add more tests for Global task joiner; such as one work item and no work items
add more tests for Global task joiner; such as one work item and no work items

uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,buaasun/grappa,buaasun/grappa,uwsampa/grappa,buaasun/grappa,buaasun/grappa,uwsampa/grappa,alexfrolov/grappa,uwsampa/grappa,alexfrolov/grappa,buaasun/grappa,buaasun/grappa,uwsampa/grappa,uwsampa/grappa,alexfrolov/grappa,alexfrolov/grappa,buaasun/grappa,alexfrolov/grappa,alexfrolov/grappa