diff --git a/.github/workflows/CI.yaml b/.github/workflows/CI.yaml
index d2f84fb..64c6248 100644
--- a/.github/workflows/CI.yaml
+++ b/.github/workflows/CI.yaml
@@ -7,11 +7,6 @@ on:
   pull_request:
     branches:
       - "main"
-  #schedule:
-  #  # Nightly tests run on master by default:
-  #  #   Scheduled workflows run on the latest commit on the default or base branch.
-  #  #   (from https://help.github.com/en/actions/reference/events-that-trigger-workflows#scheduled-events-schedule)
-  #  - cron: "0 0 * * *"
 
 jobs:
   test:
@@ -19,8 +14,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest] #[ubuntu-latest, macOS-latest]
-        python-version: ['3.10'] #[3.7, 3.8, 3.9, 3.10, 3.11, 3.12]
+        os: [ubuntu-latest]
+        python-version: ['3.10']
 
     steps:
     - uses: actions/checkout@v4
@@ -32,10 +27,8 @@ jobs:
         df -h
         ulimit -a
 
-
     - uses: mamba-org/setup-micromamba@v1
       with:
-        #python-version: ${{ matrix.python-version }}
         create-args: >-
           python=${{ matrix.python-version }}
         init-shell: bash
@@ -47,12 +40,10 @@ jobs:
         pip install . --no-deps
         conda list
 
-
     - name: Run tests
       shell: bash -l {0}
       run: |
-        pip install . --no-deps
-        pytest -v --color=yes --cov=serenityff --cov-report=xml --run-slow serenityff/charge/tests/ tests/
+        pytest -v --color=yes --cov=serenityff --cov-report=xml --run-slow --tier max serenityff/charge/tests/ tests/
 
   analyze:
     name: Analyze
diff --git a/.github/workflows/scheduled.yaml b/.github/workflows/scheduled.yaml
new file mode 100644
index 0000000..f3e85e6
--- /dev/null
+++ b/.github/workflows/scheduled.yaml
@@ -0,0 +1,43 @@
+name: scheduled-tests
+
+on:
+  schedule:
+    - cron: "0 2 * * 6"
+
+jobs:
+  test:
+    name: Run ${{ matrix.env-name }} environment
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - env-name: "min"
+            file: "tree_only_env.yml"
+            mark: "min"
+          - env-name: "med"
+            file: "min_environment.yml"
+            mark: "med"
+          - env-name: "max"
+            file: "environment.yml"
+            mark: "max"
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Conda
+        uses: conda-incubator/setup-miniconda@v3
+        with:
+          activate-environment: test-env
+          environment-file: ${{ matrix.file }}
+
+      - name: End-to-End Install
+        shell: bash -l {0}
+        run: |
+          conda install -y pytest pytest-cov
+          pip install git+https://github.com/rinikerlab/DASH-tree.git@${{ github.sha }}"
+
+      - name: Run Tests
+        shell: bash -l {0}
+        run: |
+          pytest -v --color=yes --cov=serenityff --cov-report=xml --run-slow --tier "${{ matrix.mark }}" serenityff/charge/tests/ tests/
diff --git a/serenityff/charge/tests/test_gnn_extraction.py b/serenityff/charge/tests/test_gnn_extraction.py
index 24438ef..9fc4f69 100644
--- a/serenityff/charge/tests/test_gnn_extraction.py
+++ b/serenityff/charge/tests/test_gnn_extraction.py
@@ -104,6 +104,7 @@ def graph(cwd) -> CustomData:
     )
 
 
+@pytest.mark.max
 def test_getter_setter(explainer) -> None:
     with pytest.raises(TypeError):
         explainer.gnn_explainer = "asdf"
@@ -111,11 +112,13 @@ def test_getter_setter(explainer) -> None:
     return
 
 
+@pytest.mark.max
 def test_load(model, statedict) -> None:
     assert all(a == b for a, b in zip(model.state_dict(), statedict))
     return
 
 
+@pytest.mark.max
 def test_explain_atom(explainer, graph) -> None:
     explainer.gnn_explainer.explain_node(
         node_idx=0,
@@ -150,6 +153,7 @@ def test_explain_atom(explainer, graph) -> None:
     return
 
