diff --git a/environment.yml b/environment.yml
index b6af3f4..c82dc48 100644
--- a/environment.yml
+++ b/environment.yml
@@ -21,6 +21,7 @@ dependencies:
   - pandas
   - Pillow
   - pytest
+  - pytest-mock
   - python-dotenv
   - scikit-learn
   - scikit-image
diff --git a/pyproject.toml b/pyproject.toml
index 9c7d292..bc6162f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,7 +31,7 @@ dependencies = [
 
 [project.optional-dependencies]
 jupyter = ["jupyterlab", "jupytext", "matplotlib", "scikit-learn"]
-test = ["pytest", "pytest-cov", "parameterized"]
+test = ["pytest", "pytest-cov", "pytest-mock", "parameterized"]
 lint = ["flake8", "isort", "ruff"]
 pipeline = ["luigi", "fastapi", "uvicorn"]
 all = ["cyto_ml[jupyter,test,lint,pipeline]"]