add pypdf as test dependency

pyproject.toml

@@ -100,7 +100,12 @@ building_docs = ["mkdocs-material==9.5.4", "mkdocstrings-python==1.8.0"]
 
 # For tests, RenderCV uses pytest. Coverage package is used to generate coverage
 # reports.
-testing = ["coverage==7.4.0", "pytest==7.4.4", "time-machine==2.13.0"]
+testing = [
+    "coverage==7.4.0",
+    "pytest==7.4.4",
+    "time-machine==2.13.0",
+    "pypdf==4.0.1",
+]
 
 # Ruff is a linter (a tool to flag stylistic errors, bugs, suspicious constructs, etc.)
 # Black is a code formatter.