From 85695666b474d321d2908c85702131c0e54cab30 Mon Sep 17 00:00:00 2001
From: Ben Mitchinson <mitchinson.dev@gmail.com>
Date: Sun, 17 Mar 2024 23:15:05 -0500
Subject: [PATCH] Add tests that mock + advance time

---
 README.md                     |  3 +-
 tests/CommonTestOperations.ts | 12 +++++-
 tests/main-page.spec.ts       | 70 ++++++++++++++++++++++++++---------
 3 files changed, 65 insertions(+), 20 deletions(-)

diff --git a/README.md b/README.md
index dcbdd96..be2bb0c 100644
--- a/README.md
+++ b/README.md
@@ -38,6 +38,5 @@ auto-generated categorization table.
 
 ### Next Up
 
-- Need tests that can advance the mock time to test reset / submit sets time to
-  current.
+- Blog post about time mock
 - Need shadcn before adding more features
diff --git a/tests/CommonTestOperations.ts b/tests/CommonTestOperations.ts
index df15fad..899598d 100644
--- a/tests/CommonTestOperations.ts
+++ b/tests/CommonTestOperations.ts
@@ -1,14 +1,19 @@
 import { expect, type Page } from "@playwright/test";
 import { format, parse } from "date-fns";
 
+const formatOfDatetimeFieldValue = "yyyy-MM-dd'T'HH:mm";
+
 export const mockedClockDatetimeString = "2023-05-12T01:30";
 
 export const mockedClockDate = parse(
   mockedClockDatetimeString,
-  "yyyy-MM-dd'T'HH:mm",
+  formatOfDatetimeFieldValue,
   new Date()
 );
 
+export const dateToDatetimeFieldValue = (date: Date) =>
+  format(date, formatOfDatetimeFieldValue);
+
 export const fillPurchaseFormWithValidData = async (page: Page) => {
   await page.getByLabel("Amount").fill("10.77");
   await page.getByLabel("Description").fill("cool trip");
@@ -62,6 +67,11 @@ export const categoryOnForm = async (page: Page) => {
   }
 };
 
+export const advanceTimeOneMinute = async (page: Page) =>
+  await page.evaluate(() => {
+    (window as any).advanceTimeOneMinute();
+  });
+
 export const expectTheseAtPurchaseIndex = async (
   page: Page,
   values: string[],
diff --git a/tests/main-page.spec.ts b/tests/main-page.spec.ts
index 132617e..b974ab9 100644
--- a/tests/main-page.spec.ts
+++ b/tests/main-page.spec.ts
@@ -14,8 +14,10 @@ import {
   expectTheseAtPurchaseIndex,
   mockedClockDate,
   mockedClockDatetimeString,
+  advanceTimeOneMinute,
+  dateToDatetimeFieldValue,
 } from "./CommonTestOperations";
-import { format } from "date-fns";
+import { add, format } from "date-fns";
 
 // TODO: Use shadcn/ui
 
@@ -25,17 +27,21 @@ test.beforeEach(async ({ page }) => {
 
   // Update the Date accordingly in your test pages
   await page.addInitScript(`{
-  // Extend Date constructor to default to fakeNow
+  window.__minutesPassed = 0;
+
+  window.advanceTimeOneMinute = () => {
+    console.log("TIME ADVANCING TO " + ++window.__minutesPassed + " MINUTE(S) PASSED.");
+  }
+
+  Date.now = () => {
+    return ${fakeNow} + window.__minutesPassed * 60000;
+  }
+  
   Date = class extends Date {
     constructor(...args) {
-      (args.length === 0) ? super(${fakeNow}) : super(...args)
+      (args.length === 0) ? super(${fakeNow} + window.__minutesPassed * 60000) : super(...args)
     }
   }
-
-  // Override Date.now() to start from fakeNow
-  const __DateNowOffset = ${fakeNow} - Date.now();
-  const __DateNow = Date.now;
-  Date.now = () => __DateNow() + __DateNowOffset;
 }`);
 
   await clearFirebaseData().then(createFakePurchases);
@@ -77,13 +83,25 @@ test.describe("Entry form", () => {
 
   // todo-postshadcn: add clear button to form
 
-  test("Defaults to the current datetime", async ({ page }) => {});
+  test("Defaults to the current datetime", async ({ page }) => {
+    await advanceTimeOneMinute(page);
+    await advanceTimeOneMinute(page);
+    await page.getByText("Submit").click();
+
+    const expectedTime = add(mockedClockDate, { minutes: 2 });
+    await expect(page.getByTestId("datetime-input")).toHaveValue(
+      new RegExp(dateToDatetimeFieldValue(expectedTime))
+    );
+  });
 });
 
 test.describe("Adding", () => {
-  test("Adding a purchase saves it to the database", async ({ page }) => {
+  test.beforeEach(async ({ page }) => {
     await clearFirebaseData().then(() => page.goto("/"));
     await fillPurchaseFormWithValidData(page);
+  });
+
+  test("Adding a purchase saves it to the database", async ({ page }) => {
     await page.getByText("Submit").click();
 
     await expect(page.getByTestId("purchase-list-item-0")).toContainText(
@@ -95,8 +113,18 @@ test.describe("Adding", () => {
     await expect(page.getByTestId("purchase-list-item-0")).toContainText("Gas");
   });
 
-  // TODO done but needs test
-  // test("Adding a purchase÷ resets date/time to current time");
+  test("Adding a purchase resets date/time to current time", async ({
+    page,
+  }) => {
+    await advanceTimeOneMinute(page);
+    await advanceTimeOneMinute(page);
+    await page.getByText("Submit").click();
+
+    const expectedTime = add(mockedClockDate, { minutes: 2 });
+    await expect(page.getByTestId("datetime-input")).toHaveValue(
+      new RegExp(dateToDatetimeFieldValue(expectedTime))
+    );
+  });
 
   // todo-postshadcn: validation for each field (right now you can just do category)
 });
@@ -217,11 +245,19 @@ test("Tests running in playwright use fake database", async ({ page }) => {
   });
 });
 
-// test.describe("Reset", async ({ page }) => {
-// todo: reset should populate to an updated time, not the time when the page was loaded
-// done but needs test.
-// need a way to advance time a minute
-// });
+test.describe("Reset", () => {
+  test("Reseting updates time in date/time entry", async ({ page }) => {
+    await advanceTimeOneMinute(page);
+    await advanceTimeOneMinute(page);
+
+    await page.getByText("Reset").click();
+
+    const expectedTime = add(mockedClockDate, { minutes: 2 });
+    await expect(page.getByTestId("datetime-input")).toHaveValue(
+      new RegExp(dateToDatetimeFieldValue(expectedTime))
+    );
+  });
+});
 
 // todo: enable some of these tests to run in offline mode
 //     as well?