diff --git a/tests/core/pyspec/eth2spec/test/context.py b/tests/core/pyspec/eth2spec/test/context.py
index 2a6f2e324a..0ba4a20f36 100644
--- a/tests/core/pyspec/eth2spec/test/context.py
+++ b/tests/core/pyspec/eth2spec/test/context.py
@@ -2,19 +2,17 @@
 from copy import deepcopy
 from dataclasses import dataclass
 from eth_utils import encode_hex
+import importlib
 
-from eth2spec.phase0 import mainnet as spec_phase0_mainnet, minimal as spec_phase0_minimal
-from eth2spec.altair import mainnet as spec_altair_mainnet, minimal as spec_altair_minimal
-from eth2spec.merge import mainnet as spec_merge_mainnet, minimal as spec_merge_minimal
 from eth2spec.utils import bls
 
 from .exceptions import SkippedTest
 from .helpers.constants import (
-    PHASE0, ALTAIR, MERGE, MINIMAL, MAINNET,
+    PHASE0, ALTAIR, MINIMAL,
     ALL_PHASES, FORKS_BEFORE_ALTAIR, FORKS_BEFORE_MERGE,
     ALL_FORK_UPGRADES,
 )
-from .helpers.typing import SpecForkName, PresetBaseName
+from .helpers.typing import SpecForkName
 from .helpers.genesis import create_genesis_state
 from .utils import (
     vector_test,
@@ -64,20 +62,6 @@ class ForkMeta:
     fork_epoch: int
 
 
-spec_targets: Dict[PresetBaseName, Dict[SpecForkName, Spec]] = {
-    MINIMAL: {
-        PHASE0: spec_phase0_minimal,
-        ALTAIR: spec_altair_minimal,
-        MERGE: spec_merge_minimal,
-    },
-    MAINNET: {
-        PHASE0: spec_phase0_mainnet,
-        ALTAIR: spec_altair_mainnet,
-        MERGE: spec_merge_mainnet,
-    },
-}
-
-
 class SpecForks(TypedDict, total=False):
     PHASE0: SpecPhase0
     ALTAIR: SpecAltair
@@ -360,11 +344,31 @@ def decorator(fn):
     return decorator
 
 
+def _get_module(module_path):
+    module_spec = importlib.util.find_spec(module_path)
+    module = importlib.util.module_from_spec(module_spec)
+    loader = importlib.util.LazyLoader(module_spec.loader)
+    module_spec.loader = loader
+    import sys
+    sys.modules[module_path] = module
+    loader.exec_module(module)
+    return module
+
+
+def _get_targets(preset_name: SpecForkName) -> Dict[SpecForkName, Spec]:
+    return {
+        # e.g., eth2spec.phase0.mainnet
+        fork_name: _get_module('eth2spec.' + fork_name + '.' + preset_name)
+        for fork_name in ALL_PHASES
+    }
+
+
 def _get_preset_targets(kw):
     preset_name = DEFAULT_TEST_PRESET
     if 'preset' in kw:
         preset_name = kw.pop('preset')
-    return spec_targets[preset_name]
+
+    return _get_targets(preset_name)
 
 
 def _get_run_phases(phases, kw):
diff --git a/tests/core/pyspec/eth2spec/test/merge/fork_choice/test_on_merge_block.py b/tests/core/pyspec/eth2spec/test/merge/fork_choice/test_on_merge_block.py
index e0703fdf7f..7c52a60bad 100644
--- a/tests/core/pyspec/eth2spec/test/merge/fork_choice/test_on_merge_block.py
+++ b/tests/core/pyspec/eth2spec/test/merge/fork_choice/test_on_merge_block.py
@@ -1,9 +1,10 @@
 from eth2spec.utils.ssz.ssz_typing import uint256
 from eth2spec.test.exceptions import BlockNotFoundException
-from eth2spec.test.context import spec_state_test, with_phases, MERGE
+from eth2spec.test.context import spec_state_test, with_phases
 from eth2spec.test.helpers.block import (
     build_empty_block_for_next_slot,
 )
+from eth2spec.test.helpers.constants import MERGE
 from eth2spec.test.helpers.fork_choice import (
     get_genesis_forkchoice_store_and_block,
     on_tick_and_append_step,
diff --git a/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py b/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py
index 9cd388698d..cb4b0c4ba6 100644
--- a/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py
+++ b/tests/core/pyspec/eth2spec/test/merge/genesis/test_initialization.py
@@ -1,12 +1,14 @@
 from eth2spec.test.context import (
-    MERGE,
     single_phase,
     spec_test,
     with_presets,
     with_phases,
     with_merge_and_later,
 )
-from eth2spec.test.helpers.constants import MINIMAL
+from eth2spec.test.helpers.constants import (
+    MERGE,
+    MINIMAL,
+)
 from eth2spec.test.helpers.deposits import (
     prepare_full_genesis_deposits,
 )
diff --git a/tests/core/pyspec/eth2spec/test/phase0/fork_choice/test_ex_ante.py b/tests/core/pyspec/eth2spec/test/phase0/fork_choice/test_ex_ante.py
index b3a8b38fb2..3995536000 100644
--- a/tests/core/pyspec/eth2spec/test/phase0/fork_choice/test_ex_ante.py
+++ b/tests/core/pyspec/eth2spec/test/phase0/fork_choice/test_ex_ante.py
@@ -1,5 +1,4 @@
 from eth2spec.test.context import (
-    MAINNET,
     spec_configured_state_test,
     spec_state_test,
     with_all_phases,
@@ -12,6 +11,7 @@
 from eth2spec.test.helpers.block import (
     build_empty_block,
 )
+from eth2spec.test.helpers.constants import MAINNET
 from eth2spec.test.helpers.fork_choice import (
     get_genesis_forkchoice_store_and_block,
     on_tick_and_append_step,