diff --git a/vermouth/tests/test_water_bias.py b/vermouth/tests/test_water_bias.py
new file mode 100644
index 000000000..67daed9e7
--- /dev/null
+++ b/vermouth/tests/test_water_bias.py
@@ -0,0 +1,125 @@
+# Copyright 2022 University of Groningen
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+Test for the water bias processor.
+"""
+import pytest
+import networkx as nx
+import vermouth
+from vermouth.rcsu.go_vs_includes import VirtualSideCreator
+from vermouth.system import System
+from vermouth.forcefield import ForceField
+from vermouth.processors.water_bias import ComputeWaterBias
+from vermouth.tests.test_apply_rubber_band import test_molecule
+
+@pytest.mark.parametrize('secstruc, water_bias, idr_regions, expected',
+        ((
+        # only auto-bias single sec struct
+        {1: "H", 2: "H", 3: "H", 4: "H"},
+        {"H": 2.1},
+        [],
+        {0: "H", 3: "H", 5: "H", 6: "H"}
+        ),
+        # only auto-bias two sec struct
+        ({1: "H", 2: "H", 3: "C", 4: "C"},
+        {"H": 2.1, "C": 3.1},
+        [],
+        {0: "H", 3: "H", 5: "C", 6: "C"}
+        ),
+        # only idp bias
+        ({1: "H", 2: "H", 3: "C", 4: "C"},
+        {"idr": 2.1},
+        [(2, 3)],
+        {2: "idr", 3: "idr"}
+        ),
+        # idp and sec struc bias
+        ({1: "H", 2: "H", 3: "C", 4: "C"},
+        {"idr": 1.1, "C": 3.1, "H": 2.1},
+        [(2, 3)],
+        {0: "H", 2: "idr", 3: "idr", 4: "C"}
+        )
+        ))
+def test_assign_residue_water_bias(test_molecule, 
+                                   secstruc,
+                                   water_bias,
+                                   idr_regions,
+                                   expected):
+
+    # set mol meta
+    test_molecule.meta['moltype'] = "molecule_0"
+    # assign some atomtypes; as the molecule is rather
+    # complex we don't need to redo it every time
+    atypes = {0: "P1", 1: "SN4a", 2: "SN4a", 
+              3: "SP1", 4: "C1",
+              5: "TP1", 
+              6: "P1", 7: "SN3a", 8: "SP4"}
+    nx.set_node_attributes(test_molecule, atypes, "atype")
+    sizes = {0: 0.47, 3: 0.41, 5: 0.38, 6: 0.47}
+    # assign residue names
+    resnames = {0: "A", 1: "A", 2: "A", 
+                3: "B", 4: "B",
+                5: "C", 
+                6: "D", 7: "D", 8: "D"}
+    nx.set_node_attributes(test_molecule, resnames, "resname")
+    # assign resids
+    resids = nx.get_node_attributes(test_molecule, "resid")
+    nx.set_node_attributes(test_molecule, resids, "_old_resid")
+    # assign chain ids
+    nx.set_node_attributes(test_molecule, "A", "chain")
+    
+    # make the proper force-field
+    ff = ForceField("test")
+    ff.variables['water_type'] = "W"
+    ff.variables['regular'] = 0.47
+    ff.variables['small'] = 0.41
+    ff.variables['tiny'] = 0.38
+
+    res_graph = vermouth.graph_utils.make_residue_graph(test_molecule)
+    for node in res_graph.nodes:
+        mol_nodes = res_graph.nodes[node]['graph'].nodes
+        block = vermouth.molecule.Block()
+        resname = res_graph.nodes[node]['resname']
+        resid = res_graph.nodes[node]['resid']
+        # assign secondary structure
+        for mol_node in mol_nodes:
+            test_molecule.nodes[mol_node]['cgsecstruct'] = secstruc[resid]
+            block.add_node(test_molecule.nodes[mol_node]['atomname'],
+                           atype=test_molecule.nodes[mol_node]['atype'])
+
+        ff.blocks[resname] = block
+
+
+    # create the system
+    test_molecule._force_field = ff
+    system = System()
+    system.molecules.append(test_molecule)
+
+    # generate the virtual sites
+    VirtualSideCreator().run_system(system)
+
+    processor = ComputeWaterBias(water_bias=water_bias, 
+                                 auto_bias=True, 
+                                 idr_regions=idr_regions)
+    processor.run_system(system)
+    for nb_params in system.gmx_topology_params['nonbond_params']:
+        assert nb_params.atoms[0] == "W"
+        vs_node = nb_params.atoms[1]
+        for vs in system.molecules[0].interactions['virtual_sitesn']:
+            if vs.atoms[0] == vs_node:
+                bb_node = vs.atoms[1]
+                water_eps = water_bias[expected[bb_node]]
+                water_sig = sizes[bb_node]
+                assert water_eps == nb_params.epsilon
+                assert water_sig == nb_params.sigma