diff --git a/test_libs/pyspec/eth2spec/fuzzing/__init__.py b/test_libs/pyspec/eth2spec/fuzzing/__init__.py
new file mode 100644
index 000000000..e69de29bb
diff --git a/test_libs/pyspec/eth2spec/fuzzing/decoder.py b/test_libs/pyspec/eth2spec/fuzzing/decoder.py
new file mode 100644
index 000000000..a5d3dfd97
--- /dev/null
+++ b/test_libs/pyspec/eth2spec/fuzzing/decoder.py
@@ -0,0 +1,84 @@
+from eth2spec.utils.ssz import ssz_typing as spec_ssz
+import ssz
+
+
+def translate_typ(typ) -> ssz.BaseSedes:
+    """
+    Translates a spec type to a Py-SSZ type description (sedes).
+    :param typ: The spec type, a class.
+    :return: The Py-SSZ equivalent.
+    """
+    if spec_ssz.is_container_type(typ):
+        return ssz.Container(
+            [translate_typ(field_typ) for (field_name, field_typ) in typ.get_fields()])
+    elif spec_ssz.is_bytesn_type(typ):
+        return ssz.ByteVector(typ.length)
+    elif spec_ssz.is_bytes_type(typ):
+        return ssz.ByteList()
+    elif spec_ssz.is_vector_type(typ):
+        return ssz.Vector(translate_typ(spec_ssz.read_vector_elem_type(typ)), typ.length)
+    elif spec_ssz.is_list_type(typ):
+        return ssz.List(translate_typ(spec_ssz.read_list_elem_type(typ)))
+    elif spec_ssz.is_bool_type(typ):
+        return ssz.boolean
+    elif spec_ssz.is_uint_type(typ):
+        size = spec_ssz.uint_byte_size(typ)
+        if size == 1:
+            return ssz.uint8
+        elif size == 2:
+            return ssz.uint16
+        elif size == 4:
+            return ssz.uint32
+        elif size == 8:
+            return ssz.uint64
+        elif size == 16:
+            return ssz.uint128
+        elif size == 32:
+            return ssz.uint256
+        else:
+            raise TypeError("invalid uint size")
+    else:
+        raise TypeError("Type not supported: {}".format(typ))
+
+
+def translate_value(value, typ):
+    """
+    Translate a value output from Py-SSZ deserialization into the given spec type.
+    :param value: The PySSZ value
+    :param typ: The type from the spec to translate into
+    :return: the translated value
+    """
+    if spec_ssz.is_uint_type(typ):
+        size = spec_ssz.uint_byte_size(typ)
+        if size == 1:
+            return spec_ssz.uint8(value)
+        elif size == 2:
+            return spec_ssz.uint16(value)
+        elif size == 4:
+            return spec_ssz.uint32(value)
+        elif size == 8:
+            # uint64 is default (TODO this is changing soon)
+            return value
+        elif size == 16:
+            return spec_ssz.uint128(value)
+        elif size == 32:
+            return spec_ssz.uint256(value)
+        else:
+            raise TypeError("invalid uint size")
+    elif spec_ssz.is_list_type(typ):
+        elem_typ = spec_ssz.read_elem_type(typ)
+        return [translate_value(elem, elem_typ) for elem in value]
+    elif spec_ssz.is_bool_type(typ):
+        return value
+    elif spec_ssz.is_vector_type(typ):
+        elem_typ = spec_ssz.read_elem_type(typ)
+        return typ(*(translate_value(elem, elem_typ) for elem in value))
+    elif spec_ssz.is_bytesn_type(typ):
+        return typ(value)
+    elif spec_ssz.is_bytes_type(typ):
+        return value
+    elif spec_ssz.is_container_type(typ):
+        return typ(**{f_name: translate_value(f_val, f_typ) for (f_name, f_val, f_typ)
+                      in zip(typ.get_field_names(), value, typ.get_field_types())})
+    else:
+        raise TypeError("Type not supported: {}".format(typ))
diff --git a/test_libs/pyspec/eth2spec/fuzzing/test_decoder.py b/test_libs/pyspec/eth2spec/fuzzing/test_decoder.py
new file mode 100644
index 000000000..26ee6e913
--- /dev/null
+++ b/test_libs/pyspec/eth2spec/fuzzing/test_decoder.py
@@ -0,0 +1,33 @@
+from eth2spec.fuzzing.decoder import translate_typ, translate_value
+from eth2spec.phase0 import spec
+from eth2spec.utils.ssz import ssz_impl as spec_ssz_impl
+from random import Random
+from eth2spec.debug import random_value
+
+
+def test_decoder():
+    rng = Random(123)
+
+    # check these types only, Block covers a lot of operation types already.
+    for typ in [spec.BeaconBlock, spec.BeaconState, spec.IndexedAttestation, spec.AttestationDataAndCustodyBit]:
+        # create a random pyspec value
+        original = random_value.get_random_ssz_object(rng, typ, 100, 10,
+                                                      mode=random_value.RandomizationMode.mode_random,
+                                                      chaos=True)
+        # serialize it, using pyspec
+        pyspec_data = spec_ssz_impl.serialize(original)
+        # get the py-ssz type for it
+        block_sedes = translate_typ(typ)
+        # try decoding using the py-ssz type
+        raw_value = block_sedes.deserialize(pyspec_data)
+
+        # serialize it using py-ssz
+        pyssz_data = block_sedes.serialize(raw_value)
+        # now check if the serialized form is equal. If so, we confirmed decoding and encoding to work.
+        assert pyspec_data == pyssz_data
+
+        # now translate the py-ssz value in a pyspec-value
+        block = translate_value(raw_value, typ)
+
+        # and see if the hash-tree-root of the original matches the hash-tree-root of the decoded & translated value.
+        assert spec_ssz_impl.hash_tree_root(original) == spec_ssz_impl.hash_tree_root(block)
diff --git a/test_libs/pyspec/requirements.txt b/test_libs/pyspec/requirements.txt
index 3b38930bd..2de2aa84b 100644
--- a/test_libs/pyspec/requirements.txt
+++ b/test_libs/pyspec/requirements.txt
@@ -3,3 +3,4 @@ eth-typing>=2.1.0,<3.0.0
 pycryptodome==3.7.3
 py_ecc>=1.6.0
 typing_inspect==0.4.0
+ssz==0.1.0a10
diff --git a/test_libs/pyspec/setup.py b/test_libs/pyspec/setup.py
index e99b911ee..3856640ab 100644
--- a/test_libs/pyspec/setup.py
+++ b/test_libs/pyspec/setup.py
@@ -9,6 +9,7 @@ setup(
         "eth-typing>=2.1.0,<3.0.0",
         "pycryptodome==3.7.3",
         "py_ecc>=1.6.0",
-        "typing_inspect==0.4.0"
+        "typing_inspect==0.4.0",
+        "ssz==0.1.0a10"
     ]
 )