diff --git a/tests/test_filters.py b/tests/test_filters.py
index 38183df..e358746 100644
--- a/tests/test_filters.py
+++ b/tests/test_filters.py
@@ -38,10 +38,34 @@ class TestStringCriterion:
         c = StringCriterion(value="zelda", modifier=Modifier.EQUALS)
         assert c.to_q("name") == Q(name="zelda")
 
+    def test_not_equals(self):
+        c = StringCriterion(value="zelda", modifier=Modifier.NOT_EQUALS)
+        assert c.to_q("name") == ~Q(name="zelda")
+
+    def test_includes(self):
+        c = StringCriterion(value="zelda", modifier=Modifier.INCLUDES)
+        assert c.to_q("name") == Q(name__icontains="zelda")
+
+    def test_excludes(self):
+        c = StringCriterion(value="zelda", modifier=Modifier.EXCLUDES)
+        assert c.to_q("name") == ~Q(name__icontains="zelda")
+
+    def test_matches_regex(self):
+        c = StringCriterion(value="zelda", modifier=Modifier.MATCHES_REGEX)
+        assert c.to_q("name") == Q(name__regex="zelda")
+
+    def test_not_matches_regex(self):
+        c = StringCriterion(value="zelda", modifier=Modifier.NOT_MATCHES_REGEX)
+        assert c.to_q("name") == ~Q(name__regex="zelda")
+
     def test_is_null(self):
         c = StringCriterion(value="", modifier=Modifier.IS_NULL)
         assert c.to_q("name") == Q(name__isnull=True)
 
+    def test_not_null(self):
+        c = StringCriterion(value="", modifier=Modifier.NOT_NULL)
+        assert c.to_q("name") == Q(name__isnull=False)
+
 
 class TestIntCriterion:
     def test_between(self):