code: public void toBeBetween(double lower, double upper) {
  		Arguments.ensureTrue(lower < upper, "upper has to be greater than lower");
  		boolean isBetween = this.value >= lower && this.value <= upper;
  		Expectations.expectTrue(isBetween, "Expected %s to be between %s and %s", this.value, lower, upper);
  	}
docs: Checks if the stored value is between a lower and an upper bound.
  <p>This method throws an {@code AssertionError} if:
  <ul>
  <li>the stored value is smaller than the lower bound</li>
  <li>the stored value is greater than the upper bound</li>
  </ul>
  <p>It is ok if the stored value is equal to the lower or the upper bound
  @param lower the lower bound
  @param upper the upper bound
  @throws java.lang.IllegalArgumentException if {@code lower} is not smaller than {@code upper}