Add script for validating PR title (#4050)

.github/scripts/validate-pr-title.test.ts

@@ -0,0 +1,30 @@
+import test from "node:test";
+import { validateTitle } from "./validate-pr-title.ts";
+
+test("validateTitle - missing Android label", (t) => {
+  t.assert.deepEqual(validateTitle({
+    labels: new Set(["android"]),
+    title: "make a change"
+  }), {
+    mismatches: ["android"],
+    ok: false
+  });
+});
+
+test("validateTitle - android required and title contains Android", (t) => {
+  t.assert.deepEqual(validateTitle({
+    labels: new Set(["android"]),
+    title: "make change to Android"
+  }), {
+    ok: true
+  });
+});
+
+test("validateTitle - only core required when label contains core", (t) => {
+  t.assert.deepEqual(validateTitle({
+    labels: new Set(["core", "android"]),
+    title: "core: make some change"
+  }), {
+    ok: true
+  });
+});