SourceID.NET -- Nunit

When trying to build project SourceId.Tests, there are 30 errors -- "the
type or namespace name 'Assert' could not be found".
 
The ReadMe references Nunit 2.0 and that is the version available for
download at  <http://nunit.org/>  <http://nunit.org/.> http://nunit.org/.
However, SourceId.Tests.csproj looks like it's referencing Nunit 2.1.  Is it
possible this project is referencing a newer version that's not available
for download yet?
 
Removing the project from the solution allows me to move on, so this is not
major.
 
Thanks.
Karl.

SourceID.NET v.2 Alpha (06/27/2003)
Windows XP Professional SP1
.NET Framework 1.1 (v1.1.4322)
Visual Studio .NET 2003 (v7.1.3088)