Dont throw away extra paypal months (#12149)

* Issue 10605 - Don't pointlessly format dates

* fix(10605): Be defensive about setting plan termination dates

test/api/unit/libs/payments/stripe/calculateSubscriptionTerminationDate.test.js

@@ -0,0 +1,81 @@
+import moment from 'moment';
+import calculateSubscriptionTerminationDate from '../../../../../../website/server/libs/payments/calculateSubscriptionTerminationDate';
+import api from '../../../../../../website/server/libs/payments/payments';
+
+const groupPlanId = api.constants.GROUP_PLAN_CUSTOMER_ID;
+
+describe('#calculateSubscriptionTerminationDate', () => {
+  let plan;
+  let nextBill;
+
+  beforeEach(() => {
+    plan = {
+      customerId: 'customer-id',
+      extraMonths: 0,
+    };
+    nextBill = moment();
+  });
+
+  it('should extend date to the exact amount of days left before the next bill will occur', () => {
+    nextBill = moment()
+      .add(5, 'days');
+    const expectedTerminationDate = moment()
+      .add(5, 'days');
+
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+    expect(expectedTerminationDate.diff(terminationDate, 'days')).to.eql(0);
+  });
+
+  it('if nextBill is null, add 30 days to termination date', () => {
+    nextBill = null;
+    const expectedTerminationDate = moment()
+      .add(30, 'days');
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+
+    expect(expectedTerminationDate.diff(terminationDate, 'days')).to.eql(0);
+  });
+
+  it('if nextBill is null and it\'s a group plan, add 2 days instead of 30', () => {
+    nextBill = null;
+    plan.customerId = api.constants.GROUP_PLAN_CUSTOMER_ID;
+    const expectedTerminationDate = moment()
+      .add(2, 'days');
+
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+    expect(expectedTerminationDate.diff(terminationDate, 'days')).to.eql(0);
+  });
+
+  it('should add 30.5 days for each extraMonth', () => {
+    plan.extraMonths = 4;
+    const expectedTerminationDate = moment()
+      .add(30.5 * 4, 'days');
+
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+    expect(expectedTerminationDate.diff(terminationDate, 'days')).to.eql(0);
+  });
+
+  it('should round up if total days gained by extraMonth is a decimal number', () => {
+    plan.extraMonths = 5;
+    const expectedTerminationDate = moment()
+      .add(Math.ceil(30.5 * 5), 'days');
+
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+    expect(expectedTerminationDate.diff(terminationDate, 'days')).to.eql(0);
+  });
+
+  it('behaves like extraMonths is 0 if it\'s set to a negative number', () => {
+    plan.extraMonths = -5;
+    const expectedTerminationDate = moment();
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+    expect(expectedTerminationDate.diff(terminationDate, 'days')).to.eql(0);
+  });
+
+  it('returns current terminated date if it exists and is later than newly calculated date', () => {
+    const expectedTerminationDate = moment().add({ months: 5 }).toDate();
+    plan.terminationDate = expectedTerminationDate;
+
+    const terminationDate = calculateSubscriptionTerminationDate(nextBill, plan, groupPlanId);
+
+    expect(terminationDate).to.equal(expectedTerminationDate);
+  });
+});