diff --git a/test/conftest.py b/test/conftest.py
index a9bead2..0195712 100644
--- a/test/conftest.py
+++ b/test/conftest.py
@@ -1,4 +1,3 @@
-from __future__ import print_function
 import contextlib
 import logging
 import os
@@ -142,7 +141,7 @@ def container_ip(container):
             return net_info["bridge"]["IPAddress"]
 
         # not default bridge network, fallback on first network defined
-        network_name = net_info.keys()[0]
+        network_name = list(net_info.keys())[0]
         return net_info[network_name]["IPAddress"]
 
 
@@ -155,7 +154,7 @@ def container_ipv6(container):
         return net_info["bridge"]["GlobalIPv6Address"]
 
     # not default bridge network, fallback on first network defined
-    network_name = net_info.keys()[0]
+    network_name = list(net_info.keys())[0]
     return net_info[network_name]["GlobalIPv6Address"]
 
 
@@ -188,7 +187,7 @@ def docker_container_dns_resolver(domain_name):
     log = logging.getLogger('DNS')
     log.debug("docker_container_dns_resolver(%r)" % domain_name)
 
-    match = re.search('(^|.+\.)(?P<container>[^.]+)\.container\.docker$', domain_name)
+    match = re.search(r'(^|.+\.)(?P<container>[^.]+)\.container\.docker$', domain_name)
     if not match:
         log.debug("%r does not match" % domain_name)
         return
@@ -253,9 +252,12 @@ def get_nginx_conf_from_container(container):
     return the nginx /etc/nginx/conf.d/default.conf file content from a container
     """
     import tarfile
-    from cStringIO import StringIO
-    strm, stat = container.get_archive('/etc/nginx/conf.d/default.conf')
-    with tarfile.open(fileobj=StringIO(strm.read())) as tf:
+    from io import BytesIO
+
+    strm_generator, stat = container.get_archive('/etc/nginx/conf.d/default.conf')
+    strm_fileobj = BytesIO(b"".join(strm_generator))
+
+    with tarfile.open(fileobj=strm_fileobj) as tf:
         conffile = tf.extractfile('default.conf')
         return conffile.read()
 
@@ -264,7 +266,7 @@ def docker_compose_up(compose_file='docker-compose.yml'):
     logging.info('docker-compose -f %s up -d' % compose_file)
     try:
         subprocess.check_output(shlex.split('docker-compose -f %s up -d' % compose_file), stderr=subprocess.STDOUT)
-    except subprocess.CalledProcessError, e:
+    except subprocess.CalledProcessError as e:
         pytest.fail("Error while runninng 'docker-compose -f %s up -d':\n%s" % (compose_file, e.output), pytrace=False)
 
 
@@ -272,7 +274,7 @@ def docker_compose_down(compose_file='docker-compose.yml'):
     logging.info('docker-compose -f %s down' % compose_file)
     try:
         subprocess.check_output(shlex.split('docker-compose -f %s down' % compose_file), stderr=subprocess.STDOUT)
-    except subprocess.CalledProcessError, e:
+    except subprocess.CalledProcessError as e:
         pytest.fail("Error while runninng 'docker-compose -f %s down':\n%s" % (compose_file, e.output), pytrace=False)
 
 
@@ -286,7 +288,7 @@ def wait_for_nginxproxy_to_be_ready():
         return
     container = containers[0]
     for line in container.logs(stream=True):
-        if "Watching docker events" in line:
+        if b"Watching docker events" in line:
             logging.debug("nginx-proxy ready")
             break
 
@@ -337,7 +339,7 @@ def connect_to_network(network):
             return
 
         # figure out our container networks
-        my_networks = my_container.attrs["NetworkSettings"]["Networks"].keys()
+        my_networks = list(my_container.attrs["NetworkSettings"]["Networks"].keys())
 
         # make sure our container is connected to the nginx-proxy's network
         if network not in my_networks:
@@ -360,7 +362,7 @@ def disconnect_from_network(network=None):
             return
 
         # figure out our container networks
-        my_networks_names = my_container.attrs["NetworkSettings"]["Networks"].keys()
+        my_networks_names = list(my_container.attrs["NetworkSettings"]["Networks"].keys())
 
