@Test
  void isBlankInputNotNullOutputFalse() {
    // Arrange
    final String value = "AAAAAAAA";
    // Act
    final boolean retval = Util.isBlank(value);
    // Assert result
    assertThat(retval).isEqualTo(false);
  }
Ex. your {@code Foo} object would be null, but so would things like Number.
core/src/test/java/feign/UtilTest.java