The publish command is currently missing from the IYarnRunnerCommands. This leads to a somewhat inconsistent usage.

context.Yarn().FromPath(file.GetDirectory()).Install();
context.Yarn().FromPath(file.GetDirectory()).RunScript("build");
context.Yarn().FromPath(file.GetDirectory()).RunScript("test");

and

context.Yarn().Publish(settings => settings.WorkingDirectory = file.GetDirectory());