[tests][iid] added iid() tests -> 100% coverage

bridge/e2e/iid/iid.e2e.js

@@ -0,0 +1,22 @@
+describe('iid()', () => {
+  describe('get()', () => {
+    it('returns instance id string', async () => {
+      const iid = await firebase.iid().get();
+      iid.should.be.a.String();
+    });
+  });
+
+  describe('delete()', () => {
+    it('deletes the current instance id', async () => {
+      const iidBefore = await firebase.iid().get();
+      iidBefore.should.be.a.String();
+
+      await firebase.iid().delete();
+
+      const iidAfter = await firebase.iid().get();
+      iidAfter.should.be.a.String();
+
+      iidBefore.should.not.equal(iidAfter);
+    });
+  });
+});