 
+@pytest.mark.max
 def test_extractor_properties(extractor, model, model_path, statedict_path, explainer) -> None:
     extractor._set_model(model)
     assert isinstance(extractor.model, ChargeCorrectedNodeWiseAttentiveFP)
@@ -166,6 +170,7 @@ def test_extractor_properties(extractor, model, model_path, statedict_path, expl
     assert isinstance(extractor.model, NodeWiseAttentiveFP)
 
 
+@pytest.mark.max
 def test_split_sdf(cwd, sdf_path) -> None:
     Extractor._split_sdf(
         sdf_file=sdf_path,
@@ -178,6 +183,7 @@ def test_split_sdf(cwd, sdf_path) -> None:
     return
 
 
+@pytest.mark.max
 def test_job_id(cwd) -> None:
     with open(f"{cwd}/id.txt", "w") as f:
         f.write("sdcep ab ein \n sdf <12345> saoeb <sd>")
@@ -187,11 +193,13 @@ def test_job_id(cwd) -> None:
     return
 
 
+@pytest.mark.max
 def test_mol_from_sdf(sdf_path):
     mol = mols_from_sdf(sdf_file=sdf_path)[0]
     assert mol.GetNumBonds() == 19
 
 
+@pytest.mark.max
 def test_graph_from_mol(mol, num_atoms, num_bonds, formal_charge, smiles) -> None:
     with pytest.raises(ValueError):
         get_graph_from_mol(mol=mol, index=0, sdf_property_name=None)
@@ -209,6 +217,7 @@ def test_graph_from_mol(mol, num_atoms, num_bonds, formal_charge, smiles) -> Non
     return
 
 
+@pytest.mark.max
 @pytest.mark.parametrize("sdf_prop", [(None), ("MBIScharge")])
 def test_graph_from_mol_no_y(mol, num_atoms, num_bonds, formal_charge, smiles, sdf_prop) -> None:
     graph = get_graph_from_mol(mol=mol, index=0, sdf_property_name=sdf_prop, no_y=True)
@@ -223,6 +232,7 @@ def test_graph_from_mol_no_y(mol, num_atoms, num_bonds, formal_charge, smiles, s
     return
 
 
+@pytest.mark.max
 def test_arg_parser(args, sdf_path, statedict_path) -> None:
     args = Extractor._parse_filenames(args)
     assert args.sdffile == sdf_path
@@ -230,6 +240,7 @@ def test_arg_parser(args, sdf_path, statedict_path) -> None:
     return
 
 
+@pytest.mark.max
 def test_script_writing(cwd) -> None:
     Extractor._write_worker(directory=cwd)
     Extractor._write_cleaner(directory=cwd)
@@ -239,11 +250,13 @@ def test_script_writing(cwd) -> None:
     return
 
 
+@pytest.mark.max
 def test_explainer_initialization(extractor, model) -> None:
     extractor._initialize_expaliner(model=model, epochs=1)
     return
 
 
+@pytest.mark.max
 def test_command_to_shell_file(cwd) -> None:
     command_to_shell_file("echo Hello World", f"{cwd}/test.sh")
     os.path.isfile(f"{cwd}/test.sh")
@@ -253,6 +266,7 @@ def test_command_to_shell_file(cwd) -> None:
     os.remove(f"{cwd}/test.sh")
 
 
+@pytest.mark.max
 def test_csv_handling(cwd, sdf_path, extractor, model):
     extractor._initialize_expaliner(model=model, epochs=1)
     outfile = f"{cwd}/sdftest/combined.csv"
@@ -268,6 +282,7 @@ def test_csv_handling(cwd, sdf_path, extractor, model):
     rmtree(f"{cwd}/sdftest")
 
 
+@pytest.mark.max
 def test_run_extraction_local(extractor, statedict_path, cwd, sdf_path) -> None:
     extractor.run_extraction_local(
         sdf_file=sdf_path,
diff --git a/serenityff/charge/tests/test_gnn_training.py b/serenityff/charge/tests/test_gnn_training.py
index e25177f..e98292d 100644
--- a/serenityff/charge/tests/test_gnn_training.py
+++ b/serenityff/charge/tests/test_gnn_training.py
@@ -85,6 +85,7 @@ def trainer(model, optimizer):
     return trainer
 
