diff --git a/setup.cfg b/setup.cfg
index df38962..db1f87c 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -38,6 +38,7 @@ install_requires =
     pytest-arraydiff>=0.1
     pytest-filter-subpackage>=0.1
     pytest-cov>=2.0
+    pytest-mock>=2.0
     hypothesis>=5.1
     # We don't include the following for now since it brings in
     # matplotlib as a dependency.