diff --git a/.travis.yml b/.travis.yml
index f7d01c7cbd4ac..4737365c7bd07 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -42,24 +42,19 @@ matrix:
     - env: DISTRIB="conda" PYTHON_VERSION="3.6.2" INSTALL_MKL="true"
            NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" PANDAS_VERSION="0.20.3"
            CYTHON_VERSION="0.26.1" COVERAGE=true
-      if: type != cron
-    # This environment use pytest to run the tests. It uses the newest
-    # supported Anaconda release (5.0.0). It also runs tests requiring Pandas.
-    - env: USE_PYTEST="true" DISTRIB="conda" PYTHON_VERSION="3.6.2"
-           INSTALL_MKL="true" NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1"
-           PANDAS_VERSION="0.20.3" CYTHON_VERSION="0.26.1"
-           TEST_DOCSTRINGS="true"
+           CHECK_PYTEST_SOFT_DEPENDENCY="true"
       if: type != cron
     # flake8 linting on diff wrt common ancestor with upstream/master
     - env: RUN_FLAKE8="true" SKIP_TESTS="true"
            DISTRIB="conda" PYTHON_VERSION="3.5" INSTALL_MKL="true"
-           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1" CYTHON_VERSION="0.26.1"
+           NUMPY_VERSION="1.13.1" SCIPY_VERSION="0.19.1"
+           CYTHON_VERSION="0.26.1"
       if: type != cron
     # This environment tests scikit-learn against numpy and scipy master
     # installed from their CI wheels in a virtualenv with the Python
     # interpreter provided by travis.
     -  python: 3.6
-       env: USE_PYTEST="true" DISTRIB="scipy-dev-wheels"
+       env: DISTRIB="scipy-dev-wheels"
        if: type = cron
 
 install: source build_tools/travis/install.sh
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 6f643fc46c4e5..c217e73354f81 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -139,8 +139,8 @@ tools:
 -  Code with good unittest **coverage** (at least 80%), check with:
 
   ```bash
-  $ pip install nose coverage
-  $ nosetests --with-coverage path/to/tests_for_package
+  $ pip install pytest pytest-cov
+  $ pytest --cov sklearn path/to/tests_for_package
   ```
 
 -  No pyflakes warnings, check with:
diff --git a/Makefile b/Makefile
index aa6203f3cdbe7..6725a7441f75a 100644
--- a/Makefile
+++ b/Makefile
@@ -4,17 +4,12 @@
 
 PYTHON ?= python
 CYTHON ?= cython
-NOSETESTS ?= nosetests
+PYTEST ?= pytest
 CTAGS ?= ctags
 
 # skip doctests on 32bit python
 BITS := $(shell python -c 'import struct; print(8 * struct.calcsize("P"))')
 
-ifeq ($(BITS),32)
-  NOSETESTS:=$(NOSETESTS) -c setup32.cfg
-endif
-
-
 all: clean inplace test
 
 clean-ctags:
@@ -29,19 +24,17 @@ inplace:
 	$(PYTHON) setup.py build_ext -i
 
 test-code: in
-	$(NOSETESTS) -s -v sklearn
+	$(PYTEST) --showlocals -v sklearn
 test-sphinxext:
-	$(NOSETESTS) -s -v doc/sphinxext/
+	$(PYTEST) --showlocals -v doc/sphinxext/
 test-doc:
 ifeq ($(BITS),64)
-	$(NOSETESTS) -s -v doc/*.rst doc/modules/ doc/datasets/ \
-	doc/developers doc/tutorial/basic doc/tutorial/statistical_inference \
-	doc/tutorial/text_analytics
+	$(PYTEST) $(shell find doc -name '*.rst' | sort)
 endif
 
 test-coverage:
 	rm -rf coverage .coverage
-	$(NOSETESTS) -s -v --with-coverage sklearn
+	$(PYTEST) sklearn --show-locals -v --with-cov sklearn
 
