diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 70c396a..94e4bd6 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -1,3 +1,27 @@
 Contributions are always welcome. Before creating [Pull Requests](https://github.com/52North/WeatherRoutingTool/pulls) or commenting [Issues](https://github.com/52North/WeatherRoutingTool/issues) please carefully read the [Contributing](https://52north.github.io/WeatherRoutingTool/source/guidelines/contribution_guidelines.html) section in our documentation.
 
-Please do not ask if you can work on an issue. Just re-read our documentation and remember that contributions are welcome! Also be aware that we do not assign issues to contributors we have not worked with yet. If this applies to you please do not ask to be assigned. 
\ No newline at end of file
+Please do not ask if you can work on an issue. Just re-read our documentation and remember that contributions are welcome! Also be aware that we do not assign issues to contributors we have not worked with yet. If this applies to you please do not ask to be assigned. 
+
+## Running tests
+
+The test suite uses pytest markers to separate fast unit tests from broader integration tests and optional/manual tests.
+
+### Unit tests
+```bash
+./.venv/bin/pytest -m "unit" -q
+```
+
+### Integration tests
+```bash
+./.venv/bin/pytest -m "integration and not manual and not maripower" -q
+```
+
+### Manual tests
+```bash
+./.venv/bin/pytest -m "manual" -q
+```
+
+### Maripower tests
+```bash
+./.venv/bin/pytest -m "maripower" -q
+```
diff --git a/pytest.ini b/pytest.ini
index f8b7627..8acf383 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -1,11 +1,9 @@
 [pytest]
 
-markers = 
+markers =
+    unit: fast tests for isolated functions/classes
+    integration: tests using configs, datasets, or multiple components
     genetic: tests for genetic algorithm
     maripower: tests that need maripower support
     manual: tests that produce figures as output
 addopts = -ra --tb=short --strict-markers
-
-
-
-	
diff --git a/tests/test_direct_power_method.py b/tests/test_direct_power_method.py
index 7d366ee..ddeda5b 100644
--- a/tests/test_direct_power_method.py
+++ b/tests/test_direct_power_method.py
@@ -22,6 +22,8 @@
 except ModuleNotFoundError:
     pass  # maripower installation is optional
 
+pytestmark = pytest.mark.integration
+
 
 class TestDPM:
     '''
diff --git a/tests/test_genetic.py b/tests/test_genetic.py
index 7042c07..3bfe3f5 100644
--- a/tests/test_genetic.py
+++ b/tests/test_genetic.py
@@ -22,6 +22,8 @@
 from WeatherRoutingTool.ship.ship_config import ShipConfig
 from WeatherRoutingTool.utils.maps import Map
 
+pytestmark = pytest.mark.integration
+
 
 def test_isofuelpatcher_singleton():
     dirname = os.path.dirname(__file__)
diff --git a/tests/test_maripower_tanker.py b/tests/test_maripower_tanker.py
index 3e36fed..97eb02f 100644
--- a/tests/test_maripower_tanker.py
+++ b/tests/test_maripower_tanker.py
@@ -22,6 +22,8 @@
 except ModuleNotFoundError:
     pass  # maripower installation is optional
 
+pytestmark = pytest.mark.integration
+
 
 @pytest.mark.skip(reason="maripower needs update of requirements.")
 # @pytest.mark.skipif(not have_maripower, reason="maripower is not installed")
diff --git a/tests/test_utils.py b/tests/test_utils.py
index dacf5e5..b813281 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -8,6 +8,8 @@
 import WeatherRoutingTool.algorithms.genetic.utils as gen_utils
 from WeatherRoutingTool.utils.maps import Map
 
+pytestmark = pytest.mark.unit
+
 
 def test_get_angle_bins_2greater360():
     min_alpha = 380 * u.degree
diff --git a/tests/test_weather.py b/tests/test_weather.py
index ed3dc34..f19ca2b 100644
--- a/tests/test_weather.py
+++ b/tests/test_weather.py
@@ -2,6 +2,8 @@
 
 from WeatherRoutingTool.weather import WeatherCond
 
+pytestmark = pytest.mark.unit
+
 
 @pytest.mark.parametrize("u,v,theta_res", [(-1, -1, 45), (1, -1, 315), (1, 1, 225), (-1, 1, 135)])
 def test_theta_from_uv(u, v, theta_res):