         # disconnect our container from the given network
         if network.name in my_networks_names:
@@ -378,7 +380,7 @@ def connect_to_all_networks():
         return []
     else:
         # find the list of docker networks
-        networks = filter(lambda network: len(network.containers) > 0 and network.name != 'bridge', docker_client.networks.list())
+        networks = [network for network in docker_client.networks.list() if len(network.containers) > 0 and network.name != 'bridge']
         return [connect_to_network(network) for network in networks]
 
 
@@ -388,7 +390,7 @@ def connect_to_all_networks():
 # 
 ###############################################################################
 
-@pytest.yield_fixture(scope="module")
+@pytest.fixture(scope="module")
 def docker_compose(request):
     """
     pytest fixture providing containers described in a docker compose file. After the tests, remove the created containers
@@ -412,7 +414,7 @@ def docker_compose(request):
     restore_urllib_dns_resolver(original_dns_resolver)
 
 
-@pytest.yield_fixture()
+@pytest.fixture()
 def nginxproxy():
     """
     Provides the `nginxproxy` object that can be used in the same way the requests module is:
diff --git a/test/requirements/Dockerfile-nginx-proxy-tester b/test/requirements/Dockerfile-nginx-proxy-tester
index 27d0538..6c0f060 100644
--- a/test/requirements/Dockerfile-nginx-proxy-tester
+++ b/test/requirements/Dockerfile-nginx-proxy-tester
@@ -1,4 +1,4 @@
-FROM python:2.7-alpine
+FROM python:3.9-alpine
 
 # Note: we're using alpine because it has openssl 1.0.2, which we need for testing
 RUN apk add --update bash openssl curl && rm -rf /var/cache/apk/*
diff --git a/test/stress_tests/test_deleted_cert/test_restart_while_missing_cert.py b/test/stress_tests/test_deleted_cert/test_restart_while_missing_cert.py
index 2b74acd..0ec36c7 100644
--- a/test/stress_tests/test_deleted_cert/test_restart_while_missing_cert.py
+++ b/test/stress_tests/test_deleted_cert/test_restart_while_missing_cert.py
@@ -12,7 +12,7 @@ script_dir = os.path.dirname(__file__)
 pytestmark = pytest.mark.xfail()  # TODO delete this marker once those issues are fixed
 
 
-@pytest.yield_fixture(scope="module", autouse=True)
+@pytest.fixture(scope="module", autouse=True)
 def certs():
     """
     pytest fixture that provides cert and key files into the tmp_certs directory
@@ -43,7 +43,7 @@ def test_http_web_is_301(docker_compose, nginxproxy):
 def test_https_web_is_200(docker_compose, nginxproxy):
     r = nginxproxy.get("https://web.nginx-proxy/port")
     assert r.status_code == 200
-    assert 'answer from port 81\n' in r.text
+    assert "answer from port 81\n" in r.text
 
 
 @pytest.mark.incremental
diff --git a/test/test_custom/test_location-per-vhost.py b/test/test_custom/test_location-per-vhost.py
index b99996e..f67b501 100644
--- a/test/test_custom/test_location-per-vhost.py
+++ b/test/test_custom/test_location-per-vhost.py
@@ -19,4 +19,4 @@ def test_custom_conf_does_not_apply_to_web2(docker_compose, nginxproxy):
     assert "X-test" not in r.headers
 
 def test_custom_block_is_present_in_nginx_generated_conf(docker_compose, nginxproxy):
-    assert "include /etc/nginx/vhost.d/web1.nginx-proxy.local_location;" in nginxproxy.get_conf()
\ No newline at end of file
+    assert b"include /etc/nginx/vhost.d/web1.nginx-proxy.local_location;" in nginxproxy.get_conf()
\ No newline at end of file
diff --git a/test/test_dockergen/test_dockergen_v2.py b/test/test_dockergen/test_dockergen_v2.py
index af02649..a3f2484 100644
--- a/test/test_dockergen/test_dockergen_v2.py
+++ b/test/test_dockergen/test_dockergen_v2.py
@@ -4,7 +4,7 @@ import logging
 import pytest
 
