add more tests

Contributions.md

@@ -8,21 +8,41 @@ In any case, before submitting a PR, please run test locally to validate your PR
 
 ## Syntax/Code Test
 
-### Run "flake8"
+### Preparation
+
+Install required packages, e.g. on Fedora Linux
+
+```
+yum install python3-flake8 python3-isort python3-mypy python3-pytest python3-pytest-isort python3-typeguard
+```
+
+### Tests
+
+#### Run "flake8"
 
 ```
 flake8
 ...
 ```
+No error should be reported!
 
-### Run "isort"
+#### Run "isort"
 
 ```
 isort --check --diff .
 ...
 ```
+No error should be reported!
 
-### Run "pytest"
+### Run "mypy"
+
+```
+python -c 'import importlib.util, subprocess, sys; importlib.util.find_spec("mypy") and sys.exit(subprocess.run(["mypy", "."]).returncode) or print("Skipped: mypy is not installed")'
+...
+```
+No error should be reported!
+
+#### Run "pytest"
 
 ```
 python3 setup.py build || exit 1