callback lookup via _callback_dict,
• state_dict / load_state_dict rng round-trip.

The heavy _run_validation path needs a real diffusion pipeline plus distributed init and is exercised by Phase ⅔ tests.

Classes