 
-@pytest.yield_fixture(scope="module")
+@pytest.fixture(scope="module")
 def nginx_tmpl():
     """
     pytest fixture which extracts the the nginx config template from
@@ -13,14 +13,18 @@ def nginx_tmpl():
     script_dir = os.path.dirname(__file__)
     logging.info("extracting nginx.tmpl from nginxproxy/nginx-proxy:test")
     docker_client = docker.from_env()
-    print(docker_client.containers.run(
-        image='nginxproxy/nginx-proxy:test',
-        remove=True,
-        volumes=['{current_dir}:{current_dir}'.format(current_dir=script_dir)],
-        entrypoint='sh',
-        command='-xc "cp /app/nginx.tmpl {current_dir} && chmod 777 {current_dir}/nginx.tmpl"'.format(
-            current_dir=script_dir),
-        stderr=True))
+    print(
+        docker_client.containers.run(
+            image="nginxproxy/nginx-proxy:test",
+            remove=True,
+            volumes=["{current_dir}:{current_dir}".format(current_dir=script_dir)],
+            entrypoint="sh",
+            command='-xc "cp /app/nginx.tmpl {current_dir} && chmod 777 {current_dir}/nginx.tmpl"'.format(
+                current_dir=script_dir
+            ),
+            stderr=True,
+        )
+    )
     yield
     logging.info("removing nginx.tmpl")
     os.remove(os.path.join(script_dir, "nginx.tmpl"))
diff --git a/test/test_dockergen/test_dockergen_v3.py b/test/test_dockergen/test_dockergen_v3.py
index 453889a..1beffeb 100644
--- a/test/test_dockergen/test_dockergen_v3.py
+++ b/test/test_dockergen/test_dockergen_v3.py
@@ -18,16 +18,18 @@ def versiontuple(v):
     >>> versiontuple("17.03.0-ce") < (1, 13)
     False
     """
-    return tuple(map(int, (v.split('-')[0].split("."))))
+    return tuple(map(int, (v.split("-")[0].split("."))))
 
 
-raw_version = docker.from_env().version()['Version']
+raw_version = docker.from_env().version()["Version"]
 pytestmark = pytest.mark.skipif(
     versiontuple(raw_version) < (1, 13),
-    reason="Docker compose syntax v3 requires docker engine v1.13 or later (got %s)" % raw_version)
+    reason="Docker compose syntax v3 requires docker engine v1.13 or later (got %s)"
+    % raw_version,
+)
 
 
-@pytest.yield_fixture(scope="module")
+@pytest.fixture(scope="module")
 def nginx_tmpl():
     """
     pytest fixture which extracts the the nginx config template from
@@ -36,14 +38,18 @@ def nginx_tmpl():
     script_dir = os.path.dirname(__file__)
     logging.info("extracting nginx.tmpl from nginxproxy/nginx-proxy:test")
     docker_client = docker.from_env()
-    print(docker_client.containers.run(
-        image='nginxproxy/nginx-proxy:test',
-        remove=True,
-        volumes=['{current_dir}:{current_dir}'.format(current_dir=script_dir)],
-        entrypoint='sh',
-        command='-xc "cp /app/nginx.tmpl {current_dir} && chmod 777 {current_dir}/nginx.tmpl"'.format(
-            current_dir=script_dir),
-        stderr=True))
+    print(
+        docker_client.containers.run(
+            image="nginxproxy/nginx-proxy:test",
+            remove=True,
+            volumes=["{current_dir}:{current_dir}".format(current_dir=script_dir)],
+            entrypoint="sh",
+            command='-xc "cp /app/nginx.tmpl {current_dir} && chmod 777 {current_dir}/nginx.tmpl"'.format(
+                current_dir=script_dir
+            ),
+            stderr=True,
+        )
+    )
     yield
     logging.info("removing nginx.tmpl")
     os.remove(os.path.join(script_dir, "nginx.tmpl"))
@@ -61,6 +67,6 @@ def test_forwards_to_whoami(nginx_tmpl, docker_compose, nginxproxy):
     assert r.text == "I'm %s\n" % whoami_container.id[:12]
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     import doctest
     doctest.testmod()
diff --git a/test/test_events.py b/test/test_events.py
index fa97f84..201917f 100644
--- a/test/test_events.py
+++ b/test/test_events.py
@@ -7,7 +7,7 @@ import pytest
 from docker.errors import NotFound
 
