diff --git a/setup.py b/setup.py
index 185dd67..b7b88a1 100644
--- a/setup.py
+++ b/setup.py
@@ -33,7 +33,7 @@
     install_requires=["attrs~=19.3"],
     extras_require={
         "code_style": ["flake8<3.8.0,>=3.7.0", "black==19.10b0", "pre-commit==1.17.0"],
-        "testing": ["coverage", "pytest>=3.6,<4", "pytest-cov"],
+        "testing": ["coverage", "pytest>=3.6,<4", "pytest-cov", "pytest-regressions"],
         "rtd": ["sphinx>=2,<3", "myst-parser", "pyyaml"],
         "benchmark": ["commonmark~=0.9.1", "markdown~=3.2", "mistune~=0.8.4"],
     },