apply configs in tests properly

test_libs/pyspec/eth2spec/config/apply_config.py

@@ -5,6 +5,7 @@ presets: Dict[str, Any] = {}
 
 
 # Access to overwrite spec constants based on configuration
+# This is called by the spec module after declaring its globals, and applies the loaded presets.
 def apply_constants_preset(spec_globals: Dict[str, Any]) -> None:
     global presets
     for k, v in presets.items():
@@ -14,6 +15,8 @@ def apply_constants_preset(spec_globals: Dict[str, Any]) -> None:
             spec_globals[k] = v
 
 
+# Load presets from a file. This does not apply the presets.
+# To apply the presets, reload the spec module (it will re-initialize with the presets taken from here).
 def load_presets(configs_path, config_name):
     global presets
     presets = loader.load_presets(configs_path, config_name)

test_libs/pyspec/eth2spec/test/conftest.py

@@ -1,4 +1,5 @@
 from eth2spec.config import apply_config
+from eth2spec.test.context import reload_specs
 
 # We import pytest only when it's present, i.e. when we are running tests.
 # The test-cases themselves can be generated without installing pytest.
@@ -33,3 +34,5 @@ def pytest_addoption(parser):
 def config(request):
     config_name = request.config.getoption("--config")
     apply_config.load_presets('../../configs/', config_name)
+    # now that the presets are loaded, reload the specs to apply them
+    reload_specs()

test_libs/pyspec/eth2spec/test/context.py

@@ -10,8 +10,10 @@ from typing import Any, Callable, Sequence
 
 from importlib import reload
 
-reload(spec_phase0)
-reload(spec_phase1)
+
+def reload_specs():
+    reload(spec_phase0)
+    reload(spec_phase1)
 
 
 def with_custom_state(balances_fn: Callable[[Any], Sequence[int]],