 test: test-code test-sphinxext test-doc
 
diff --git a/README.rst b/README.rst
index 64c8875be6c07..a1ec4c06f5358 100644
--- a/README.rst
+++ b/README.rst
@@ -110,15 +110,9 @@ Testing
 ~~~~~~~
 
 After installation, you can launch the test suite from outside the
-source directory (you will need to have the ``nose`` package installed)::
+source directory (you will need to have the ``pytest`` package installed)::
 
-    nosetests -v sklearn
-
-Under Windows, it is recommended to use the following command (adjust the path
-to the ``python.exe`` program) as using the ``nosetests.exe`` program can badly
-interact with tests that use ``multiprocessing``::
-
-    C:\Python34\python.exe -c "import nose; nose.main()" -v sklearn
+    pytest sklearn
 
 See the web page http://scikit-learn.org/stable/developers/advanced_installation.html#testing
 for more information.
diff --git a/appveyor.yml b/appveyor.yml
index 768089e880e25..dac1417cafd4c 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -78,12 +78,11 @@ build: false
 test_script:
   # Change to a non-source folder to make sure we run the tests on the
   # installed library.
-  - "mkdir empty_folder"
-  - "cd empty_folder"
-  - "python -c \"import nose; nose.main()\" --with-timer --timer-top-n 20 -s sklearn"
-
+  - mkdir "../empty_folder"
+  - cd "../empty_folder"
+  - pytest --showlocals --durations=20 --pyargs sklearn
   # Move back to the project folder
-  - "cd .."
+  - cd "../scikit-learn"
 
 artifacts:
   # Archive the generated wheel package in the ci.appveyor.com build report.
diff --git a/build_tools/appveyor/requirements.txt b/build_tools/appveyor/requirements.txt
index 0b9c63f72789f..26fa790392b31 100644
--- a/build_tools/appveyor/requirements.txt
+++ b/build_tools/appveyor/requirements.txt
@@ -10,7 +10,6 @@
 numpy==1.9.3
 scipy==0.16.0
 cython
-nose
-nose-timer
+pytest
 wheel
 wheelhouse_uploader
diff --git a/build_tools/circle/build_doc.sh b/build_tools/circle/build_doc.sh
index 0be1dda05f049..ec17e52e80e05 100755
--- a/build_tools/circle/build_doc.sh
+++ b/build_tools/circle/build_doc.sh
@@ -107,7 +107,7 @@ conda update --yes --quiet conda
 # Configure the conda environment and put it in the path using the
 # provided versions
 conda create -n $CONDA_ENV_NAME --yes --quiet python numpy scipy \
-  cython nose coverage matplotlib sphinx=1.6.2 pillow
+  cython pytest coverage matplotlib sphinx=1.6.2 pillow
 source activate testenv
 pip install sphinx-gallery
 # Use numpydoc master (for now)
diff --git a/build_tools/travis/after_success.sh b/build_tools/travis/after_success.sh
index aead28cb2865d..f15aaabd07097 100755
--- a/build_tools/travis/after_success.sh
+++ b/build_tools/travis/after_success.sh
@@ -8,7 +8,7 @@ set -e
 
 if [[ "$COVERAGE" == "true" ]]; then
     # Need to run codecov from a git checkout, so we copy .coverage
-    # from TEST_DIR where nosetests has been run
+    # from TEST_DIR where pytest has been run
     cp $TEST_DIR/.coverage $TRAVIS_BUILD_DIR
     cd $TRAVIS_BUILD_DIR
     # Ignore codecov failures as the codecov server is not
diff --git a/build_tools/travis/install.sh b/build_tools/travis/install.sh
index ad402bb35ae02..f1f574ac822af 100755
--- a/build_tools/travis/install.sh
+++ b/build_tools/travis/install.sh
@@ -39,31 +39,20 @@ if [[ "$DISTRIB" == "conda" ]]; then
 
     # Configure the conda environment and put it in the path using the
     # provided versions
-    if [[ "$USE_PYTEST" == "true" ]]; then
-        TEST_RUNNER_PACKAGE=pytest
-    else
-        TEST_RUNNER_PACKAGE=nose
-    fi
-
     if [[ "$INSTALL_MKL" == "true" ]]; then
         conda create -n testenv --yes python=$PYTHON_VERSION pip \
-            $TEST_RUNNER_PACKAGE numpy=$NUMPY_VERSION scipy=$SCIPY_VERSION \
+            pytest pytest-cov numpy=$NUMPY_VERSION scipy=$SCIPY_VERSION \
             mkl cython=$CYTHON_VERSION \
