diff --git a/tests/frontier/opcodes/test_calldatacopy.py b/tests/frontier/opcodes/test_calldatacopy.py
index 2b0c1d6261..e84eb000b4 100644
--- a/tests/frontier/opcodes/test_calldatacopy.py
+++ b/tests/frontier/opcodes/test_calldatacopy.py
@@ -8,13 +8,12 @@
     Account,
     Alloc,
     Bytecode,
-    Environment,
-    Hash,
     StateTestFiller,
     Transaction,
 )
 from ethereum_test_tools.vm.opcode import Opcodes as Op
 
+
 @pytest.mark.valid_from("Byzantium")
 @pytest.mark.parametrize(
     "code,tx_data,code_address_storage,to_address_storage",
@@ -35,8 +34,12 @@
                 + Op.STOP
             ),
             b"\x00",
-            Account(storage={0x00: 0x3456000000000000000000000000000000000000000000000000000000000000}),
-            Account(storage={0x00: 0x3456000000000000000000000000000000000000000000000000000000000000}),
+            Account(
+                storage={0x00: 0x3456000000000000000000000000000000000000000000000000000000000000}
+            ),
+            Account(
+                storage={0x00: 0x3456000000000000000000000000000000000000000000000000000000000000}
+            ),
         ),
         (
             (
@@ -54,14 +57,12 @@
                 + Op.STOP
             ),
             b"\x01",
-            Account(storage={
-                        0x00: 0x3400000000000000000000000000000000000000000000000000000000000000
-                    },
-                ),
-            Account(storage={
-                        0x00: 0x3400000000000000000000000000000000000000000000000000000000000000
-                    },
-                ),
+            Account(
+                storage={0x00: 0x3400000000000000000000000000000000000000000000000000000000000000},
+            ),
+            Account(
+                storage={0x00: 0x3400000000000000000000000000000000000000000000000000000000000000},
+            ),
         ),
         (
             (
@@ -80,11 +81,11 @@
             ),
             b"\x02",
             Account(
-                    storage={0x00: 0x00},
-                ),
+                storage={0x00: 0x00},
+            ),
             Account(
-                    storage={0x00: 0x00},
-                ),
+                storage={0x00: 0x00},
+            ),
         ),
         (
             (
@@ -103,11 +104,11 @@
             ),
             b"\x03",
             Account(
-                    storage={0x00: 0x00},
-                ),
+                storage={0x00: 0x00},
+            ),
             Account(
-                    storage={0x00: 0x00},
-                ),
+                storage={0x00: 0x00},
+            ),
         ),
         (
             (
@@ -209,6 +210,11 @@ def test_calldatacopy(
     code_address_storage: Account,
     to_address_storage: Account,
 ):
+    """
+    Test `CALLDATACOPY` opcode.
+
+    Based on https://github.com/ethereum/tests/blob/develop/src/GeneralStateTestsFiller/VMTests/vmTests/calldatacopyFiller.yml
+    """
     code_address = pre.deploy_contract(code)
     to = pre.deploy_contract(
         code=(