public void Create_ids_for_units() { var population = new [] { new Unit { Id = "*****@*****.**", TargetGroup = "TG1", VisitDate = DateTime.Parse("2020-02-25") }, new Unit { Id = "*****@*****.**", TargetGroup = "TG2", VisitDate = DateTime.Parse("2020-02-25") }, new Unit { Id = "*****@*****.**", TargetGroup = "TG1", VisitDate = DateTime.Parse("2020-02-25") }, new Unit { Id = "*****@*****.**", TargetGroup = "TG2", VisitDate = DateTime.Parse("2020-02-25") } }; var sampler = new Sampler(); var sample = sampler.CreateIdsForUnits(population); // Units ids should be composed by Id_TargetGroup_VisitDate sample[0].ShouldBe("[email protected]_TG1_2020-02-25"); sample[1].ShouldBe("[email protected]_TG2_2020-02-25"); sample[2].ShouldBe("[email protected]_TG1_2020-02-25"); sample[3].ShouldBe("[email protected]_TG2_2020-02-25"); }