diff --git a/jobrunner/config.py b/jobrunner/config.py
index f61b1bee..c3283ead 100644
--- a/jobrunner/config.py
+++ b/jobrunner/config.py
@@ -86,15 +86,21 @@ def _is_valid_backend_name(name):
 
 DOCKER_REGISTRY = os.environ.get("DOCKER_REGISTRY", "ghcr.io/opensafely-core")
 
-db_names = ["full", "default", "include_t1oo"]
-DATABASE_URLS = {
-    db_name: db_url
-    for db_name, db_url in [
-        (db_name, os.environ.get("{db_name.upper()}_DATABASE_URL"))
-        for db_name in db_names
-    ]
-    if db_url
-}
+
+def database_urls_from_env(env):
+    db_names = ["full", "default", "include_t1oo"]
+    return {
+        db_name: db_url
+        for db_name, db_url in [
+            (db_name, env.get(f"{db_name.upper()}_DATABASE_URL"))
+            for db_name in db_names
+        ]
+        if db_url
+    }
+
+
+DATABASE_URLS = database_urls_from_env(os.environ)
+
 
 TEMP_DATABASE_NAME = os.environ.get("TEMP_DATABASE_NAME")
 
diff --git a/tests/test_config.py b/tests/test_config.py
index ca0ab3df..a25a464b 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -5,7 +5,7 @@
 
 import pytest
 
-from jobrunner.config import _is_valid_backend_name
+from jobrunner.config import _is_valid_backend_name, database_urls_from_env
 
 
 script = """
@@ -113,3 +113,16 @@ def test_config_presto_paths_not_exist(tmp_path):
 )
 def test_is_valid_backend_name(name, is_valid):
     assert _is_valid_backend_name(name) == is_valid
+
+
+def test_database_urls_from_env():
+    db_urls = database_urls_from_env(
+        {
+            "DEFAULT_DATABASE_URL": "mssql://localhost/db1",
+            "INCLUDE_T1OO_DATABASE_URL": "mssql://localhost/db2",
+        }
+    )
+    assert db_urls == {
+        "default": "mssql://localhost/db1",
+        "include_t1oo": "mssql://localhost/db2",
+    }