diff --git a/test/common/functions.py b/test/common/functions.py
index 1f36e69fe..3c37aec61 100644
--- a/test/common/functions.py
+++ b/test/common/functions.py
@@ -1,9 +1,18 @@
 from amaranth import *
+from typing import TYPE_CHECKING, Generator, Any, TypeAlias, TypeVar, Union
 from coreblocks.utils._typing import RecordValueDict, RecordIntDict
-from .infrastructure import TestGen
+from amaranth.hdl.ast import Statement
+from amaranth.sim.core import Command
 
+if TYPE_CHECKING:
+    from .infrastructure import CoreblockCommand
 
-def set_inputs(values: RecordValueDict, field: Record) -> TestGen[None]:
+
+T = TypeVar("T")
+TestGen: TypeAlias = Generator[Union[Command, Value, Statement, "CoreblockCommand", None], Any, T]
+
+
+def set_inputs(values: RecordValueDict, field: Record) -> "TestGen[None]":
     for name, value in values.items():
         if isinstance(value, dict):
             yield from set_inputs(value, getattr(field, name))
@@ -11,7 +20,7 @@ def set_inputs(values: RecordValueDict, field: Record) -> TestGen[None]:
             yield getattr(field, name).eq(value)
 
 
-def get_outputs(field: Record) -> TestGen[RecordIntDict]:
+def get_outputs(field: Record) -> "TestGen[RecordIntDict]":
     # return dict of all signal values in a record because amaranth's simulator can't read all
     # values of a Record in a single yield - it can only read Values (Signals)
     result = {}
diff --git a/test/common/infrastructure.py b/test/common/infrastructure.py
index 6c0a1a271..4eb9e3eac 100644
--- a/test/common/infrastructure.py
+++ b/test/common/infrastructure.py
@@ -3,12 +3,11 @@
 import unittest
 import functools
 from contextlib import contextmanager, nullcontext
-from typing import TypeVar, Generic, Type, TypeGuard, Any, Union, Callable, cast, Generator, TypeAlias
+from typing import TypeVar, Generic, Type, TypeGuard, Any, Union, Callable, cast, TypeAlias
 from amaranth import *
 from amaranth.sim import *
-from amaranth.hdl.ast import Statement
-from amaranth.sim.core import Command
 from .testbenchio import TestbenchIO
+from .functions import TestGen
 from ..gtkw_extension import write_vcd_ext
 from transactron import Method
 from transactron.lib import AdapterTrans
@@ -16,8 +15,7 @@
 from coreblocks.utils import ModuleConnector, HasElaborate, auto_debug_signals, HasDebugSignals
 
 T = TypeVar("T")
-_T_nested_collection = T | list["_T_nested_collection[T]"] | dict[str, "_T_nested_collection[T]"]
-TestGen: TypeAlias = Generator[Command | Value | Statement | "CoreblockCommand" | None, Any, T]
+_T_nested_collection: TypeAlias = T | list["_T_nested_collection[T]"] | dict[str, "_T_nested_collection[T]"]
 
 
 def guard_nested_collection(cont: Any, t: Type[T]) -> TypeGuard[_T_nested_collection[T]]: