Set up mypy tests

Author: Tinche

pdm.lock

@@ -9,7 +9,6 @@ lint = [
 test = [
     "hypothesis>=6.79.4",
     "pytest>=7.4.0",
-    "pytest-benchmark>=4.0.0",
     "immutables>=0.20",
     "typing-extensions>=4.7.1",
     "coverage>=7.2.7",
@@ -26,6 +25,11 @@ docs = [
 ]
 bench = [
     "pyperf>=2.6.1",
+    "pytest-benchmark>=4.0.0",
+]
+tests-mypy = [
+    "pytest-mypy-plugins>=3.0.0",
+    "mypy>=1.7.1",
 ]
 
 [build-system]
@@ -96,7 +100,7 @@ bson = [
 ]
 
 [tool.pytest.ini_options]
-addopts = "-l --benchmark-sort=fullname --benchmark-warmup=true --benchmark-warmup-iterations=5  --benchmark-group-by=fullname"
+addopts = "-l --mypy-only-local-stub --benchmark-sort=fullname --benchmark-warmup=true --benchmark-warmup-iterations=5  --benchmark-group-by=fullname"
 
 [tool.coverage.run]
 parallel = true