 
+@pytest.mark.max
 def test_init_and_forward_model(model, graph) -> None:
     model = model
     model.train()
@@ -99,6 +100,7 @@ def test_init_and_forward_model(model, graph) -> None:
     return
 
 
+@pytest.mark.max
 def test_initialize_trainer(trainer, model, sdf_path, pt_path, statedict_path, model_path, statedict) -> None:
     # test init
     assert trainer.device == device("cuda") if is_available() else device("cpu")
@@ -147,6 +149,7 @@ def test_initialize_trainer(trainer, model, sdf_path, pt_path, statedict_path, m
     return
 
 
+@pytest.mark.max
 def test_prepare_train_data(trainer, sdf_path):
     with pytest.warns(Warning):
         trainer.prepare_training_data()
@@ -158,6 +161,7 @@ def test_prepare_train_data(trainer, sdf_path):
     return
 
 
+@pytest.mark.max
 def test_train_model(trainer, sdf_path) -> None:
     trainer.gen_graphs_from_sdf(sdf_path)
     trainer.prepare_training_data(train_ratio=0.5)
@@ -173,6 +177,7 @@ def test_train_model(trainer, sdf_path) -> None:
     return
 
 
+@pytest.mark.max
 def test_prediction(trainer, graph, molecule) -> None:
 
     a = trainer.predict(graph)
@@ -198,6 +203,7 @@ def test_prediction(trainer, graph, molecule) -> None:
     return
 
 
+@pytest.mark.max
 def test_on_gpu(trainer) -> None:
 
     assert trainer._on_gpu == is_available()
diff --git a/serenityff/charge/tests/test_gnn_utils.py b/serenityff/charge/tests/test_gnn_utils.py
index 20bfe41..fc5d89b 100644
--- a/serenityff/charge/tests/test_gnn_utils.py
+++ b/serenityff/charge/tests/test_gnn_utils.py
@@ -126,6 +126,7 @@ def node_features() -> np.ndarray:
     )
 
 
+@pytest.mark.max
 def test_get_split_numbers() -> None:
     assert [1, 0] == get_split_numbers(N=1, train_ratio=0.5)
     assert [1, 1] == get_split_numbers(N=2, train_ratio=0.5)
@@ -136,6 +137,7 @@ def test_get_split_numbers() -> None:
     return
 
 
+@pytest.mark.max
 def test_random_split(data) -> None:
     train, test = split_data_random(data_list=data, train_ratio=0.5)
     assert len(train) == 6
@@ -143,6 +145,7 @@ def test_random_split(data) -> None:
     return
 
 
+@pytest.mark.max
 def test_kfold_split(data) -> None:
     train1, test1 = split_data_Kfold(data, n_splits=2, split=0)
     train2, test2 = split_data_Kfold(data, n_splits=2, split=1)
@@ -151,6 +154,7 @@ def test_kfold_split(data) -> None:
     return
 
 
+@pytest.mark.max
 def test_initialization() -> None:
     featurizer = Featurizer()
     featurizer = MolecularFeaturizer()
@@ -159,6 +163,7 @@ def test_initialization() -> None:
     return
 
 
+@pytest.mark.max
 def test_one_hot_encode(atoms, allowable_set) -> None:
     assert one_hot_encode(atoms[0].GetSymbol(), allowable_set) == [1.0, 0.0, 0.0]
     assert one_hot_encode(atoms[0].GetSymbol(), allowable_set, include_unknown_set=True) == [1.0, 0.0, 0.0, 0.0]
@@ -166,6 +171,7 @@ def test_one_hot_encode(atoms, allowable_set) -> None:
     return
 
 
+@pytest.mark.max
 def test_hbond_constructor(mol) -> None:
     factory = _ChemicalFeaturesFactory.get_instance()
     import os
@@ -180,12 +186,14 @@ def test_hbond_constructor(mol) -> None:
     return
 
 
+@pytest.mark.max
 def test_H_bonding(mol, atoms) -> None:
     hbond_infos = construct_hydrogen_bonding_info(mol)
     assert get_atom_hydrogen_bonding_one_hot(atoms[11], hbond_infos) == [1.0, 1.0]
     return
 
