diff --git a/graphene_django/filter/tests/test_in_filter.py b/graphene_django/filter/tests/test_in_filter.py
index 3d4034eaa..7bbee65a7 100644
--- a/graphene_django/filter/tests/test_in_filter.py
+++ b/graphene_django/filter/tests/test_in_filter.py
@@ -1,9 +1,11 @@
 import pytest
 
+from django_filters import FilterSet
+from django_filters import rest_framework as filters
 from graphene import ObjectType, Schema
 from graphene.relay import Node
 from graphene_django import DjangoObjectType
-from graphene_django.tests.models import Pet
+from graphene_django.tests.models import Pet, Person
 from graphene_django.utils import DJANGO_FILTER_INSTALLED
 
 pytestmark = []
@@ -28,8 +30,27 @@ class Meta:
         }
 
 
+class PersonFilterSet(FilterSet):
+    class Meta:
+        model = Person
+        fields = {}
+
+    names = filters.BaseInFilter(method="filter_names")
+
+    def filter_names(self, qs, name, value):
+        return qs.filter(name__in=value)
+
+
+class PersonNode(DjangoObjectType):
+    class Meta:
+        model = Person
+        interfaces = (Node,)
+        filterset_class = PersonFilterSet
+
+
 class Query(ObjectType):
     pets = DjangoFilterConnectionField(PetNode)
+    people = DjangoFilterConnectionField(PersonNode)
 
 
 def test_string_in_filter():
@@ -61,6 +82,33 @@ def test_string_in_filter():
     ]
 
 
+def test_string_in_filter_with_filterset_class():
+    """Test in filter on a string field with a custom filterset class."""
+    Person.objects.create(name="John")
+    Person.objects.create(name="Michael")
+    Person.objects.create(name="Angela")
+
+    schema = Schema(query=Query)
+
+    query = """
+    query {
+        people (names: ["John", "Michael"]) {
+            edges {
+                node {
+                    name
+                }
+            }
+        }
+    }
+    """
+    result = schema.execute(query)
+    assert not result.errors
+    assert result.data["people"]["edges"] == [
+        {"node": {"name": "John"}},
+        {"node": {"name": "Michael"}},
+    ]
+
+
 def test_int_in_filter():
     """
     Test in filter on an integer field.
diff --git a/graphene_django/filter/utils.py b/graphene_django/filter/utils.py
index 0245f166f..5d3f4f4c8 100644
--- a/graphene_django/filter/utils.py
+++ b/graphene_django/filter/utils.py
@@ -17,6 +17,7 @@ def get_filtering_args_from_filterset(filterset_class, type):
     model = filterset_class._meta.model
     for name, filter_field in filterset_class.base_filters.items():
         form_field = None
+        filter_type = filter_field.lookup_expr
 
         if name in filterset_class.declared_filters:
             # Get the filter field from the explicitly declared filter
@@ -25,7 +26,6 @@ def get_filtering_args_from_filterset(filterset_class, type):
         else:
             # Get the filter field with no explicit type declaration
             model_field = get_model_field(model, filter_field.field_name)
-            filter_type = filter_field.lookup_expr
             if filter_type != "isnull" and hasattr(model_field, "formfield"):
                 form_field = model_field.formfield(
                     required=filter_field.extra.get("required", False)
@@ -38,14 +38,14 @@ def get_filtering_args_from_filterset(filterset_class, type):
 
             field = convert_form_field(form_field)
 
