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Cape Town | 25-ITP-MAY | Asanda Dunn | Sprint 1 | Exhaustively test and fix formatAs12HourClock #1630

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Cape Town | 25-ITP-MAY | Asanda Dunn | Sprint 1 | Exhaustively test and fix formatAs12HourClock #1630

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15 changes: 12 additions & 3 deletions format-clock-edge-cases/timeConverter.js
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Original file line number Diff line number Diff line change
@@ -1,11 +1,20 @@
function formatAs12HourClock(time) {

const hours = Number(time.slice(0, 2));
const minutes = time.slice(3);

@cjyuan cjyuan Oct 4, 2026

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Note: The .slice() method supports negative indices, which count positions from the end of the string.

For example, str.slice(-3) returns the substring containing last three characters from str.


if (hours === 0) {
return `12:${minutes} am`;
}

if (hours === 12) {
return `12:${minutes} pm`;
}

if (hours > 12) {
return `${hours - 12}:00 pm`;
return `${hours - 12}:${minutes} pm`;
}

return `${time} am`;
}

export {formatAs12HourClock};
export { formatAs12HourClock };
54 changes: 49 additions & 5 deletions format-clock-edge-cases/timeConverter.test.js
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@cjyuan cjyuan Oct 4, 2026

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Some tests are duplicated.

Original file line number Diff line number Diff line change
@@ -1,11 +1,55 @@
import {formatAs12HourClock} from "./timeConverter.js";
import { formatAs12HourClock } from "./timeConverter.js";
import assert from "node:assert";
import test from "node:test";

test("correctly convert time after 12:00", function(){
assert.equal(formatAs12HourClock("23:00"), "11:00 pm");
test("correctly convert time after 12:00", function () {
assert.equal(formatAs12HourClock("23:00"), "11:00 pm");
});

test("can correctly convert morning time", function() {
assert.equal(formatAs12HourClock("08:00"), "08:00 am");
test("can correctly convert morning time", function () {
assert.equal(formatAs12HourClock("08:00"), "08:00 am");
});

test("correctly convert time after 12:00", function () {
assert.equal(formatAs12HourClock("23:00"), "11:00 pm");
});

test("can correctly convert morning time", function () {
assert.equal(formatAs12HourClock("08:00"), "08:00 am");
});

test("can correctly convert midnight", function () {
assert.equal(formatAs12HourClock("00:00"), "12:00 am");
});

test("can correctly convert midday", function () {
assert.equal(formatAs12HourClock("12:00"), "12:00 pm");
});

test("can correctly convert 12:30 pm", function () {
assert.equal(formatAs12HourClock("12:30"), "12:30 pm");
});
Comment on lines +21 to +31

@cjyuan cjyuan Oct 4, 2026

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Could also test "preservation of minutes" in the midnight case.


test("preserves minutes in the morning", function () {
assert.equal(formatAs12HourClock("09:45"), "09:45 am");
});

test("preserves minutes in the afternoon", function () {
assert.equal(formatAs12HourClock("13:45"), "1:45 pm");
});
Comment on lines +33 to +39

@cjyuan cjyuan Oct 4, 2026

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If "09:45" is converted to "09:45 am", it is probably reasonable for the caller to expect "13:45" to be converted to "01:45 pm".

When the returned values are not formatted consistently, it may result in unintended side-effect. For examples,

  1. When the strings are displayed, "01:00 pm" and "1:00 pm" would not align as nicely.
01:00 am
1:00 pm
12:00 am
01:00 pm
  1. When the formatted strings are compared in the program, "1:00 pm" < "11:00 pm" and 01:00 am" < "11:00 am" produce different results.

Consistency is important so the caller can be certain what to expect from a function.


test("correctly converts 1:00 pm", function () {
assert.equal(formatAs12HourClock("13:00"), "1:00 pm");
});

test("correctly converts 6:30 pm", function () {
assert.equal(formatAs12HourClock("18:30"), "6:30 pm");
});

test("correctly converts 11:59 pm", function () {
assert.equal(formatAs12HourClock("23:59"), "11:59 pm");
});

test("correctly converts 11:59 am", function () {
assert.equal(formatAs12HourClock("11:59"), "11:59 am");
});
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