 
+@pytest.mark.max
 def test_degree(atoms) -> None:
     assert np.where(get_atom_total_degree_one_hot(atoms[20])) == np.array([[1]])
     assert np.where(get_atom_total_degree_one_hot(atoms[11])) == np.array([[2]])
@@ -194,6 +202,7 @@ def test_degree(atoms) -> None:
     return
 
 
+@pytest.mark.max
 def test_atom_feature(mol, atoms, allowable_set) -> None:
     hbond_infos = construct_hydrogen_bonding_info(mol)
     feat = _construct_atom_feature(
@@ -206,6 +215,7 @@ def test_atom_feature(mol, atoms, allowable_set) -> None:
     return
 
 
+@pytest.mark.max
 def test_bond_feat(bonds) -> None:
     np.testing.assert_array_equal(np.where(_construct_bond_feature(bonds[0])), np.array([[3, 4, 5, 6]]))
     np.testing.assert_array_equal(np.where(_construct_bond_feature(bonds[6])), np.array([[0, 4, 6]]))
@@ -214,6 +224,7 @@ def test_bond_feat(bonds) -> None:
     return
 
 
+@pytest.mark.max
 def test_feature_vector_generation(smiles, mol, allowable_set, empty_set) -> None:
     featurizer = MolGraphConvFeaturizer(use_edges=True)
 
@@ -231,6 +242,7 @@ def test_feature_vector_generation(smiles, mol, allowable_set, empty_set) -> Non
     return
 
 
+@pytest.mark.max
 def test_graph_data_basics(node_features, edge_index, edge_features, node_pos_features) -> None:
     # Trigger all __init__() failures.
     with pytest.raises(TypeError):
@@ -255,6 +267,7 @@ def test_graph_data_basics(node_features, edge_index, edge_features, node_pos_fe
     return
 
 
+@pytest.mark.max
 def test_getters(
     graph_data,
     custom_graph_data,
@@ -285,6 +298,7 @@ def test_getters(
     return
 
 
+@pytest.mark.max
 def test_to_pyg(
     custom_graph_data,
     node_features,
@@ -301,6 +315,7 @@ def test_to_pyg(
     return
 
 
+@pytest.mark.max
 def test_custom_data_attributes(custom_data) -> None:
     data = custom_data
     assert data.smiles == "abc"
@@ -321,6 +336,7 @@ def test_custom_data_attributes(custom_data) -> None:
     return
 
 
+@pytest.mark.max
 def test_base_featurizer():
     featurizer = Featurizer()
     datapoints = [1]
@@ -332,6 +348,7 @@ def test_base_featurizer():
     assert np.array_equal(features, np.asarray([np.array([])]))
 
 
+@pytest.mark.max
 def test_molecular_featurizer(mol, smiles):
     featurizer = MolecularFeaturizer()
     featurizer.featurize([mol])
@@ -340,6 +357,7 @@ def test_molecular_featurizer(mol, smiles):
     featurizer.featurize(smiles)
 
 
+@pytest.mark.max
 def test_exceptions():
     with pytest.raises(NotInitializedError):
         raise NotInitializedError("msg")
diff --git a/serenityff/charge/tests/test_off_plugin.py b/serenityff/charge/tests/test_off_plugin.py
index 4d919a0..0a78b31 100644
--- a/serenityff/charge/tests/test_off_plugin.py
+++ b/serenityff/charge/tests/test_off_plugin.py
@@ -88,6 +88,7 @@ def charges_amber():
 chg_atol = 0.4
 
 
+@pytest.mark.med
 def test_handler_functions(handler):
     assert handler.check_handler_compatibility(handler) is None
     assert handler._TAGNAME == "SerenityFFCharge"
@@ -95,6 +96,7 @@ def test_handler_functions(handler):
     assert handler._KWARGS == ["toolkit_registry"]
 
 
+@pytest.mark.med
 def test_off_handler_plugins(force_field_with_plugins, keys):
     keys.append("SerenityFFCharge")
     for key in keys:
@@ -103,6 +105,7 @@ def test_off_handler_plugins(force_field_with_plugins, keys):
         force_field_with_plugins.get_parameter_handler("faulty")
 
 
+@pytest.mark.med
 @pytest.mark.skipif(
     condition=are_in_CI(),
     reason="This test is too slow for CI",
@@ -122,6 +125,7 @@ def test_off_handler_custom(force_field_custom_offxml, keys):
 # ------------------------------------------------
 
