Sheffield | 25-ITP-Sep | Jak Rhodes-Smith | Sprint 1 | Data Groups #912
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Code is working great.
I only have a few suggestions.
| // Then it should return a copy of the original array | ||
| test("given an array with no duplicates, it returns a copy of the original array", () => { | ||
| expect(dedupe([1, 2, 3])).toEqual([1, 2, 3]); | ||
| expect(dedupe(["a", "b", "c"])).toEqual(["a", "b", "c"]); | ||
| }); |
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This test is expected to check also whether the returned array is a copy of the original array --
that is, whether the argument and the returned value of dedupe(array) are two different arrays.
The following test only checks whether both arrays contain the same elements;
it cannot check whether the arrays are actually different objects:
expect(array1).isEqual(array2);
Suggestion: Find out how to test whether two arrays are different arrays in Jest.
| const numbers = elements | ||
| .filter((val) => typeof val === "number") | ||
| .sort((a, b) => a - b); |
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- Sorting is unnecessary before calling
Math.max() - Could also consider filter out
NaN(also a value of type number)
| test("given an array with decimal numbers, returns correct sum", () => { | ||
| expect(sum([10.5, 20.3, 5.2])).toBe(36); | ||
| }); |
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Decimal numbers in most programming languages (including JavaScript) are internally represented in floating-point format.
Floating-point arithmetic is not exact. For example, the expression 46.5678 - 46 === 0.5678 evaluates to false
because 46.5678 - 46 produces a value that is only very close to 0.5678, not exactly equal.
Even changing the order in which numbers are added or subtracted can lead to slightly different results.
So the following could happen
expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.805 ); // This will fail
expect( 1.2 + 0.6 + 0.005 ).toEqual( 1.8049999999999997 ); // This will pass
expect( 0.005 + 0.6 + 1.2 ).toEqual( 1.8049999999999997 ); // This will fail
console.log(1.2 + 0.6 + 0.005 == 1.805); // false
console.log(1.2 + 0.6 + 0.005 == 0.005 + 0.6 + 1.2); // falseCan you find a more appropriate way to test a value (that involves decimal-number calculations) for equality?
Suggestion: Look up
- how to check equality in floating-point arithmetic in JavaScript
- how to check equality in floating-point arithmetic using Jest
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