diff --git a/tests/test_selfupdate.py b/tests/test_selfupdate.py
new file mode 100644
index 0000000..943f82a
--- /dev/null
+++ b/tests/test_selfupdate.py
@@ -0,0 +1,43 @@
+import json
+import unittest
+
+from mudfish_decky.selfupdate import LATEST_RELEASE_API, latest_plugin_release
+
+RELEASE = {
+    "tag_name": "v0.1.2",
+    "assets": [
+        {"name": "notes.txt", "browser_download_url": "https://git.example/notes.txt"},
+        {"name": "mudfish-decky-0.1.2.zip",
+         "browser_download_url": "https://git.sejong.dev/ysj7705/mudfish-decky/releases/download/v0.1.2/mudfish-decky-0.1.2.zip"},
+    ],
+}
+
+
+class SelfUpdateTest(unittest.TestCase):
+    def test_reads_latest_release_zip(self):
+        urls = []
+
+        def fetch(url):
+            urls.append(url)
+            return json.dumps(RELEASE)
+
+        self.assertEqual(latest_plugin_release(fetch), {
+            "version": "0.1.2",
+            "url": "https://git.sejong.dev/ysj7705/mudfish-decky/releases/download/v0.1.2/mudfish-decky-0.1.2.zip",
+        })
+        self.assertEqual(urls, [LATEST_RELEASE_API])
+        self.assertEqual(LATEST_RELEASE_API,
+                         "https://git.sejong.dev/api/v1/repos/ysj7705/mudfish-decky/releases/latest")
+
+    def test_none_when_release_has_no_zip(self):
+        self.assertIsNone(latest_plugin_release(lambda url: json.dumps({"tag_name": "v1", "assets": []})))
+
+    def test_none_when_unreachable(self):
+        def fetch(url):
+            raise OSError("offline")
+
+        self.assertIsNone(latest_plugin_release(fetch))
+
+
+if __name__ == "__main__":
+    unittest.main()