diff --git a/setup.py b/setup.py
index 4ac3425..2edfe4a 100644
--- a/setup.py
+++ b/setup.py
@@ -107,7 +107,8 @@ def read(rel_path):
     extras_require={
         # Note that "lofar-utils" also depends on the python bindings to the LOFAR ParmDB.
         # Since these have never been published on PyPI, we cannot specify this dependency.
-        "lofar-utils": ["losoto"]
+        "lofar-utils": ["losoto"],
+        "dev": ["pytest", "pytest-cov", "ruff", "pre-commit"],
     },
     entry_points={
         "console_scripts": [
diff --git a/tests/__init__.py b/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/tests/test_formatters.py b/tests/test_formatters.py
new file mode 100644
index 0000000..3807909
--- /dev/null
+++ b/tests/test_formatters.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+"""
+Tests for the formatters module
+"""
+
+from datetime import datetime, timedelta
+import random
+from RMextract.formatters import KNOWN_FORMATTERS, ftp_aiub_unibe_ch, cddis_gsfc_nasa_gov, igsiono_uwm_edu_pl, chapman_upc_es
+
+def test_known_formatters():
+    """
+    Test that the known formatters are correct
+    """
+    assert KNOWN_FORMATTERS["ftp.aiub.unibe.ch"] == ftp_aiub_unibe_ch
+    assert KNOWN_FORMATTERS["cddis.gsfc.nasa.gov"] == cddis_gsfc_nasa_gov
+    assert KNOWN_FORMATTERS["igsiono.uwm.edu.pl"] == igsiono_uwm_edu_pl
+    assert KNOWN_FORMATTERS["http://chapman.upc.es"] == chapman_upc_es
+
+def test_ftp_aiub_unibe_ch():
+    """
+    Test the ftp_aiub_unibe_ch formatter
+    """
+    for server in ["ftp://ftp.aiub.unibe.ch", "file://ftp.aiub.unibe.ch"]:
+        year = random.randint(2000, 2024)
+        dayofyear = random.randint(1, 366)
+        prefix = "CODG"
+        url = ftp_aiub_unibe_ch(server, year, dayofyear, prefix)
+        expected = f"{server}/CODE/{year:4d}/{prefix.upper()}{dayofyear:03d}0.{year%100:02d}I.Z"
+        assert url == expected, f"Expected {expected}, got {url}"
+
+def test_cddis_gsfc_nasa_gov():
+    """
+    Test the cddis_gsfc_nasa_gov formatter
+    """
+    for server in ["ftp://cddis.gsfc.nasa.gov", "file://cddis.gsfc.nasa.gov"]:
+        year = random.randint(2000, 2024)
+        dayofyear = random.randint(1, 366)
+        prefix = "CODG"
+        url = cddis_gsfc_nasa_gov(server, year, dayofyear, prefix)
+        expected = f"{server}/gnss/products/ionex/{year:4d}/{dayofyear:03d}/{prefix.lower()}{dayofyear:03d}0.{year%100:02d}i.Z"
+        assert url == expected, f"Expected {expected}, got {url}"
+
+def test_igsiono_uwm_edu_pl():
+    """
+    Test the igsiono_uwm_edu_pl formatter
+    """
+    for server in ["ftp://igsiono.uwm.edu.pl", "file://igsiono.uwm.edu.pl"]:
+        year = random.randint(2000, 2024)
+        dayofyear = random.randint(1, 366)
+        prefix = "IGRG"
+        url = igsiono_uwm_edu_pl(server, year, dayofyear, prefix)
+        expected = f"{server}/data/ilt/{year:4d}/{prefix.lower()}{dayofyear:03d}0.{year%100:02d}i"
+        assert url == expected, f"Expected {expected}, got {url}"
+
+def test_chapman_upc_es():
+    """
+    Test the chapman_upc_es formatter
+    """
+    for server in ["http://chapman.upc.es", "file://chapman.upc.es"]:
+        year = random.randint(2000, 2024)
+        dayofyear = random.randint(1, 366)
+        prefix = "CODG"
+        url = chapman_upc_es(server, year, dayofyear, prefix)
+        dt = datetime(year,1,1) + timedelta(dayofyear-1)
+        expected = f"{server}/tomion/rapid/{year:4d}/{dayofyear:03d}_{year%100:02d}{dt.month:02d}{dt.day:02d}.15min/{prefix.lower()}{dayofyear:03d}0.{year%100:02d}i.Z"
+        assert url == expected, f"Expected {expected}, got {url}"
\ No newline at end of file