             ${PANDAS_VERSION+pandas=$PANDAS_VERSION}
             
     else
         conda create -n testenv --yes python=$PYTHON_VERSION pip \
-            $TEST_RUNNER_PACKAGE numpy=$NUMPY_VERSION scipy=$SCIPY_VERSION \
+            pytest pytest-cov numpy=$NUMPY_VERSION scipy=$SCIPY_VERSION \
             nomkl cython=$CYTHON_VERSION \
             ${PANDAS_VERSION+pandas=$PANDAS_VERSION}
     fi
     source activate testenv
 
-    if [[ $USE_PYTEST != "true" ]]; then
-        # Install nose-timer via pip
-        pip install nose-timer
-    fi
-
 elif [[ "$DISTRIB" == "ubuntu" ]]; then
     # At the time of writing numpy 1.9.1 is included in the travis
     # virtualenv but we want to use the numpy installed through apt-get
@@ -73,7 +62,7 @@ elif [[ "$DISTRIB" == "ubuntu" ]]; then
     # and scipy
     virtualenv --system-site-packages testvenv
     source testvenv/bin/activate
-    pip install nose nose-timer cython==$CYTHON_VERSION
+    pip install pytest pytest-cov cython==$CYTHON_VERSION
 
 elif [[ "$DISTRIB" == "scipy-dev-wheels" ]]; then
     # Set up our own virtualenv environment to avoid travis' numpy.
@@ -86,12 +75,7 @@ elif [[ "$DISTRIB" == "scipy-dev-wheels" ]]; then
     echo "Installing numpy and scipy master wheels"
     dev_url=https://7933911d6844c6c53a7d-47bd50c35cd79bd838daf386af554a83.ssl.cf2.rackcdn.com
     pip install --pre --upgrade --timeout=60 -f $dev_url numpy scipy pandas cython
-    if [[ $USE_PYTEST == "true" ]]; then
-        pip install pytest
-    else
-        # Install nose-timer via pip
-        pip install nose nose-timer
-    fi
+    pip install pytest pytest-cov
 fi
 
 if [[ "$COVERAGE" == "true" ]]; then
@@ -102,8 +86,8 @@ if [[ "$TEST_DOCSTRINGS" == "true" ]]; then
     pip install sphinx numpydoc  # numpydoc requires sphinx
 fi
 
-if [[ "$SKIP_TESTS" == "true" ]]; then
-    echo "No need to build scikit-learn when not running the tests"
+if [[ "$SKIP_TESTS" == "true" && "$CHECK_PYTEST_SOFT_DEPENDENCY" != "true" ]]; then
+    echo "No need to build scikit-learn"
 else
     # Build scikit-learn in the install.sh script to collapse the verbose
     # build output in the travis output when it succeeds.
diff --git a/build_tools/travis/test_script.sh b/build_tools/travis/test_script.sh
index 0ed6f5e3b87a0..c4309c7cb3683 100755
--- a/build_tools/travis/test_script.sh
+++ b/build_tools/travis/test_script.sh
@@ -21,15 +21,12 @@ except ImportError:
 python -c "import multiprocessing as mp; print('%d CPUs' % mp.cpu_count())"
 
 run_tests() {
-    if [[ "$USE_PYTEST" == "true" ]]; then
-        TEST_CMD="pytest --showlocals --durations=20 --pyargs"
-    else
-        TEST_CMD="nosetests --with-timer --timer-top-n 20"
-    fi
+    TEST_CMD="pytest --showlocals --durations=20 --pyargs"
+
     # Get into a temp directory to run test from the installed scikit-learn and
     # check if we do not leave artifacts
     mkdir -p $TEST_DIR
-    # We need the setup.cfg for the nose settings
+    # We need the setup.cfg for the pytest settings
     cp setup.cfg $TEST_DIR
     cd $TEST_DIR
 
@@ -39,23 +36,18 @@ run_tests() {
     export SKLEARN_SKIP_NETWORK_TESTS=1
 
     if [[ "$COVERAGE" == "true" ]]; then
-        TEST_CMD="$TEST_CMD --with-coverage"
+        TEST_CMD="$TEST_CMD --cov sklearn"
     fi
     $TEST_CMD sklearn
 
     # Going back to git checkout folder needed to test documentation
     cd $OLDPWD
 
-    if [[ "$USE_PYTEST" == "true" ]]; then
-        # Do not run doctests in scipy-dev-wheels build for now
-        # (broken by numpy 1.14.dev array repr/str formatting
-        # change even with np.set_printoptions(sign='legacy')).
-        # See https://github.com/numpy/numpy/issues/9804 for more details
-        if [[ "$DISTRIB" != "scipy-dev-wheels" ]]; then
-            pytest $(find doc -name '*.rst' | sort)
-        fi
-    else
-        # Makefile is using nose
