public async Task PrependWithNullableDecimalSourceWithElementIsEquivalentToPrependTest()
        {
            // Arrange

            // Arrange 'queryAdapter' parameter
            var queryAdapter = await GetQueryAdapterAsync(DisallowAll);

            // Arrange 'source' parameter
            var source = GetQueryable <decimal?>();

            // Arrange 'asyncSource' parameter
            var asyncSource = queryAdapter.GetAsyncQueryable <decimal?>();

            // Arrange 'element' parameter
            var element = 5;

            // Arrange 'expectedResult' parameter
            var expectedResult =
                Enumerable
                .Prepend <decimal?>(source, element);

            // Act
            var result = await AsyncQueryable.Prepend <decimal?>(asyncSource, element).ToListAsync().ConfigureAwait(false);

            // Assert
            Assert.Equal(expectedResult, result);
        }
        public async Task PrependWithDoubleSourceWithElementNullSourceThrowsArgumentNullExceptionTest()
        {
            // Arrange

            // Arrange 'queryAdapter' parameter
            var queryAdapter = await GetQueryAdapterAsync(DisallowAll);

            // Arrange 'asyncSource' parameter
            IAsyncQueryable <double> asyncSource = null !;

            // Arrange 'element' parameter
            var element = 5;

            // Act
            // -

            // Assert
            await Assert.ThrowsAsync <ArgumentNullException>(async() =>
            {
                await AsyncQueryable.Prepend <double>(asyncSource, element).ToListAsync().ConfigureAwait(false);
            });
        }