diff --git a/setup.py b/setup.py
index d9b1edc..3687e57 100644
--- a/setup.py
+++ b/setup.py
@@ -54,6 +54,7 @@ setup(
         'simplejson',
         'six',
         'stix2-patterns',
+        'stix2-validator',
         'taxii2-client',
     ],
 )
diff --git a/stix2/__init__.py b/stix2/__init__.py
index 76ca696..6e89531 100644
--- a/stix2/__init__.py
+++ b/stix2/__init__.py
@@ -3,10 +3,9 @@
 # flake8: noqa
 
 from . import exceptions
-from .common import (TLP_AMBER, TLP_GREEN, TLP_RED, TLP_WHITE,
-                     CustomMarking, ExternalReference, GranularMarking,
-                     KillChainPhase, MarkingDefinition, StatementMarking,
-                     TLPMarking)
+from .common import (TLP_AMBER, TLP_GREEN, TLP_RED, TLP_WHITE, CustomMarking,
+                     ExternalReference, GranularMarking, KillChainPhase,
+                     MarkingDefinition, StatementMarking, TLPMarking)
 from .core import Bundle, _register_type, parse
 from .environment import ObjectFactory
 from .observables import (URL, AlternateDataStream, ArchiveExt, Artifact,
diff --git a/stix2/properties.py b/stix2/properties.py
index a04294e..6406ad4 100644
--- a/stix2/properties.py
+++ b/stix2/properties.py
@@ -6,7 +6,6 @@ import re
 import uuid
 
 from six import string_types, text_type
-
 from stix2patterns.validator import run_validator
 
 from .base import _STIXBase
diff --git a/stix2/sources/__init__.py b/stix2/sources/__init__.py
index 87ff913..424fc3a 100644
--- a/stix2/sources/__init__.py
+++ b/stix2/sources/__init__.py
@@ -17,7 +17,6 @@ Notes:
 """
 
 import collections
-import copy
 import uuid
 
 from six import iteritems
diff --git a/stix2/sources/memory.py b/stix2/sources/memory.py
index 6460ce3..28d929d 100644
--- a/stix2/sources/memory.py
+++ b/stix2/sources/memory.py
@@ -21,9 +21,10 @@ Notes:
 import json
 import os
 
+from stix2validator import validate_string
+
 from stix2 import Bundle
 from stix2.sources import DataSink, DataSource, DataStore, Filter
-from stix2validator import validate_string
 
 
 class MemoryStore(DataStore):
diff --git a/stix2/test/test_custom.py b/stix2/test/test_custom.py
index 2b08883..0ca6fbd 100644
--- a/stix2/test/test_custom.py
+++ b/stix2/test/test_custom.py
@@ -135,32 +135,12 @@ def test_custom_no_properties_raises_exception():
         class NewObject1(object):
             pass
 
-        NewObject1()
-
-        @stix2.sdo.CustomObject('x-new-object-type', ("a", 0))
-        class NewObject2(object):
-            pass
-
-        NewObject2()
-
-        @stix2.observables.CustomObservable('x-new-object-type')
-        class NewObject3(object):
-            pass
-
-        NewObject3()
+    with pytest.raises(ValueError):
 
         @stix2.observables.CustomObservable('x-new-object-type', (("prop", stix2.properties.BooleanProperty())))
         class NewObject4(object):
             pass
 
-        NewObject4()
-
-        @stix2.common.CustomMarking('x-new-marking-type')
-        class NewObject5(object):
-            pass
-
-        NewObject5()
-
 
 def test_parse_custom_observable_object():
     nt_string = """{
diff --git a/stix2/test/test_data_sources.py b/stix2/test/test_data_sources.py
index df70878..10e4cc7 100644
--- a/stix2/test/test_data_sources.py
+++ b/stix2/test/test_data_sources.py
@@ -1,7 +1,8 @@
 import pytest
 from taxii2client import Collection
 
-from stix2.sources import CompositeDataSource, DataSink, DataSource, DataStore, Filter, make_id, taxii
+from stix2.sources import (CompositeDataSource, DataSink, DataSource,
+                           DataStore, Filter, make_id, taxii)
 from stix2.sources.memory import MemorySource
 
 COLLECTION_URL = 'https://example.com/api1/collections/91a7b528-80eb-42ed-a74d-c6fbd5a26116/'
@@ -24,8 +25,14 @@ def test_ds_smoke():
 
     with pytest.raises(NotImplementedError):
         ds3.add(None)
+
+    with pytest.raises(NotImplementedError):
         ds3.all_versions("malware--fdd60b30-b67c-11e3-b0b9-f01faf20d111")
+
+    with pytest.raises(NotImplementedError):
         ds3.get("malware--fdd60b30-b67c-11e3-b0b9-f01faf20d111")
+
+    with pytest.raises(NotImplementedError):
         ds3.query([Filter("id", "=", "malware--fdd60b30-b67c-11e3-b0b9-f01faf20d111")])
 
 
@@ -170,6 +177,7 @@ def test_apply_common_filters():
     resp = ds.apply_common_filters(stix_objs, [filters[2]])
     assert resp[0]['id'] == stix_objs[0]['id']
 
+
 STIX_OBJS1 = [
     {
         "created": "2017-01-27T13:49:53.935Z",
diff --git a/stix2/test/test_markings.py b/stix2/test/test_markings.py
index 4e39c54..c9d9273 100644
--- a/stix2/test/test_markings.py
+++ b/stix2/test/test_markings.py
@@ -187,8 +187,7 @@ def test_parse_marking_definition(data):
 ])
 class NewMarking(object):
     def __init__(self, property2=None, **kwargs):
-        if property2 and property2 < 10:
-            raise ValueError("'property2' is too small.")
+        return
 
 
 def test_registered_custom_marking():
@@ -217,8 +216,7 @@ def test_not_registered_marking_raises_exception():
         ])
         class NewObject2(object):
             def __init__(self, property2=None, **kwargs):
-                if property2 and property2 < 10:
-                    raise ValueError("'property2' is too small.")
+                return
 
         no = NewObject2(property1='something', property2=55)
 
@@ -230,4 +228,11 @@ def test_not_registered_marking_raises_exception():
         )
 
 
+def test_bad_marking_construction():
+    with pytest.raises(ValueError):
+        @stix2.sdo.CustomObject('x-new-marking-type2', ("a", "b"))
+        class NewObject3(object):
+            pass
+
+
 # TODO: Add other examples