 
-@pytest.yield_fixture()
+@pytest.fixture()
 def web1(docker_compose):
     """
     pytest fixture creating a web container with `VIRTUAL_HOST=web1.nginx-proxy` listening on port 81.
diff --git a/test/test_ssl/test_dhparam.py b/test/test_ssl/test_dhparam.py
index 40339a1..8899c6a 100644
--- a/test/test_ssl/test_dhparam.py
+++ b/test/test_ssl/test_dhparam.py
@@ -26,7 +26,7 @@ def assert_log_contains(expected_log_line):
     """
     sut_container = docker_client.containers.get("nginxproxy")
     docker_logs = sut_container.logs(stdout=True, stderr=True, stream=False, follow=False)
-    assert expected_log_line in docker_logs
+    assert bytes(expected_log_line, encoding="utf8") in docker_logs
 
 
 def require_openssl(required_version):
@@ -42,7 +42,7 @@ def require_openssl(required_version):
     """
 
     def versiontuple(v):
-        clean_v = re.sub("[^\d\.]", "", v)
+        clean_v = re.sub(r"[^\d\.]", "", v)
         return tuple(map(int, (clean_v.split("."))))
 
     try:
@@ -52,7 +52,7 @@ def require_openssl(required_version):
     else:
         if not command_output:
             raise Exception("Could not get openssl version")
-        openssl_version = command_output.split()[1]
+        openssl_version = str(command_output.split()[1])
         return pytest.mark.skipif(
             versiontuple(openssl_version) < versiontuple(required_version),
             reason="openssl v%s is less than required version %s" % (openssl_version, required_version))
@@ -71,8 +71,8 @@ def test_dhparam_is_not_generated_if_present(docker_compose):
     assert_log_contains("Custom dhparam.pem file found, generation skipped")
 
     # Make sure the dhparam in use is not the default, pre-generated one
-    default_checksum = sut_container.exec_run("md5sum /app/dhparam.pem.default").split()
-    current_checksum = sut_container.exec_run("md5sum /etc/nginx/dhparam/dhparam.pem").split()
+    default_checksum = sut_container.exec_run("md5sum /app/dhparam.pem.default").output.split()
+    current_checksum = sut_container.exec_run("md5sum /etc/nginx/dhparam/dhparam.pem").output.split()
     assert default_checksum[0] != current_checksum[0]
 
 
@@ -89,5 +89,5 @@ def test_web5_dhparam_is_used(docker_compose):
 
     host = "%s:443" % sut_container.attrs["NetworkSettings"]["IPAddress"]
     r = subprocess.check_output(
-        "echo '' | openssl s_client -connect %s -cipher 'EDH' | grep 'Server Temp Key'" % host, shell=True)
-    assert "Server Temp Key: X25519, 253 bits\n" == r
+        f"echo '' | openssl s_client -connect {host} -cipher 'EDH' | grep 'Server Temp Key'", shell=True)
+    assert b"Server Temp Key: X25519, 253 bits\n" == r
diff --git a/test/test_ssl/test_dhparam_generation.py b/test/test_ssl/test_dhparam_generation.py
index 0f5398b..4ba1c53 100644
--- a/test/test_ssl/test_dhparam_generation.py
+++ b/test/test_ssl/test_dhparam_generation.py
@@ -22,7 +22,7 @@ def assert_log_contains(expected_log_line):
     """
     sut_container = docker_client.containers.get("nginxproxy")
     docker_logs = sut_container.logs(stdout=True, stderr=True, stream=False, follow=False)
-    assert expected_log_line in docker_logs
+    assert bytes(expected_log_line, encoding="utf8") in docker_logs
 
 
 ###############################################################################
diff --git a/test/test_ssl/wildcard_cert_and_nohttps/test_wildcard_cert_nohttps.py b/test/test_ssl/wildcard_cert_and_nohttps/test_wildcard_cert_nohttps.py
index 2808dee..1946cc0 100644
--- a/test/test_ssl/wildcard_cert_and_nohttps/test_wildcard_cert_nohttps.py
+++ b/test/test_ssl/wildcard_cert_and_nohttps/test_wildcard_cert_nohttps.py
@@ -1,5 +1,5 @@
 import pytest
-from backports.ssl_match_hostname import CertificateError
+from ssl import CertificateError
 from requests.exceptions import SSLError