fix: harden Mattermost plugin gating (#1428) (thanks @damoahdominic)

extensions/mattermost/src/channel.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from "vitest";
+
+import { mattermostPlugin } from "./channel.js";
+
+describe("mattermostPlugin", () => {
+  describe("messaging", () => {
+    it("keeps @username targets", () => {
+      const normalize = mattermostPlugin.messaging?.normalizeTarget;
+      if (!normalize) return;
+
+      expect(normalize("@Alice")).toBe("@Alice");
+      expect(normalize("@alice")).toBe("@alice");
+    });
+
+    it("normalizes mattermost: prefix to user:", () => {
+      const normalize = mattermostPlugin.messaging?.normalizeTarget;
+      if (!normalize) return;
+
+      expect(normalize("mattermost:USER123")).toBe("user:USER123");
+    });
+  });
+
+  describe("pairing", () => {
+    it("normalizes allowlist entries", () => {
+      const normalize = mattermostPlugin.pairing?.normalizeAllowEntry;
+      if (!normalize) return;
+
+      expect(normalize("@Alice")).toBe("alice");
+      expect(normalize("user:USER123")).toBe("user123");
+    });
+  });
+
+  describe("config", () => {
+    it("formats allowFrom entries", () => {
+      const formatAllowFrom = mattermostPlugin.config.formatAllowFrom;
+
+      const formatted = formatAllowFrom({
+        allowFrom: ["@Alice", "user:USER123", "mattermost:BOT999"],
+      });
+      expect(formatted).toEqual(["@alice", "user123", "bot999"]);
+    });
+  });
+});