-            if filter_type in ["in", "range"]:
-                # Replace CSV filters (`in`, `range`) argument type to be a list of the same type as the field.
-                # See comments in `replace_csv_filters` method for more details.
-                field = List(field.get_type())
+        if filter_type in ["in", "range"]:
+            # Replace CSV filters (`in`, `range`) argument type to be a list of
+            # the same type as the field.  See comments in
+            # `replace_csv_filters` method for more details.
+            field = List(field.get_type())
 
         field_type = field.Argument()
         field_type.description = str(filter_field.label) if filter_field.label else None
-
         args[name] = field_type
 
     return args
@@ -78,10 +78,7 @@ def replace_csv_filters(filterset_class):
     """
     for name, filter_field in list(filterset_class.base_filters.items()):
         filter_type = filter_field.lookup_expr
-        if (
-            filter_type in ["in", "range"]
-            and name not in filterset_class.declared_filters
-        ):
+        if filter_type in ["in", "range"]:
             assert isinstance(filter_field, BaseCSVFilter)
             filterset_class.base_filters[name] = Filter(
                 field_name=filter_field.field_name,
diff --git a/graphene_django/tests/models.py b/graphene_django/tests/models.py
index 708fe579a..180acc527 100644
--- a/graphene_django/tests/models.py
+++ b/graphene_django/tests/models.py
@@ -6,6 +6,10 @@
 CHOICES = ((1, "this"), (2, _("that")))
 
 
+class Person(models.Model):
+    name = models.CharField(max_length=30)
+
+
 class Pet(models.Model):
     name = models.CharField(max_length=30)
     age = models.PositiveIntegerField()
diff --git a/graphene_django/tests/test_utils.py b/graphene_django/tests/test_utils.py
index 766032e42..d895f46bf 100644
--- a/graphene_django/tests/test_utils.py
+++ b/graphene_django/tests/test_utils.py
@@ -51,6 +51,7 @@ def runTest(self):
             pass
 
     tc = TestClass()
+    tc._pre_setup()
     tc.setUpClass()
     tc.query("query { }", operation_name="QueryName")
     body = json.loads(post_mock.call_args.args[1])
diff --git a/graphene_django/utils/testing.py b/graphene_django/utils/testing.py
index 22efd8b1a..c783f71bf 100644
--- a/graphene_django/utils/testing.py
+++ b/graphene_django/utils/testing.py
@@ -1,6 +1,7 @@
 import json
+import warnings
 
-from django.test import TestCase, Client
+from django.test import Client, TestCase
 
 DEFAULT_GRAPHQL_URL = "/graphql/"
 
@@ -68,12 +69,6 @@ class GraphQLTestCase(TestCase):
     # URL to graphql endpoint
     GRAPHQL_URL = DEFAULT_GRAPHQL_URL
 
-    @classmethod
-    def setUpClass(cls):
-        super(GraphQLTestCase, cls).setUpClass()
-
-        cls._client = Client()
-
     def query(
         self, query, operation_name=None, input_data=None, variables=None, headers=None
     ):
@@ -101,10 +96,19 @@ def query(
             input_data=input_data,
             variables=variables,
             headers=headers,
-            client=self._client,
+            client=self.client,
             graphql_url=self.GRAPHQL_URL,
         )
 
+    @property
+    def _client(self):
+        warnings.warn(
+            "Using `_client` is deprecated in favour of `client`.",
+            PendingDeprecationWarning,
+            stacklevel=2,
+        )
+        return self.client
+
     def assertResponseNoErrors(self, resp, msg=None):
         """
         Assert that the call went through correctly. 200 means the syntax is ok, if there are no `errors`,
diff --git a/graphene_django/utils/tests/test_testing.py b/graphene_django/utils/tests/test_testing.py
new file mode 100644
index 000000000..df7832130
--- /dev/null
+++ b/graphene_django/utils/tests/test_testing.py
@@ -0,0 +1,24 @@
+import pytest
+
+from .. import GraphQLTestCase
+from ...tests.test_types import with_local_registry
+
+
+@with_local_registry
+def test_graphql_test_case_deprecated_client():
+    """
+    Test that `GraphQLTestCase._client`'s should raise pending deprecation warning.
+    """
+
+    class TestClass(GraphQLTestCase):
+        GRAPHQL_SCHEMA = True
+
+        def runTest(self):
+            pass
+
+    tc = TestClass()
+    tc._pre_setup()
+    tc.setUpClass()
+
+    with pytest.warns(PendingDeprecationWarning):
+        tc._client