AssertJ fails to assert BigDecimal equality without scale

Question

I am running assertions like so:

assertThat(obj.getTotal()).isEqualTo(BigDecimal.valueOf(4))

I am getting

Expecting: <4.00> to be equal to: <4>

so then I tried

assertThat(obj.getTotal()).isEqualTo(BigDecimal.valueOf(4.00))

Expecting: <4.00> to be equal to: <4.0>

I found a workaround in which I would set the scale of expected value 4 to 4.00, but it seems quite irritating that I have to do so for all BigDecimal variables in my tests. Is there a better way from AssertJ that I am unaware of?

Answer 1

You can use isEqualByComparingTo or usingComparator that use BigDecimal.compareTo which compares the actual numeric value. The equals method which is the default assertj uses does the following according to JavaDoc:

Unlike compareTo, this method considers two BigDecimal objects equal only if they are equal in value and scale (thus 2.0 is not equal to 2.00 when compared by this method).

So you can do:

    assertThat(obj.getTotal())
        .usingComparator(BigDecimal::compareTo)
        .isEqualTo(BigDecimal.valueOf(4.00));

or simply:

assertThat(obj.getTotal())
    .isEqualByComparingTo(BigDecimal.valueOf(4.00));

To use with Iterable and extracting assertions:

    assertThat(asList(new Trade("1", new BigDecimal("5.200")), new Trade("2", new BigDecimal("4.00"))))
        .extracting(Trade::getId, Trade::getAmount)
        .usingComparatorForType(BigDecimal::compareTo, BigDecimal.class)
        .usingRecursiveFieldByFieldElementComparator()
        .containsExactlyInAnyOrder(tuple("1", new BigDecimal("5.2")), tuple("2", new BigDecimal("4")));