 
+@pytest.mark.med
 @pytest.mark.skipif(
     condition=are_in_CI(),
     reason="This test is too slow for CI",
@@ -142,6 +146,7 @@ def test_plugin_charges_get(force_field_with_plugins, molecule, charges_amber, c
     )
 
 
+@pytest.mark.med
 @pytest.mark.skipif(
     condition=are_in_CI(),
     reason="This test is too slow for CI",
@@ -162,6 +167,7 @@ def test_plugin_charges_register(force_field_with_plugins, molecule, handler, ch
     )
 
 
+@pytest.mark.med
 @pytest.mark.skipif(
     condition=are_in_CI(),
     reason="This test is too slow for CI",
diff --git a/tests/conftest.py b/tests/conftest.py
index cc1d77b..e4eca61 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,40 +1,43 @@
-# Copyright (C) 2024-2025 ETH Zurich, Niels Maeder and other DASH contributors.
-
 """Pytest configuration file."""
 
-from collections.abc import Sequence
-
 import pytest
+from collections.abc import Sequence
 
 
 def pytest_addoption(parser: pytest.Parser) -> None:
-    """Add cli option to include slow tests.
-
-    Args:
-        parser (pytest.Parser): pytest parser.
-    """
+    parser.addoption(
+        "--tier",
+        action="store",
+        default="min",
+        choices=("min", "med", "max"),
+        help="Run tests for a specific environment tier.",
+    )
     parser.addoption("--run-slow", action="store_true", default=False, help="Include slow tests.")
 
 
 def pytest_configure(config: pytest.Config) -> None:
-    """Add slow marker to pytest.
-
-    Args:
-        config (pytest.Config): pytest configuration.
-    """
-    config.addinivalue_line("markers", "slow: mark test as slow to run")
+    config.addinivalue_line("markers", "min: expected to pass with tree_ony_env.yml")
+    config.addinivalue_line("markers", "med: expected to pass with min_environment.yml")
+    config.addinivalue_line("markers", "max: expected to pass with environment.yml")
+    config.addinivalue_line("markers", "slow: slow running tests")
 
 
 def pytest_collection_modifyitems(config: pytest.Config, items: Sequence[pytest.Item]) -> None:
-    """Skip slow tests if not included.
-
-    Args:
-        config (pytest.Config): pytest configuration.
-        items (Sequence[pytest.Item]): pytest items.
-    """
-    if config.getoption("--run-slow"):
-        return
-    skip_slow = pytest.mark.skip(reason="need --run-slow option to run.")
+    tier = config.getoption("--tier")
+    run_slow = config.getoption("--run-slow")
+
+    allowed_tiers = {"min"}
+    if tier == "med":
+        allowed_tiers.update({"med"})
+    elif tier == "max":
+        allowed_tiers.update({"med", "max"})
+
     for item in items:
-        if "slow" in item.keywords:
-            item.add_marker(skip_slow)
+        item_tiers = {mark.name for mark in item.iter_markers() if mark.name in {"min", "med", "max"}}
+
+        if item_tiers and not (item_tiers & allowed_tiers):
+            item.add_marker(pytest.mark.skip(reason=f"Test requires higher tier than '{tier}'"))
+            continue
+
+        if "slow" in item.keywords and not run_slow:
+            item.add_marker(pytest.mark.skip(reason="Slow test: use --run-slow to run"))
diff --git a/tests/serenityff/charge/gnn/utils/test_rdkit_helper.py b/tests/serenityff/charge/gnn/utils/test_rdkit_helper.py
index 91ab425..ba77f21 100644
--- a/tests/serenityff/charge/gnn/utils/test_rdkit_helper.py
+++ b/tests/serenityff/charge/gnn/utils/test_rdkit_helper.py
@@ -34,6 +34,7 @@ def sample_mol_missing_prop():
     return mol
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_pt_tensor_success(sample_mol_with_prop):
     """Test successful retrieval of property as a tensor."""
     expected = pt.tensor([1.0, 2.5, -3.0], dtype=pt.float)
@@ -42,6 +43,7 @@ def test_get_mol_prop_as_pt_tensor_success(sample_mol_with_prop):
     assert pt.equal(result, expected)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_pt_tensor_raises_value_error_on_none_prop(
     sample_mol_missing_prop,
 ):
@@ -50,6 +52,7 @@ def test_get_mol_prop_as_pt_tensor_raises_value_error_on_none_prop(
         get_mol_prop_as_pt_tensor(None, sample_mol_missing_prop)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_pt_tensor_raises_value_error_on_missing_prop(
     sample_mol_missing_prop,
 ):
@@ -58,6 +61,7 @@ def test_get_mol_prop_as_pt_tensor_raises_value_error_on_missing_prop(
         get_mol_prop_as_pt_tensor("missing_prop", sample_mol_missing_prop)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_pt_tensor_raises_type_error_on_nan(
     sample_mol_with_nan_prop,
 ):
@@ -66,6 +70,7 @@ def test_get_mol_prop_as_pt_tensor_raises_type_error_on_nan(
         get_mol_prop_as_pt_tensor("test_prop_nan", sample_mol_with_nan_prop)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_np_array_success(sample_mol_with_prop):
     """Test successful retrieval of property as a numpy array."""
     expected = np.array([1.0, 2.5, -3.0])
@@ -74,6 +79,7 @@ def test_get_mol_prop_as_np_array_success(sample_mol_with_prop):
     np.testing.assert_array_equal(result, expected)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_np_array_raises_value_error_on_none_prop(
     sample_mol_missing_prop,
 ):
@@ -82,6 +88,7 @@ def test_get_mol_prop_as_np_array_raises_value_error_on_none_prop(
         get_mol_prop_as_np_array(None, sample_mol_missing_prop)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_np_array_raises_value_error_on_missing_prop(
     sample_mol_missing_prop,
 ):
@@ -90,6 +97,7 @@ def test_get_mol_prop_as_np_array_raises_value_error_on_missing_prop(
         get_mol_prop_as_np_array("missing_prop", sample_mol_missing_prop)
 
