Fix faulty tests for createAppointment (#2767)

* fix: correct implementation of `createAppointment`

Makes the suggested implementation of `createAppointment` correctly handle appointment creations that
cross timezones - e.g. due to Daylight Savings Time.

re: https://forum.exercism.org/t/tests-and-suggested-implementation-for-appointment-time-are-wrong/

* fix: correct tests for `createAppointment`

Corrects the test so that they respect locales with Daylight Savings Time.

Previously, tests and suggested implementation simply did simple time arithmetic based on the offset
provided to `createAppointment`. This is wrong, as it will shift appointment time-of-day when moving
accross DST boundaries. This changes test implementation so that:
1. correct usage of input times is checked, by passing a 0 offset
2. correct offsetting of appointment time is checked, by passing in a known start date and then
creating one appointment that is within the same DST state and one that is not.

re: https://forum.exercism.org/t/tests-and-suggested-implementation-for-appointment-time-are-wrong/

* docs: update hints

* chore: update contributors

* style: prettier

* docs: refer to instructions for going about getter method

Co-authored-by: Cool-Katt <[email protected]>

* docs: more concise hint about setters

Co-authored-by: Cool-Katt <[email protected]>

* Format all the things

---------

Co-authored-by: Cool-Katt <[email protected]>
Co-authored-by: Derk-Jan Karrenbeld <[email protected]>

Author: 3 people

.prettierignore

@@ -1,7 +1,9 @@
 /.github/labels.yml
-/.github/workflows/sync-labels.yml
-/.github/workflows/no-important-files-changed.yml
+
+# Generated
 exercises/**/README.md
+pnpm-lock.yaml
+
 !/README.md
 
 # Originates from https://github.com/exercism/org-wide-files
@@ -19,4 +21,4 @@ config.json
 
 # Originates from https://github.com/exercism/problem-specifications
 exercises/practice/**/.docs/instructions.md
-exercises/practice/**/.docs/introduction.md
+exercises/practice/**/.docs/introduction.md

exercises/concept/appointment-time/.docs/hints.md

@@ -4,7 +4,8 @@
 
 - You need to create a new date. The introduction elaborates on the different ways.
 - `Date.now()` gives you current time in milliseconds
-- A day consist of 24 hour. An hour consist of 60 minutes. A minute consist of 60 seconds. A second consist of 1000 milliseconds. In order to get timestamp of `n` days later from current date, you can sum current timestamp and `n * 24 * 60 * 60 * 1000`.
+- `Date` has several getter methods, listed in the introduction, to get date components. Can you use one of those methods?
+- Likewise, `Date` has matching setter methods to set those components, rolling over into "higher" components if needed.
 
 ## 2. Convert a date into a timestamp
 

exercises/concept/appointment-time/.meta/config.json

@@ -3,6 +3,9 @@
     "SalahuddinAhammed",
     "SleeplessByte"
   ],
+  "contributors": [
+    "BadIdeaException"
+  ],
   "files": {
     "solution": [
       "appointment-time.js"

exercises/concept/appointment-time/.meta/exemplar.js

@@ -9,7 +9,10 @@
  * @returns {Date} the appointment
  */
 export function createAppointment(days, now = Date.now()) {
-  return new Date(now + days * 24 * 3600 * 1000);
+  const date = new Date(now);
+  date.setDate(date.getDate() + days);
+
+  return date;
 }
 
 /**

exercises/concept/appointment-time/appointment-time.spec.js

@@ -10,33 +10,45 @@ import {
 } from './appointment-time';
 
 describe('createAppointment', () => {
-  test('creates appointment 4 days in the future', () => {
-    const currentTime = Date.now();
-    const expectedTime = currentTime + 345600 * 1000;
+  test('uses the passed in current time', () => {
+    const currentTime = Date.UTC(2000, 6, 16, 12, 0, 0, 0);
+    const result = createAppointment(0, currentTime);
 
-    expect(createAppointment(4, currentTime)).toEqual(new Date(expectedTime));
+    expect(result).toEqual(new Date(currentTime));
   });
 
-  test('creates appointment 124 in the future', () => {
+  test('uses the actual current time when it is not passed in', () => {
     const currentTime = Date.now();
-    const expectedTime = currentTime + 10713600 * 1000;
+    const result = createAppointment(0);
 
-    expect(createAppointment(124, currentTime)).toEqual(new Date(expectedTime));
+    expect(result).toEqual(new Date(currentTime));
   });
 
-  test('uses the passed in current time', () => {
-    const currentTime = Date.UTC(2000, 6, 16, 12, 0, 0, 0);
-    const result = createAppointment(0, currentTime);
+  test('creates appointment without DST change', () => {
+    const offset = 4; // days
 
-    expect(result.getFullYear()).toEqual(2000);
+    const currentTime = Date.UTC(2000, 6, 1, 12, 0, 0, 0);
+    const expectedTime = currentTime + offset * 24 * 60 * 60 * 1000;
+
+    expect(createAppointment(offset, currentTime)).toEqual(
+      new Date(expectedTime),
+    );
   });
 
-  test('uses the actual current time when it is not passed in', () => {
-    const result = createAppointment(0);
+  test('creates appointment with potential DST change', () => {
+    const offset = 180; // days
+
+    const currentTime = Date.UTC(2000, 6, 1, 12, 0, 0, 0);
+    let expectedTime = currentTime + offset * 24 * 60 * 60 * 1000;
+    // Manually adjust for DST timezone offset:
+    expectedTime +=
+      (new Date(expectedTime).getTimezoneOffset() -
+        new Date(currentTime).getTimezoneOffset()) *
+      60 *
+      1000;
 
-    expect(Math.abs(Date.now() - result.getTime())).toBeLessThanOrEqual(
-      // Maximum number of time zones difference
-      27 * 60 * 60 * 1000,
+    expect(createAppointment(offset, currentTime)).toEqual(
+      new Date(expectedTime),
     );
   });