diff --git a/imblearn/combine/tests/test_smote_enn.py b/imblearn/combine/tests/test_smote_enn.py
index 7d41083df..67c7cca90 100644
--- a/imblearn/combine/tests/test_smote_enn.py
+++ b/imblearn/combine/tests/test_smote_enn.py
@@ -6,9 +6,10 @@
 from __future__ import print_function
 
 import numpy as np
-from sklearn.utils.testing import assert_allclose, assert_array_equal
 from pytest import raises
 
+from sklearn.utils.testing import assert_allclose, assert_array_equal
+
 from imblearn.combine import SMOTEENN
 from imblearn.under_sampling import EditedNearestNeighbours
 from imblearn.over_sampling import SMOTE
diff --git a/imblearn/combine/tests/test_smote_tomek.py b/imblearn/combine/tests/test_smote_tomek.py
index ff401a34a..3da2243dc 100644
--- a/imblearn/combine/tests/test_smote_tomek.py
+++ b/imblearn/combine/tests/test_smote_tomek.py
@@ -6,9 +6,10 @@
 from __future__ import print_function
 
 import numpy as np
-from sklearn.utils.testing import assert_allclose, assert_array_equal
 from pytest import raises
 
+from sklearn.utils.testing import assert_allclose, assert_array_equal
+
 from imblearn.combine import SMOTETomek
 from imblearn.over_sampling import SMOTE
 from imblearn.under_sampling import TomekLinks
diff --git a/imblearn/datasets/tests/test_imbalance.py b/imblearn/datasets/tests/test_imbalance.py
index fc5d885fa..b54700d20 100644
--- a/imblearn/datasets/tests/test_imbalance.py
+++ b/imblearn/datasets/tests/test_imbalance.py
@@ -10,11 +10,11 @@
 
 import numpy as np
 
-from sklearn.datasets import load_iris
-from imblearn.utils.testing import warns
-
 from pytest import raises
 
+from sklearn.datasets import load_iris
+
+from imblearn.utils.testing import warns
 from imblearn.datasets import make_imbalance
 
 data = load_iris()
diff --git a/imblearn/ensemble/tests/test_balance_cascade.py b/imblearn/ensemble/tests/test_balance_cascade.py
index 2271b67f2..a01e561d3 100644
--- a/imblearn/ensemble/tests/test_balance_cascade.py
+++ b/imblearn/ensemble/tests/test_balance_cascade.py
@@ -6,13 +6,14 @@
 from __future__ import print_function
 
 import numpy as np
-from sklearn.utils.testing import assert_array_equal
 
+from pytest import raises
+
+from sklearn.utils.testing import assert_array_equal
 from sklearn.ensemble import RandomForestClassifier
 
 from imblearn.ensemble import BalanceCascade
 
-from pytest import raises
 
 RND_SEED = 0
 X = np.array([[0.11622591, -0.0317206], [0.77481731, 0.60935141],
diff --git a/imblearn/metrics/tests/test_classification.py b/imblearn/metrics/tests/test_classification.py
index 1b21470c4..76ac30c48 100644
--- a/imblearn/metrics/tests/test_classification.py
+++ b/imblearn/metrics/tests/test_classification.py
@@ -10,6 +10,8 @@
 
 import numpy as np
 
+from pytest import approx, raises
+
 from sklearn import datasets
 from sklearn import svm
 
@@ -31,7 +33,6 @@
 from imblearn.metrics import make_index_balanced_accuracy
 from imblearn.metrics import classification_report_imbalanced
 
-from pytest import approx, raises
 from imblearn.utils.testing import warns
 
 
diff --git a/imblearn/over_sampling/tests/test_adasyn.py b/imblearn/over_sampling/tests/test_adasyn.py
index 168be903c..c550d567f 100644
--- a/imblearn/over_sampling/tests/test_adasyn.py
+++ b/imblearn/over_sampling/tests/test_adasyn.py
@@ -6,12 +6,13 @@
 from __future__ import print_function
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_allclose, assert_array_equal
 from sklearn.neighbors import NearestNeighbors
 
 from imblearn.over_sampling import ADASYN
 
-from pytest import raises
 
 RND_SEED = 0
 X = np.array([[0.11622591, -0.0317206], [0.77481731, 0.60935141],
diff --git a/imblearn/over_sampling/tests/test_smote.py b/imblearn/over_sampling/tests/test_smote.py
index a90a2ba71..449ce9307 100644
--- a/imblearn/over_sampling/tests/test_smote.py
+++ b/imblearn/over_sampling/tests/test_smote.py
@@ -6,13 +6,14 @@
 from __future__ import print_function
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_allclose, assert_array_equal
 from sklearn.neighbors import NearestNeighbors
 from sklearn.svm import SVC
 
 from imblearn.over_sampling import SMOTE
 
-from pytest import raises
 
 RND_SEED = 0
 X = np.array([[0.11622591, -0.0317206], [0.77481731, 0.60935141],
diff --git a/imblearn/tests/test_exceptions.py b/imblearn/tests/test_exceptions.py
index 1421f8925..91ca4576a 100644
--- a/imblearn/tests/test_exceptions.py
+++ b/imblearn/tests/test_exceptions.py
@@ -3,11 +3,10 @@
 #          Christos Aridas
 # License: MIT
 
