public void ValidateDoubleToBeOneOfExpectedValues()
        {
            // Given
            var validator = new DoubleValidator(42);

            // When
            validator.BeOneOf(new double[] { 10, 42 });

            // Then
            Assert.True(true);
        }
        public void ValidateDoubleToBeOneOfViolated()
        {
            // Given
            var validator = new DoubleValidator(42);

            // When
            var exception = Assert.Throws <XunitException>(() => validator.BeOneOf(new double[] { 13, 39 }, because: "that's the bottom line"));

            // Then
            Assert.NotNull(exception);
            var rn = Environment.NewLine;

            Assert.Equal(
                $"{rn}validator{rn}is \"42\"{rn}but was expected to be one of the following values: \"13\", \"39\"{rn}because that's the bottom line",
                exception.UserMessage);
        }