+    # Do not run doctests in scipy-dev-wheels build for now
+    # (broken by numpy 1.14.dev array repr/str formatting
+    # change even with np.set_printoptions(sign='legacy')).
+    # See https://github.com/numpy/numpy/issues/9804 for more details
+    if [[ "$DISTRIB" != "scipy-dev-wheels" ]]; then
         make test-doc
     fi
 }
@@ -67,3 +59,18 @@ fi
 if [[ "$SKIP_TESTS" != "true" ]]; then
     run_tests
 fi
+
+if [[ "$CHECK_PYTEST_SOFT_DEPENDENCY" == "true" ]]; then
+    conda remove -y py pytest || pip uninstall -y py pytest
+    if [[ "$COVERAGE" == "true" ]]; then
+        # Need to append the coverage to the existing .coverage generated by
+        # running the tests
+        CMD="coverage run --append"
+    else
+        CMD="python"
+    fi
+    # .coverage from running the tests is in TEST_DIR
+    cd $TEST_DIR
+    $CMD -m sklearn.utils.tests.test_estimator_checks
+    cd $OLDPWD
+fi
diff --git a/doc/developers/advanced_installation.rst b/doc/developers/advanced_installation.rst
index 4a9e82ff17f5d..1566fa5302ba7 100644
--- a/doc/developers/advanced_installation.rst
+++ b/doc/developers/advanced_installation.rst
@@ -376,24 +376,17 @@ Testing
 Testing scikit-learn once installed
 -----------------------------------
 
-Testing requires having the `nose
-<https://nose.readthedocs.io/en/latest/>`_ library. After
+Testing requires having the `pytest
+<https://docs.pytest.org>`_ library. After
 installation, the package can be tested by executing *from outside* the
 source directory::
 
-    $ nosetests -v sklearn
-
-Under Windows, it is recommended to use the following command (adjust the path
-to the ``python.exe`` program) as using the ``nosetests.exe`` program can badly
-interact with tests that use ``multiprocessing``::
-
-    C:\Python34\python.exe -c "import nose; nose.main()" -v sklearn
+    $ pytest sklearn
 
 This should give you a lot of output (and some warnings) but
 eventually should finish with a message similar to::
 
-    Ran 3246 tests in 260.618s
-    OK (SKIP=20)
+    =========== 8304 passed, 26 skipped, 4659 warnings in 557.76 seconds ===========
 
 Otherwise, please consider posting an issue into the `bug tracker
 <https://github.com/scikit-learn/scikit-learn/issues>`_ or to the
@@ -411,9 +404,9 @@ source directory::
 
     python setup.py build_ext --inplace
 
-Test can now be run using nosetests::
+Test can now be run using pytest::
 
-    nosetests -v sklearn/
+    pytest sklearn
 
 This is automated by the commands::
 
diff --git a/doc/developers/contributing.rst b/doc/developers/contributing.rst
index 72e68bc458750..292453d7a8f4c 100644
--- a/doc/developers/contributing.rst
+++ b/doc/developers/contributing.rst
@@ -280,8 +280,8 @@ You can also check for common programming errors with the following tools:
     * Code with a good unittest coverage (at least 90%, better 100%), check
       with::
 
-        $ pip install nose coverage
-        $ nosetests --with-coverage path/to/tests_for_package
+        $ pip install pytest pytest-cov
+        $ pytest --cov sklearn path/to/tests_for_package
 
       see also :ref:`testing_coverage`
 
@@ -519,13 +519,13 @@ Testing and improving test coverage
 
 High-quality `unit testing <https://en.wikipedia.org/wiki/Unit_testing>`_
 is a corner-stone of the scikit-learn development process. For this
-purpose, we use the `nose <http://nose.readthedocs.io/en/latest/>`_
+purpose, we use the `pytest <https://docs.pytest.org>`_
 package. The tests are functions appropriately named, located in `tests`
 subdirectories, that check the validity of the algorithms and the
 different options of the code.
 
 The full scikit-learn tests can be run using 'make' in the root folder.
-Alternatively, running 'nosetests' in a folder will run all the tests of
+Alternatively, running 'pytest' in a folder will run all the tests of
