diff --git a/cads_adaptors/adaptors/mars.py b/cads_adaptors/adaptors/mars.py
index 05acd32c..d3b51550 100644
--- a/cads_adaptors/adaptors/mars.py
+++ b/cads_adaptors/adaptors/mars.py
@@ -46,15 +46,37 @@ def convert_format(
     return paths
 
 
+def get_mars_server_list(config) -> list[str]:
+    if config.get("mars_servers") is not None:
+        return ensure_list(config["mars_servers"])
+
+    # TODO: Refactor when we have a more stable set of mars-servers
+    if os.getenv("MARS_API_SERVER_LIST") is not None:
+        default_mars_server_list = os.getenv("MARS_API_SERVER_LIST")
+    else:
+        for default_mars_server_list in [
+            "/etc/mars/mars-api-server-legacy.list",
+            "/etc/mars/mars-api-server.list",
+        ]:
+            if os.path.exists(default_mars_server_list):
+                break
+
+    mars_server_list: str = config.get("mars_server_list", default_mars_server_list)
+    if os.path.exists(mars_server_list):
+        with open(mars_server_list) as f:
+            mars_servers = f.read().splitlines()
+    else:
+        raise SystemError(
+            "MARS servers cannot be found, this is an error at the system level."
+        )
+    return mars_servers
+
+
 def execute_mars(
     request: Union[Request, list],
     context: Context,
     config: dict[str, Any] = dict(),
     target: str = "data.grib",
-    # mars_cmd: tuple[str, ...] = ("/usr/local/bin/mars", "r"),
-    mars_server_list: str = os.getenv(
-        "MARS_API_SERVER_LIST", "/etc/mars/mars-api-server.list"
-    ),
 ) -> str:
     from cads_mars_server import client as mars_client
 
@@ -63,13 +85,7 @@ def execute_mars(
         requests, _cacheable = implement_embargo(requests, config["embargo"])
     context.add_stdout(f"Request (after embargo implemented): {requests}")
 
-    if os.path.exists(mars_server_list):
-        with open(mars_server_list) as f:
-            mars_servers = f.read().splitlines()
-    else:
-        raise SystemError(
-            "MARS servers cannot be found, this is an error at the system level."
-        )
+    mars_servers = get_mars_server_list(config)
 
     cluster = mars_client.RemoteMarsClientCluster(urls=mars_servers, log=context)
 
diff --git a/tests/data/mars_servers.list b/tests/data/mars_servers.list
new file mode 100644
index 00000000..b723a39d
--- /dev/null
+++ b/tests/data/mars_servers.list
@@ -0,0 +1 @@
+http://a-test-server.url
diff --git a/tests/test_15_mars.py b/tests/test_15_mars.py
index b90e824a..4ab2abfc 100644
--- a/tests/test_15_mars.py
+++ b/tests/test_15_mars.py
@@ -1,21 +1,26 @@
-# import pytest
+import os
 
-# from cads_adaptors.adaptors import mars
+from cads_adaptors.adaptors import mars
 
 
-# @pytest.mark.parametrize(
-#     "cmd,error_msg",
-#     (
-#         ("cat r; echo error 1>&2; exit 1", "MARS has crashed."),
-#         ("cat r; touch data.grib; echo error 1>&2", "MARS returned no data."),
-#     ),
-# )
-# def test_execute_mars_errors(tmp_path, monkeypatch, cmd, error_msg):
-#     monkeypatch.chdir(tmp_path)  # execute_mars generates files in the working dir
-#     context = mars.Context()
-#     with pytest.raises(RuntimeError, match=error_msg):
-#         mars.execute_mars(
-#             {},
-#             context=context,
-#             mars_cmd=("bash", "-c", cmd),
-#         )
+def test_get_mars_servers():
+    mars_servers = mars.get_mars_server_list(
+        {"mars_servers": "http://b-test-server.url"}
+    )
+    assert len(mars_servers) == 1
+    assert mars_servers[0] == "http://b-test-server.url"
+
+
+def test_get_mars_servers_list_file():
+    mars_servers = mars.get_mars_server_list(
+        {"mars_server_list": "tests/data/mars_servers.list"}
+    )
+    assert len(mars_servers) == 1
+    assert mars_servers[0] == "http://a-test-server.url"
+
+
+def test_get_mars_servers_envvar():
+    os.environ["MARS_API_SERVER_LIST"] = "tests/data/mars_servers.list"
+    mars_servers = mars.get_mars_server_list({})
+    assert len(mars_servers) == 1
+    assert mars_servers[0] == "http://a-test-server.url"