public async Task ProcessAsync_AlreadyHaveDescriptionThrowsInvalidOperationException()
        {
            // Arrange
            var errorSummaryContext = new ErrorSummaryContext();

            errorSummaryContext.TrySetDescription(attributes: null, new HtmlString("Existing description"));

            var context = new TagHelperContext(
                tagName: "govuk-error-summary-description",
                allAttributes: new TagHelperAttributeList(),
                items: new Dictionary <object, object>()
            {
                { typeof(ErrorSummaryContext), errorSummaryContext }
            },
                uniqueId: "test");

            var output = new TagHelperOutput(
                "govuk-error-summary-description",
                attributes: new TagHelperAttributeList(),
                getChildContentAsync: (useCachedResult, encoder) =>
            {
                var tagHelperContent = new DefaultTagHelperContent();
                tagHelperContent.SetContent("Some description");
                return(Task.FromResult <TagHelperContent>(tagHelperContent));
            });

            var tagHelper = new ErrorSummaryDescriptionTagHelper();

            // Act
            var ex = await Assert.ThrowsAsync <InvalidOperationException>(() => tagHelper.ProcessAsync(context, output));

            Assert.Equal("Cannot render <govuk-error-summary-description> here.", ex.Message);
        }
        public async Task ProcessAsync_AddsDescriptionToContext()
        {
            // Arrange
            var errorSummaryContext = new ErrorSummaryContext();

            var context = new TagHelperContext(
                tagName: "govuk-error-summary-description",
                allAttributes: new TagHelperAttributeList(),
                items: new Dictionary <object, object>()
            {
                { typeof(ErrorSummaryContext), errorSummaryContext }
            },
                uniqueId: "test");

            var output = new TagHelperOutput(
                "govuk-error-summary-description",
                attributes: new TagHelperAttributeList(),
                getChildContentAsync: (useCachedResult, encoder) =>
            {
                var tagHelperContent = new DefaultTagHelperContent();
                tagHelperContent.SetContent("Some description");
                return(Task.FromResult <TagHelperContent>(tagHelperContent));
            });

            var tagHelper = new ErrorSummaryDescriptionTagHelper();

            // Act
            await tagHelper.ProcessAsync(context, output);

            // Assert
            Assert.Equal("Some description", errorSummaryContext.Description?.content.AsString());
        }