added a bit of documentation on how to run tests (#165)

* added a bit of documentation on how to run tests

* formatting

* formatting

* formatting

* formatting

* formatting

* formatting

README.rst

@@ -293,6 +293,36 @@ To install DSMR Parser:
 
     $ pip install dsmr-parser
 
+Development
+-----------
+
+Create a virtualenv and activate it followed by the installation of the dsmr-parser:
+
+.. code-block:: bash
+
+    python3 -m venv venv
+    source venv/bin/activate
+    pip install -e .
+
+Install tox and run it:
+
+.. code-block:: bash
+
+    pip install tox
+    tox
+
+You should see that the tests have succeeded:
+
+.. code-block:: text
+
+    ======================================================================================================== 59 passed in 0.91s ========================================================================================================
+    py: commands[1]> pylama dsmr_parser test
+      py: OK (11.55=setup[9.73]+cmd[1.29,0.53] seconds)
+      congratulations :) (11.69 seconds)
+
+
+Now you can make changes by editing the code and rerunning tox to verify your changes.
+
 Known issues
 ------------