 the corresponding subpackages.
 
 We expect code coverage of new features to be at least around 90%.
@@ -533,7 +533,7 @@ We expect code coverage of new features to be at least around 90%.
 .. note:: **Workflow to improve test coverage**
 
    To test code coverage, you need to install the `coverage
-   <https://pypi.python.org/pypi/coverage>`_ package in addition to nose.
+   <https://pypi.python.org/pypi/coverage>`_ package in addition to pytest.
 
    1. Run 'make test-coverage'. The output lists for each file the line
       numbers that are not tested.
diff --git a/setup.cfg b/setup.cfg
index 02b3015e87f2e..f96e9cf9f85ab 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,30 +1,9 @@
 [aliases]
-# python2.7 has upgraded unittest and it is no longer compatible with some
-# of our tests, so we run all through nose
-test = nosetests
-
-[nosetests]
-# nosetests skips test files with the executable bit by default
-# which can silently hide failing tests.
-# There are no executable scripts within the scikit-learn project
-# so let's turn the --exe flag on to avoid skipping tests by
-# mistake.
-exe = 1
-cover-html = 1
-cover-html-dir = coverage
-cover-package = sklearn
-
-detailed-errors = 1
-with-doctest = 1
-doctest-tests = 1
-doctest-extension = rst
-doctest-fixtures = _fixture
-ignore-files=^setup\.py$
-#doctest-options = +ELLIPSIS,+NORMALIZE_WHITESPACE
+test = pytest
 
 [tool:pytest]
-# disable-pytest-warnings should be removed once we drop nose and we
-# rewrite tests using yield with parametrize
+# disable-pytest-warnings should be removed once we rewrite tests
+# using yield with parametrize
 addopts =
     --doctest-modules
     --disable-pytest-warnings
diff --git a/setup32.cfg b/setup32.cfg
deleted file mode 100644
index 7294cb813fc8d..0000000000000
--- a/setup32.cfg
+++ /dev/null
@@ -1,22 +0,0 @@
-# This config file is here to skip doctests on 32bit linux when running make or make test
-# For newer versions of nose, we can simply use "NOSE_IGNORE_CONFIG_FILES", which
-# we should do in the future.
-
-[aliases]
-# python2.7 has upgraded unittest and it is no longer compatible with some
-# of our tests, so we run all through nose
-test = nosetests
-
-[nosetests]
-# nosetests skips test files with the executable bit by default
-# which can silently hide failing tests.
-# There are no executable scripts within the scikit-learn project
-# so let's turn the --exe flag on to avoid skipping tests by
-# mistake.
-exe = 1
-cover-html = 1
-cover-html-dir = coverage
-cover-package = sklearn
-
-detailed-errors = 1
-with-doctest = 0
diff --git a/sklearn/cross_validation.py b/sklearn/cross_validation.py
index 7646459da3936..3198c39139210 100644
--- a/sklearn/cross_validation.py
+++ b/sklearn/cross_validation.py
@@ -1953,9 +1953,6 @@ def permutation_test_score(estimator, X, y, cv=None,
     return score, permutation_scores, pvalue
 
 
-permutation_test_score.__test__ = False  # to avoid a pb with nosetests
-
-
 def train_test_split(*arrays, **options):
     """Split arrays or matrices into random train and test subsets
 
@@ -2070,6 +2067,3 @@ def train_test_split(*arrays, **options):
     train, test = next(iter(cv))
     return list(chain.from_iterable((safe_indexing(a, train),
                                      safe_indexing(a, test)) for a in arrays))
-
-
-train_test_split.__test__ = False  # to avoid a pb with nosetests
diff --git a/sklearn/externals/copy_joblib.sh b/sklearn/externals/copy_joblib.sh
index f6db76c9df5b3..398b567b81743 100755
--- a/sklearn/externals/copy_joblib.sh
+++ b/sklearn/externals/copy_joblib.sh
@@ -24,7 +24,3 @@ find joblib -name "*.bak" | xargs rm
 # Remove the tests folders to speed-up test time for scikit-learn.
 # joblib is already tested on its own CI infrastructure upstream.
 rm -r joblib/test
-
-# Remove joblib/testing.py which is only used in tests and has a
