Same as SoftAssertions, but with the following differences:
First, it's a junit rule, which can be used without having to call assertAll(), example:

 public class SoftlyTest {

    @Rule
    public final JUnitSoftAssertions softly = new JUnitSoftAssertions();

    @Test
    public void testSoftly() throws Exception {
      softly.assertThat(1).isEqualTo(2);
      softly.assertThat(Lists.newArrayList(1, 2)).containsOnly(1, 2);
    }
 }

Second, the failures are recognized by IDE's (like IntelliJ IDEA) which open a comparison window.