public async Task GetAllIdsTest()
        {
            // Arrage
            ServiceIdentityTree tree = this.SetupTree();
            IList <string>      identitiesExpected = new List <string>()
            {
                this.root.Id, this.e1_L1.Id, this.e1_L2.Id, this.e2_L1.Id, this.e2_L2.Id, this.e3_L2.Id, this.e4_L2.Id, this.leaf1.Id, this.leaf2.Id, this.mod1.Id, this.mod2.Id
            };

            // Act
            IList <string> identities = await tree.GetAllIds();

            // Assert
            Assert.Equal(11, identities.Count);
            foreach (string id in identitiesExpected)
            {
                Assert.Contains(id, identities);
            }
        }