public async Task AddsContentArray()
            {
                // Given
                TestDocument         input      = new TestDocument();
                AddContentToMetadata addContent = new AddContentToMetadata("Foo")
                {
                    new ExecuteConfig(new[] { "Bar", "Baz" })
                };

                // When
                IReadOnlyList <TestDocument> results = await ExecuteAsync(input, addContent);

                // Then
                results.Single()["Foo"].ShouldBe(new[] { "Bar", "Baz" });
            }
            public async Task AddsContentFromDocument()
            {
                // Given
                TestDocument         input      = new TestDocument();
                TestDocument         content    = new TestDocument("Fuzz");
                AddContentToMetadata addContent = new AddContentToMetadata("Foo")
                {
                    new ExecuteConfig(content)
                };

                // When
                IReadOnlyList <TestDocument> results = await ExecuteAsync(input, addContent);

                // Then
                results.Single()["Foo"].ShouldBe("Fuzz");
            }