-# pytest dependency (needed until we drop nose)
-rm joblib/testing.py
diff --git a/sklearn/externals/test_externals_setup.py b/sklearn/externals/test_externals_setup.py
deleted file mode 100644
index d3198050a33b1..0000000000000
--- a/sklearn/externals/test_externals_setup.py
+++ /dev/null
@@ -1,10 +0,0 @@
-"""
-Fixtures to get the external bundled dependencies tested.
-
-This module gets loaded by test discovery scanners (such as nose) in
-their collection scan.
-"""
-
-import sys
-import os
-sys.path.append(os.path.abspath(os.path.dirname(__file__)))
diff --git a/sklearn/model_selection/_split.py b/sklearn/model_selection/_split.py
index 24d9423b22278..b12f309de33cd 100644
--- a/sklearn/model_selection/_split.py
+++ b/sklearn/model_selection/_split.py
@@ -2059,9 +2059,6 @@ def train_test_split(*arrays, **options):
                                      safe_indexing(a, test)) for a in arrays))
 
 
-train_test_split.__test__ = False  # to avoid a pb with nosetests
-
-
 def _build_repr(self):
     # XXX This is copied from BaseEstimator's get_params
     cls = self.__class__
diff --git a/sklearn/model_selection/_validation.py b/sklearn/model_selection/_validation.py
index fdf6fa6912544..24362620c809f 100644
--- a/sklearn/model_selection/_validation.py
+++ b/sklearn/model_selection/_validation.py
@@ -948,9 +948,6 @@ def permutation_test_score(estimator, X, y, groups=None, cv=None,
     return score, permutation_scores, pvalue
 
 
-permutation_test_score.__test__ = False  # to avoid a pb with nosetests
-
-
 def _permutation_test_score(estimator, X, y, groups, cv, scorer):
     """Auxiliary function for permutation_test_score"""
     avg_score = []
diff --git a/sklearn/tree/tests/test_tree.py b/sklearn/tree/tests/test_tree.py
index 71ee8fa2bcb61..c209c93ae3c99 100644
--- a/sklearn/tree/tests/test_tree.py
+++ b/sklearn/tree/tests/test_tree.py
@@ -1549,7 +1549,6 @@ def test_1d_input():
 
 
 def _check_min_weight_leaf_split_level(TreeEstimator, X, y, sample_weight):
-    # Private function to keep pretty printing in nose yielded tests
     est = TreeEstimator(random_state=0)
     est.fit(X, y, sample_weight=sample_weight)
     assert_equal(est.tree_.max_depth, 1)
diff --git a/sklearn/utils/tests/test_estimator_checks.py b/sklearn/utils/tests/test_estimator_checks.py
index 2323f8a634eb2..dff080187d24d 100644
--- a/sklearn/utils/tests/test_estimator_checks.py
+++ b/sklearn/utils/tests/test_estimator_checks.py
@@ -1,6 +1,10 @@
-import scipy.sparse as sp
-import numpy as np
+import unittest
 import sys
+
+import numpy as np
+
+import scipy.sparse as sp
+
 from sklearn.externals.six.moves import cStringIO as StringIO
 from sklearn.externals import joblib
 
@@ -248,7 +252,6 @@ def __init__(self):
            'should not be initialized in the constructor.+'
            "Attribute 'you_should_not_set_this_' was found.+"
            'in estimator estimator_name')
-
     assert_raises_regex(AssertionError, msg,
                         check_no_fit_attributes_set_in_init,
                         'estimator_name',
@@ -266,3 +269,22 @@ def test_check_estimator_pairwise():
     # test precomputed metric
     est = KNeighborsRegressor(metric='precomputed')
     check_estimator(est)
+
+
+def run_tests_without_pytest():
+    """Runs the tests in this file without using pytest.
+    """
+    main_module = sys.modules['__main__']
+    test_functions = [getattr(main_module, name) for name in dir(main_module)
+                      if name.startswith('test_')]
+    test_cases = [unittest.FunctionTestCase(fn) for fn in test_functions]
+    suite = unittest.TestSuite()
+    suite.addTests(test_cases)
+    runner = unittest.TextTestRunner()
+    runner.run(suite)
+
+
+if __name__ == '__main__':
+    # This module is run as a script to check that we have no dependency on
+    # pytest for estimator checks.
+    run_tests_without_pytest()