make ssz_static output roots to roots.yaml instead of meta

specs/test_formats/ssz_static/core.md

@@ -18,16 +18,14 @@ One can iterate over the handlers, and select the type based on the handler name
 Suites are then the same format, but each specialized in one randomization mode.
 Some randomization modes may only produce a single test case (e.g. the all-zeroes case).
 
-The output parts are: `meta.yaml`, `serialized.ssz`, `value.yaml`
+The output parts are: `roots.yaml`, `serialized.ssz`, `value.yaml`
 
-### `meta.yaml`
-
-For non-container SSZ type:
+### `roots.yaml`
 
 ```yaml
 root: bytes32         -- string, hash-tree-root of the value, hex encoded, with prefix 0x
 signing_root: bytes32 -- string, signing-root of the value, hex encoded, with prefix 0x. 
-                           Optional, present if type is a container and ends with a ``signature`` field.
+                           *Optional*, present if type is a container and ends with a ``signature`` field.
 ```
 
 ### `serialized.ssz`

test_generators/ssz_static/main.py

@@ -21,9 +21,12 @@ def create_test_case(rng: Random, typ, mode: random_value.RandomizationMode, cha
     value = random_value.get_random_ssz_object(rng, typ, MAX_BYTES_LENGTH, MAX_LIST_LENGTH, mode, chaos)
     yield "value", "data", encode.encode(value)
     yield "serialized", "ssz", serialize(value)
-    yield "root", "meta", '0x' + hash_tree_root(value).hex()
-    if hasattr(value, "signature"):
-        yield "signing_root", "meta", '0x' + signing_root(value).hex()
+    roots_data = {
+        "root": '0x' + hash_tree_root(value).hex()
+    }
+    if isinstance(value, Container) and hasattr(value, "signature"):
+        roots_data["signing_root"] = '0x' + signing_root(value).hex()
+    yield "roots", "data", roots_data
 
 
 def get_spec_ssz_types():