.toBeCloseTo(number, numDigits)

Using exact equality with floating point numbers is a bad idea. Rounding means that intuitive things fail. For example, this test fails:

  1. test('adding works sanely with simple decimals', () => {
  2.   expect(0.2 + 0.1).toBe(0.3); // Fails!
  3. });

It fails because in JavaScript, 0.2 + 0.1 is actually 0.30000000000000004. Sorry.

Instead, use .toBeCloseTo. Use numDigits to control how many digits after the decimal point to check. For example, if you want to be sure that 0.2 + 0.1 is equal to 0.3 with a precision of 5 decimal digits, you can use this test:

  1. test('adding works sanely with simple decimals', () => {
  2.   expect(0.2 + 0.1).toBeCloseTo(0.3, 5);
  3. });

The default for numDigits is 2, which has proved to be a good default in most cases.