public async Task ReplaceWithContent()
            {
                // Given
                const string       search   = @"<html>
                            <head>
                                <title>Foobar</title>
                            </head>
                            <body>
                                <span>fizzbuzz</span>
                            </body>
                        </html>";
                const string       expected = @"<html>
                            <head>
                                <title>Foobar</title>
                            </head>
                            <body>
                                <span>abc123</span>
                            </body>
                        </html>";
                TestDocument       document = new TestDocument("abc123");
                ReplaceWithContent replace  = new ReplaceWithContent("fizzbuzz", Config.FromValue(search));

                // When
                TestDocument result = await ExecuteAsync(document, replace).SingleAsync();

                // Then
                result.Content.ShouldBe(expected);
            }
            public async Task KeepsExistingMediaType()
            {
                // Given
                TestDocument       document = new TestDocument("ABC", "Foo");
                ReplaceWithContent replace  = new ReplaceWithContent("ABC", "123");

                // When
                TestDocument result = await ExecuteAsync(document, replace).SingleAsync();

                // Then
                result.ContentProvider.MediaType.ShouldBe("Foo");
            }