Add finality tests to test vectors

tests/formats/finality/README.md

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+# Finality tests
+
+The aim of the tests for the finality rules.
+
+- [`finality`](./finality.md): transitions triggered by one or more blocks.
+
+## Test case format
+
+### `meta.yaml`
+
+```yaml
+description: string    -- Optional. Description of test case, purely for debugging purposes.
+bls_setting: int       -- see general test-format spec.
+blocks_count: int      -- the number of blocks processed in this test.
+```
+
+### `pre.yaml`
+
+A YAML-encoded `BeaconState`, the state before running the block transitions.
+
+Also available as `pre.ssz`.
+
+
+### `blocks_<index>.yaml`
+
+A series of files, with `<index>` in range `[0, blocks_count)`. Blocks need to be processed in order,
+ following the main transition function (i.e. process slot and epoch transitions in between blocks as normal)
+
+Each file is a YAML-encoded `SignedBeaconBlock`.
+
+Each block is also available as `blocks_<index>.ssz`
+
+### `post.yaml`
+
+A YAML-encoded `BeaconState`, the state after applying the block transitions.
+
+Also available as `post.ssz`.
+
+
+## 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.

tests/generators/finality/README.md

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+# Finality tests
+
+Finality tests cover regular state-transitions in a common block-list format to test finality rules.
+
+Information on the format of the tests can be found in the [finality test formats documentation](../../formats/finality/README.md).

tests/generators/finality/main.py

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+from typing import Iterable
+from importlib import reload
+
+from gen_base import gen_runner, gen_typing
+from gen_from_tests.gen import generate_from_tests
+
+from eth2spec.test.context import PHASE0
+from eth2spec.test.phase0.finality import test_finality
+from eth2spec.config import config_util
+from eth2spec.phase0 import spec as spec_phase0
+from eth2spec.phase1 import spec as spec_phase1
+
+
+def create_provider(handler_name: str, tests_src, config_name: str) -> gen_typing.TestProvider:
+
+    def prepare_fn(configs_path: str) -> str:
+        config_util.prepare_config(configs_path, config_name)
+        reload(spec_phase0)
+        reload(spec_phase1)
+        return config_name
+
+    def cases_fn() -> Iterable[gen_typing.TestCase]:
+        return generate_from_tests(
+            runner_name='finality',
+            handler_name=handler_name,
+            src=tests_src,
+            fork_name=PHASE0,
+        )
+
+    return gen_typing.TestProvider(prepare=prepare_fn, make_cases=cases_fn)
+
+
+if __name__ == "__main__":
+    gen_runner.run_generator("finality", [
+        create_provider('finality', test_finality, 'minimal'),
+        create_provider('finality', test_finality, 'mainnet'),
+    ])

tests/generators/finality/requirements.txt

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+../../core/gen_helpers
+../../../