diff --git a/Makefile b/Makefile
index 6586646fd..d00817daf 100644
--- a/Makefile
+++ b/Makefile
@@ -34,10 +34,10 @@ install_test:
 	cd $(PY_SPEC_DIR); python3 -m venv venv; . venv/bin/activate; pip3 install -r requirements.txt;
 
 test: $(PY_SPEC_ALL_TARGETS)
-	cd $(PY_SPEC_DIR); . venv/bin/activate; python -m pytest -m minimal_config .
+	cd $(PY_SPEC_DIR); . venv/bin/activate; python -m pytest .
 
 citest: $(PY_SPEC_ALL_TARGETS)
-	cd $(PY_SPEC_DIR); mkdir -p test-reports/eth2spec; . venv/bin/activate; python -m pytest --junitxml=test-reports/eth2spec/test_results.xml -m minimal_config .
+	cd $(PY_SPEC_DIR); mkdir -p test-reports/eth2spec; . venv/bin/activate; python -m pytest --junitxml=test-reports/eth2spec/test_results.xml .
 
 # "make pyspec" to create the pyspec for all phases.
 pyspec: $(PY_SPEC_ALL_TARGETS)
diff --git a/test_libs/pyspec/README.md b/test_libs/pyspec/README.md
index b9bf86220..df1834210 100644
--- a/test_libs/pyspec/README.md
+++ b/test_libs/pyspec/README.md
@@ -38,7 +38,7 @@ Install dependencies:
 ```bash
 python3 -m venv venv
 . venv/bin/activate
-pip3 install -r requirements.txt
+pip3 install -r requirements-testing.txt
 ```
 Note: make sure to run `make -B pyspec` from the root of the specs repository,
  to build the parts of the pyspec module derived from the markdown specs.
@@ -46,7 +46,7 @@ The `-B` flag may be helpful to force-overwrite the `pyspec` output after you ma
 
 Run the tests:
 ```
-pytest -m minimal_config .
+pytest --config=minimal
 ```
 
 
diff --git a/test_libs/pyspec/requirements-testing.txt b/test_libs/pyspec/requirements-testing.txt
new file mode 100644
index 000000000..388a878a9
--- /dev/null
+++ b/test_libs/pyspec/requirements-testing.txt
@@ -0,0 +1,3 @@
+-r requirements.txt
+pytest>=3.6,<3.7
+../config_helpers
diff --git a/test_libs/pyspec/requirements.txt b/test_libs/pyspec/requirements.txt
index 3296ef807..78d41708d 100644
--- a/test_libs/pyspec/requirements.txt
+++ b/test_libs/pyspec/requirements.txt
@@ -2,4 +2,3 @@ eth-utils>=1.3.0,<2
 eth-typing>=2.1.0,<3.0.0
 pycryptodome==3.7.3
 py_ecc>=1.6.0
-pytest>=3.6,<3.7
diff --git a/test_libs/pyspec/tests/README.md b/test_libs/pyspec/tests/README.md
deleted file mode 100644
index e69de29bb..000000000
diff --git a/test_libs/pyspec/tests/conftest.py b/test_libs/pyspec/tests/conftest.py
index bf9b1009b..f6c70d280 100644
--- a/test_libs/pyspec/tests/conftest.py
+++ b/test_libs/pyspec/tests/conftest.py
@@ -1,58 +1,24 @@
 import pytest
 
 from eth2spec.phase0 import spec
+from preset_loader import loader
 
 from .helpers import (
     create_genesis_state,
 )
 
 
-DEFAULT_CONFIG = {}  # no change
-
-MINIMAL_CONFIG = {
-    "SHARD_COUNT": 8,
-    "MIN_ATTESTATION_INCLUSION_DELAY": 2,
-    "TARGET_COMMITTEE_SIZE": 4,
-    "SLOTS_PER_EPOCH": 8,
-    "SLOTS_PER_HISTORICAL_ROOT": 64,
-    "LATEST_RANDAO_MIXES_LENGTH": 64,
-    "LATEST_ACTIVE_INDEX_ROOTS_LENGTH": 64,
-    "LATEST_SLASHED_EXIT_LENGTH": 64,
-}
-
-
-def overwrite_spec_config(config):
-    for field in config:
-        setattr(spec, field, config[field])
-        if field == "LATEST_RANDAO_MIXES_LENGTH":
-            spec.BeaconState.fields['latest_randao_mixes'][1] = config[field]
-        elif field == "SHARD_COUNT":
-            spec.BeaconState.fields['current_crosslinks'][1] = config[field]
-            spec.BeaconState.fields['previous_crosslinks'][1] = config[field]
-        elif field == "SLOTS_PER_HISTORICAL_ROOT":
-            spec.BeaconState.fields['latest_block_roots'][1] = config[field]
-            spec.BeaconState.fields['latest_state_roots'][1] = config[field]
-            spec.HistoricalBatch.fields['block_roots'][1] = config[field]
-            spec.HistoricalBatch.fields['state_roots'][1] = config[field]
-        elif field == "LATEST_ACTIVE_INDEX_ROOTS_LENGTH":
-            spec.BeaconState.fields['latest_active_index_roots'][1] = config[field]
-        elif field == "LATEST_SLASHED_EXIT_LENGTH":
-            spec.BeaconState.fields['latest_slashed_balances'][1] = config[field]
-
-
-@pytest.fixture(
-    params=[
-        pytest.param(MINIMAL_CONFIG, marks=pytest.mark.minimal_config),
-        DEFAULT_CONFIG,
-    ]
-)
-def config(request):
-    return request.param
+def pytest_addoption(parser):
+    parser.addoption(
+        "--config", action="store", default="minimal", help="config: make the pyspec use the specified configuration"
+    )
 
 
 @pytest.fixture(autouse=True)
-def overwrite_config(config):
-    overwrite_spec_config(config)
+def config(request):
+    config_name = request.config.getoption("--config")
+    presets = loader.load_presets('../../configs/', config_name)
+    spec.apply_constants_preset(presets)
 
 
 @pytest.fixture
diff --git a/test_libs/pyspec/tests/helpers.py b/test_libs/pyspec/tests/helpers.py
index d181dadfe..a728a6acc 100644
--- a/test_libs/pyspec/tests/helpers.py
+++ b/test_libs/pyspec/tests/helpers.py
@@ -118,6 +118,7 @@ def create_genesis_state(num_validators, deposit_data_leaves=None):
 def build_empty_block_for_next_slot(state):
     empty_block = BeaconBlock()
     empty_block.slot = state.slot + 1
+    empty_block.body.eth1_data.deposit_count = state.deposit_index
     previous_block_header = deepcopy(state.latest_block_header)
     if previous_block_header.state_root == spec.ZERO_HASH:
         previous_block_header.state_root = state.hash_tree_root()