docs for sanity tests

specs/test_formats/sanity/README.md

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+# Sanity tests
+
+The aim of the sanity tests is to set a base-line on what really needs to pass, i.e. the essentials.
+
+There are two handlers, documented individually:
+- [`slots`](./slots.md): transitions of one or more slots (and epoch transitions within)
+- [`blocks`](./blocks.md): transitions triggered by one or more blocks

specs/test_formats/sanity/blocks.md

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+# Sanity blocks testing
+
+Sanity tests to cover a series of one or more blocks being processed, aiming to cover common changes.
+
+## Test case format
+
+```yaml
+description: string    -- description of test case, purely for debugging purposes
+bls_required: bool     -- optional, true if the test validity is strictly dependent on BLS being ON. False otherwise.
+bls_ignored: bool      -- optional, true if the test validity is strictly dependent on BLS being OFF. False otherwise.
+pre: BeaconState       -- state before running through the transitions triggered by the blocks.
+blocks: [BeaconBlock]  -- blocks to process, in given order, following the main transition function (i.e. process slot and epoch transitions in between blocks as normal)
+post: BeaconState      -- state after applying all the transitions triggered by the blocks.
+```
+
+## Condition
+
+The resulting state should match the expected `post` state, or if the `post` state is left blank,
+ the handler should reject the series of blocks as invalid.

specs/test_formats/sanity/slots.md

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+# Sanity slots testing
+
+Sanity tests to cover a series of one or more empty-slot transitions being processed, aiming to cover common changes.
+
+## Test case format
+
+```yaml
+description: string    -- description of test case, purely for debugging purposes
+bls_required: bool     -- optional, true if the test validity is strictly dependent on BLS being ON. False otherwise.
+bls_ignored: bool      -- optional, true if the test validity is strictly dependent on BLS being OFF. False otherwise.
+pre: BeaconState       -- state before running through the transitions.
+slots: N               -- amount of slots to process, N being a positive numer.
+post: BeaconState      -- state after applying all the transitions.
+```
+
+The transition with pure time, no blocks, is known as `state_transition_to(state, slot)` in the spec.
+This runs state-caching (pure slot transition) and epoch processing (every E slots).
+
+To process the data, call `state_transition_to(pre, pre.slot + N)`. And see if `pre` mutated into the equivalent of `post`.
+
+
+## Condition
+
+The resulting state should match the expected `post` state.