A clone of the SharePoint client NuGets but with the following changes
- All public member made virtual.
 - A public parameterless constructor added to all public types.
 - Constructors of public type made public.
 - StrongNamed with a new key
 - Un-sealed
 
This results in the public types being mockable for unit testing purposes.
[Fact]
public void CustomMock()
{
    var listItem = new MockListItem
    {
        DisplayNameEx = "The Display Name"
    };
    Assert.Equal("The Display Name", listItem.DisplayName);
}
class MockListItem : ListItem
{
    public override string DisplayName => DisplayNameEx;
    public string DisplayNameEx { get; set; }
}[Fact]
public void FakeItEasy()
{
    var listItem = A.Fake<ListItem>();
    A.CallTo(() => listItem.DisplayName)
        .Returns("The Display Name");
    Assert.Equal("The Display Name", listItem.DisplayName);
}- Alt.SharePoint2013.CSOM
 - Alt.SharePoint2013.CSOM.Min
 - Alt.SharePoint2016.CSOM
 - Alt.SharePoint2016.CSOM.Min
 - Alt.SharePointOnline.CSOM
 - Alt.SharePointOnline.CSOM.Min
 
The .Min variants contain only Microsoft.SharePoint.Client.dll and Microsoft.SharePoint.Client.Runtime.dll.