Add tests for the new resource

test/resources/BillingPortal/Sessions.spec.js

@@ -0,0 +1,27 @@
+'use strict';
+
+const stripe = require('../../../testUtils').getSpyableStripe();
+
+const expect = require('chai').expect;
+
+describe('BillingPortal', () => {
+  describe('Sessions Resource', () => {
+    describe('create', () => {
+      it('Sends the correct request', () => {
+        const params = {
+          customer: 'cus_123',
+          return_url: 'https://stripe.com/return',
+        };
+        stripe.billingPortal.sessions.create(params);
+
+        expect(stripe.LAST_REQUEST).to.deep.equal({
+          method: 'POST',
+          url: '/v1/billing_portal/sessions',
+          headers: {},
+          data: params,
+          settings: {},
+        });
+      });
+    });
+  });
+});