code: public void toBeCloseTo(double other, double delta) {
  		boolean isCloseTo = this.value >= other - delta && this.value <= other + delta;
  		Expectations.expectTrue(isCloseTo, "Expected %s to be close to %s with delta %s", this.value, other, delta);
  	}
docs: Checks if the stored value is close to another value.
  <p>This method throws an {@code AssertionError} if the difference between the stored value and {@code other} is
  greater than {@code delta}.
  @param other the value to compare with
  @param delta the delta