public async Task GetGroupById_Test()
        {
            // Arrange
            var teamsService = new TeamsService(this.dbContext);

            this.dbContext.Groups.Add(new Group {
                Name = "D"
            });
            await this.dbContext.SaveChangesAsync();

            // Act
            var group = teamsService.GetGroupById(1);

            // Assert
            Assert.AreNotEqual(null, group);
        }