diff --git a/.github/workflows/install_and_test.yml b/.github/workflows/install_and_test.yml
index 982c9089d..a23887e4b 100644
--- a/.github/workflows/install_and_test.yml
+++ b/.github/workflows/install_and_test.yml
@@ -33,3 +33,8 @@ jobs:
         run: pytest
       - name: Run CLI
         run: pyspdxtools -i ./tests/spdx/data/formats/SPDXJSONExample-v2.3.spdx.json
+
+      - name: Install optional dependencies
+        run: python -m pip install networkx
+      - name: Run tests for graph generation
+        run: pytest tests/spdx/test_graph_generation.py
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 653b366fa..4c4a04341 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -34,8 +34,10 @@ Here's the process to make changes to the codebase:
    git checkout -b fix-or-improve-something
    python -m venv ./venv
    ./venv/bin/activate
-   pip install -e .
+   pip install -e ".[development]"
    ```
+   Note: By using the group `[development]` for the installation, all dependencies (including optional ones) will be 
+   installed. This way we make sure that all tests are executed. 
 5. Make some changes and commit them to the branch:
    ```sh
    git commit --signoff -m 'description of my changes'
@@ -49,14 +51,12 @@ Here's the process to make changes to the codebase:
    retroactively signs a range of past commits.
 6. Test your changes:
    ```sh
-   pip install pytest
    pytest -vvs # in the repo root
    ```
 
 7. Check your code style. When opening a pull request, your changes will automatically be checked with `isort`, `black` 
    and `flake8` to make sure your changes fit with the rest of the code style. 
     ```sh
-   pip install .[code_style]
    # run the following commands in the repo root
    isort src tests 
    black src tests
diff --git a/pyproject.toml b/pyproject.toml
index 338339c31..7acbb7ffa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -31,6 +31,7 @@ dynamic = ["version"]
 test = ["pytest"]
 code_style = ["isort", "black", "flake8"]
 graph_generation = ["pygraphviz", "networkx"]
+development = ["black", "flake8", "isort", "networkx", "pytest"]
 
 [project.scripts]
 pyspdxtools = "spdx.clitools.pyspdxtools:main"
diff --git a/tests/spdx/test_graph_generation.py b/tests/spdx/test_graph_generation.py
index 6c28d1d41..9128625f2 100644
--- a/tests/spdx/test_graph_generation.py
+++ b/tests/spdx/test_graph_generation.py
@@ -15,7 +15,6 @@
 
 try:
     import networkx  # noqa: F401
-    import pygraphviz  # noqa: F401
 except ImportError:
     pytest.skip("Skip this module as the tests need optional dependencies to run.", allow_module_level=True)
 
@@ -44,7 +43,7 @@
         (
             "SPDXRdfExample-v2.2.spdx.rdf.xml",
             20,
-            17,
+            19,
             ["SPDXRef-Package_DYNAMIC_LINK", "SPDXRef-JenaLib_CONTAINS"],
         ),
         (