WithIdentityInsert() is found in FluentMigrator.Runner.Extensions. When installing via nuget, this leads you to manually add a reference to FluentMigrator.Runner.dll.
2 problems with that:
1. You should really add the reference by installing FluentMigrator.Tools and using the reference in the Any folder because the main FluentMigrator project has FluentMigrator.Runner.dll set to x86, which causes warnings.
2. As you update between FluentMigrator versions, you need to manually update the reference to the FluentMigrator.Runner.dll in your project to point to the new path location.
I'd like to either see WithIdentityInsert() moved within the main FluentMigrator assembly, or perhaps just install FluentMigrator.Runner.dll as part of the nuget install process (if this is done, please update with the proper configuration settings for x86 and any).
Will be fixed by #437