diff --git a/src/tests/gateway/test_get_decompressed_message.py b/src/tests/gateway/test_get_decompressed_message.py
new file mode 100644
index 0000000..e3d2f35
--- /dev/null
+++ b/src/tests/gateway/test_get_decompressed_message.py
@@ -0,0 +1,25 @@
+"""Tests for eddn.Gateway.get_decompressed_message."""
+import os
+from typing import Callable
+
+
+def test_plain_message(eddn_message: Callable, monkeypatch) -> None:
+    """Test eddn.Gateway.get_decompressed_message() with a plain message."""
+    # Tests don't include the directory that `pytest` is run from on sys.path
+    print(type(monkeypatch))
+    monkeypatch.syspath_prepend(os.getcwd())
+    import eddn.Gateway
+
+    eddn.Gateway.setup_bottle_app()
+    print(f'{eddn.Gateway.app.__dict__=}')
+
+    msg = eddn_message('plain_journal_scan_valid')
+
+    dc_msg = eddn.Gateway.get_decompressed_message(
+        {
+            'Content-Type': 'application/json',
+        },
+        msg.encode(encoding='utf-8'),
+    )
+
+    assert msg == dc_msg.decode()