+from pytest import raises
 
 from imblearn.exceptions import raise_isinstance_error
 
-from pytest import raises
-
 
 def test_raise_isinstance_error():
     var = 10.0
diff --git a/imblearn/tests/test_pipeline.py b/imblearn/tests/test_pipeline.py
index ad045de1d..046fee903 100644
--- a/imblearn/tests/test_pipeline.py
+++ b/imblearn/tests/test_pipeline.py
@@ -11,6 +11,8 @@
 import time
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_array_equal
 from sklearn.utils.testing import assert_array_almost_equal
 from sklearn.utils.testing import assert_allclose
@@ -30,7 +32,6 @@
 from imblearn.under_sampling import (RandomUnderSampler,
                                      EditedNearestNeighbours as ENN)
 
-from pytest import raises
 
 JUNK_FOOD_DOCS = (
     "the pizza pizza beer copyright",
diff --git a/imblearn/under_sampling/prototype_generation/tests/test_cluster_centroids.py b/imblearn/under_sampling/prototype_generation/tests/test_cluster_centroids.py
index 8c14466e0..160e0df69 100644
--- a/imblearn/under_sampling/prototype_generation/tests/test_cluster_centroids.py
+++ b/imblearn/under_sampling/prototype_generation/tests/test_cluster_centroids.py
@@ -4,9 +4,10 @@
 from collections import Counter
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_allclose
 from sklearn.utils.testing import assert_array_equal
-from pytest import raises
 
 from sklearn.cluster import KMeans
 
diff --git a/imblearn/under_sampling/prototype_selection/tests/test_allknn.py b/imblearn/under_sampling/prototype_selection/tests/test_allknn.py
index f2d96da27..59207dcaf 100644
--- a/imblearn/under_sampling/prototype_selection/tests/test_allknn.py
+++ b/imblearn/under_sampling/prototype_selection/tests/test_allknn.py
@@ -6,13 +6,14 @@
 from __future__ import print_function
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_allclose, assert_array_equal
 from sklearn.neighbors import NearestNeighbors
 from sklearn.datasets import make_classification
 
 from imblearn.under_sampling import AllKNN
 
-from pytest import raises
 
 RND_SEED = 0
 X = np.array([[-0.12840393, 0.66446571], [1.32319756, -0.13181616],
diff --git a/imblearn/under_sampling/prototype_selection/tests/test_edited_nearest_neighbours.py b/imblearn/under_sampling/prototype_selection/tests/test_edited_nearest_neighbours.py
index 9674f7ac3..c06895eab 100644
--- a/imblearn/under_sampling/prototype_selection/tests/test_edited_nearest_neighbours.py
+++ b/imblearn/under_sampling/prototype_selection/tests/test_edited_nearest_neighbours.py
@@ -6,9 +6,10 @@
 from __future__ import print_function
 
 import numpy as np
-from sklearn.utils.testing import assert_array_equal
 from pytest import raises
 
+from sklearn.utils.testing import assert_array_equal
+
 from sklearn.neighbors import NearestNeighbors
 
 from imblearn.under_sampling import EditedNearestNeighbours
diff --git a/imblearn/under_sampling/prototype_selection/tests/test_instance_hardness_threshold.py b/imblearn/under_sampling/prototype_selection/tests/test_instance_hardness_threshold.py
index b9d4a865f..021077a09 100644
--- a/imblearn/under_sampling/prototype_selection/tests/test_instance_hardness_threshold.py
+++ b/imblearn/under_sampling/prototype_selection/tests/test_instance_hardness_threshold.py
@@ -6,13 +6,13 @@
 from __future__ import print_function
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_array_equal
 from sklearn.ensemble import GradientBoostingClassifier
-from pytest import raises
 
 from imblearn.under_sampling import InstanceHardnessThreshold
 
-from pytest import raises
 
 RND_SEED = 0
 X = np.array([[-0.3879569, 0.6894251], [-0.09322739, 1.28177189],
diff --git a/imblearn/under_sampling/prototype_selection/tests/test_nearmiss.py b/imblearn/under_sampling/prototype_selection/tests/test_nearmiss.py
index 8891422fc..a50fca349 100644
--- a/imblearn/under_sampling/prototype_selection/tests/test_nearmiss.py
+++ b/imblearn/under_sampling/prototype_selection/tests/test_nearmiss.py
@@ -6,13 +6,15 @@
 from __future__ import print_function
 
 import numpy as np
+from pytest import raises
+
 from sklearn.utils.testing import assert_array_equal
-from imblearn.utils.testing import warns
 from sklearn.neighbors import NearestNeighbors
-from pytest import raises
 
 from imblearn.under_sampling import NearMiss
 
+from imblearn.utils.testing import warns
+
 RND_SEED = 0
 X = np.array([[1.17737838, -0.2002118],
               [0.4960075, 0.86130762],
diff --git a/imblearn/under_sampling/prototype_selection/tests/test_neighbourhood_cleaning_rule.py b/imblearn/under_sampling/prototype_selection/tests/test_neighbourhood_cleaning_rule.py
index dae89f0cd..fb21f43db 100644
--- a/imblearn/under_sampling/prototype_selection/tests/test_neighbourhood_cleaning_rule.py
+++ b/imblearn/under_sampling/prototype_selection/tests/test_neighbourhood_cleaning_rule.py
@@ -3,12 +3,11 @@
 #          Christos Aridas
 # License: MIT
 
