Content Search

You can mock a Sitecore.ContentSearch.ISearchIndex so that it returns a Sitecore.Data.Items.Item:

[Fact]
public void HowToMockContentSearchLogic()
{
  try
  {
    var index = Substitute.For<Sitecore.ContentSearch.ISearchIndex>();
    Sitecore.ContentSearch.ContentSearchManager.SearchConfiguration.Indexes
      .Add("my_index", index);

    using (Sitecore.FakeDb.Db db = new Sitecore.FakeDb.Db
      {
        new Sitecore.FakeDb.DbItem("home")
      })
    {
      var searchResultItem =
        Substitute.For<Sitecore.ContentSearch.SearchTypes.SearchResultItem>();

      searchResultItem
        .GetItem()
        .Returns(db.GetItem("/sitecore/content/home"));

      index
        .CreateSearchContext()
        .GetQueryable<Sitecore.ContentSearch.SearchTypes.SearchResultItem>()
        .Returns((new[] { searchResultItem }).AsQueryable());

      Sitecore.Data.Items.Item result =
        index
        .CreateSearchContext()
        .GetQueryable<Sitecore.ContentSearch.SearchTypes.SearchResultItem>()
        .Single()
        .GetItem();

      Xunit.Assert.Equal("/sitecore/content/home", result.Paths.FullPath);
    }
  }
  finally
  {
    Sitecore.ContentSearch.ContentSearchManager.SearchConfiguration.Indexes
      .Remove("my_index");
  }
}