 
+@pytest.mark.max
 def test_get_mol_prop_as_np_array_raises_type_error_on_nan(
     sample_mol_with_nan_prop,
 ):
diff --git a/tests/serenityff/charge/utils/test_serenityff_charge_handler.py b/tests/serenityff/charge/utils/test_serenityff_charge_handler.py
index d5d3526..bc57945 100644
--- a/tests/serenityff/charge/utils/test_serenityff_charge_handler.py
+++ b/tests/serenityff/charge/utils/test_serenityff_charge_handler.py
@@ -79,6 +79,7 @@ def molecule() -> Molecule:
     return Molecule.from_smiles("CCO")
 
 
+@pytest.mark.med
 def test_handler_init(handler: SerenityFFChargeHandler) -> None:
     assert handler._TAGNAME == "SerenityFFCharge"
     assert handler._DEPENDENCIES == [
@@ -100,6 +101,7 @@ def test_handler_init(handler: SerenityFFChargeHandler) -> None:
     assert handler.attention_threshold == 10
 
 
+@pytest.mark.med
 def test_singleton() -> None:
     instance1 = SerenityFFChargeHandler(version=0.3)
     instance2 = SerenityFFChargeHandler(version=0.3)
@@ -107,6 +109,7 @@ def test_singleton() -> None:
     assert instance1 is instance2
 
 
+@pytest.mark.med
 def test_loading_off_handler_plugins(
     force_field_custom_offxml: ForceField, force_field_with_plugins: ForceField
 ) -> None:
@@ -117,6 +120,7 @@ def test_loading_off_handler_plugins(
         assert force_field_custom_offxml.get_parameter_handler(key)
 
 
+@pytest.mark.med
 def test_plugin_charges_get_parameter_handler(
     force_field_with_plugins: SerenityFFChargeHandler,
     molecule,
@@ -134,6 +138,7 @@ def test_plugin_charges_get_parameter_handler(
     )
 
 
+@pytest.mark.med
 def test_plugin_charges_register(
     force_field_with_plugins,
     molecule,
@@ -152,6 +157,7 @@ def test_plugin_charges_register(
     )
 
 
+@pytest.mark.med
 def test_custom_force_field_file_charges(force_field_custom_offxml: ForceField, molecule) -> None:
     assert allclose(
         force_field_custom_offxml.get_partial_charges(molecule),