diff --git a/.azure-pipelines/templates/jobs/extended-tests-jobs.yml b/.azure-pipelines/templates/jobs/extended-tests-jobs.yml
index 48fcae18f..cffedfcb2 100644
--- a/.azure-pipelines/templates/jobs/extended-tests-jobs.yml
+++ b/.azure-pipelines/templates/jobs/extended-tests-jobs.yml
@@ -21,6 +21,8 @@ jobs:
           PYTHON_VERSION: 3.7
           TOXENV: py37
           CERTBOT_NO_PIN: 1
+        linux-external-mock:
+          TOXENV: external-mock
         linux-boulder-v1-integration-certbot-oldest:
           PYTHON_VERSION: 3.6
           TOXENV: integration-certbot-oldest
diff --git a/tox.ini b/tox.ini
index 94cd305aa..fd9105e8b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -137,6 +137,11 @@ commands =
 setenv =
     {[testenv:oldest]setenv}
 
+[testenv:external-mock]
+commands =
+    python {toxinidir}/tools/pip_install.py mock
+    {[base]install_and_test} {[base]all_packages}
+
 [testenv:lint]
 basepython = python3
 # separating into multiple invocations disables cross package