-from __future__ import print_function
-
 import numpy as np
-from sklearn.utils.testing import assert_array_equal
 from pytest import raises
 
+from sklearn.utils.testing import assert_array_equal
+
 from sklearn.neighbors import NearestNeighbors
 
 from imblearn.under_sampling import NeighbourhoodCleaningRule
diff --git a/imblearn/under_sampling/prototype_selection/tests/test_one_sided_selection.py b/imblearn/under_sampling/prototype_selection/tests/test_one_sided_selection.py
index 639f5063f..e5faf886a 100644
--- a/imblearn/under_sampling/prototype_selection/tests/test_one_sided_selection.py
+++ b/imblearn/under_sampling/prototype_selection/tests/test_one_sided_selection.py
@@ -6,9 +6,10 @@
 from __future__ import print_function
 
 import numpy as np
-from sklearn.utils.testing import assert_array_equal
 from pytest import raises
 
+from sklearn.utils.testing import assert_array_equal
+
 from sklearn.neighbors import KNeighborsClassifier
 
 from imblearn.under_sampling import OneSidedSelection
diff --git a/imblearn/utils/estimator_checks.py b/imblearn/utils/estimator_checks.py
index 17ca8b405..45a5c0b4e 100644
--- a/imblearn/utils/estimator_checks.py
+++ b/imblearn/utils/estimator_checks.py
@@ -12,14 +12,13 @@
 from collections import Counter
 
 import numpy as np
+from pytest import raises
 
 from sklearn.datasets import make_classification
 from sklearn.utils.estimator_checks import _yield_all_checks \
     as sklearn_yield_all_checks, check_estimator \
     as sklearn_check_estimator, check_parameters_default_constructible
 from sklearn.exceptions import NotFittedError
-from pytest import raises
-from imblearn.utils.testing import warns
 
 from sklearn.utils.testing import set_random_state
 
@@ -28,6 +27,8 @@
 from imblearn.under_sampling.base import BaseCleaningSampler, BaseUnderSampler
 from imblearn.ensemble.base import BaseEnsembleSampler
 
+from imblearn.utils.testing import warns
+
 
 def _yield_sampler_checks(name, Estimator):
     yield check_target_type
diff --git a/imblearn/utils/testing.py b/imblearn/utils/testing.py
index 1701b2c76..6d5a980d4 100644
--- a/imblearn/utils/testing.py
+++ b/imblearn/utils/testing.py
@@ -6,17 +6,16 @@
 
 import inspect
 import pkgutil
+from contextlib import contextmanager
+from re import compile
 
 from operator import itemgetter
-
-import imblearn
-from imblearn.base import SamplerMixin
+from pytest import warns as _warns
 
 from sklearn.base import BaseEstimator
 
-from pytest import warns as _warns
-from contextlib import contextmanager
-from re import compile
+from imblearn.base import SamplerMixin
+import imblearn
 
 
 # meta-estimators need another estimator to be instantiated.
diff --git a/imblearn/utils/tests/test_estimator_checks.py b/imblearn/utils/tests/test_estimator_checks.py
index a30cda348..73a49a2da 100644
--- a/imblearn/utils/tests/test_estimator_checks.py
+++ b/imblearn/utils/tests/test_estimator_checks.py
@@ -1,7 +1,10 @@
 """Estimator tests - adapted from scikit-learn"""
+import sys
+
 import scipy.sparse as sp
 import numpy as np
-import sys
+from pytest import raises
+
 from sklearn.externals.six.moves import cStringIO as StringIO
 
 from sklearn.base import BaseEstimator, ClassifierMixin
@@ -9,8 +12,6 @@
 
 from imblearn.utils.estimator_checks import check_estimator
 
-from pytest import raises
-
 
 class CorrectNotFittedError(ValueError):
     """Exception class to raise if estimator is used before fitting.
diff --git a/imblearn/utils/tests/test_validation.py b/imblearn/utils/tests/test_validation.py
index 3436a4012..08b2f5145 100644
--- a/imblearn/utils/tests/test_validation.py
+++ b/imblearn/utils/tests/test_validation.py
@@ -5,13 +5,13 @@
 
 from collections import Counter
 
+from pytest import raises
 import numpy as np
 
 from sklearn.neighbors.base import KNeighborsMixin
 from sklearn.neighbors import NearestNeighbors
 
 from imblearn.utils.testing import warns
-from pytest import raises
 
 from imblearn.utils import check_neighbors_object
 from imblearn.utils import check_ratio