code: public @NotNull DoubleAssert isEqualTo(double expected, org.fest.assertions.Delta delta) {
      return isEqualTo(expected, delta.doubleValue());
    }
docs: Verifies that the actual {@code Double} is equal to the given one, within a positive delta.
  
  @param expected the value to compare the actual one to.
  @param delta    the given delta.
  @return this assertion object.
  @throws AssertionError if the actual {@code Double} is not equal to the given one.
  @since 1.1