public async Task ExistsShouldReturnCorrectValue(string modelName, bool expected) { var options = new DbContextOptionsBuilder <NeedForCarsDbContext>() .UseInMemoryDatabase("ModelExistsDb") .Options; var context = new NeedForCarsDbContext(options); var makesService = new MakesService(context); var modelsService = new ModelsService(context, makesService); var make = new Make { Name = "Make", Description = "Desc" }; await context.Makes.AddAsync(make); await context.SaveChangesAsync(); var model = new Model { Name = "Model1", Description = "Desc", MakeId = make.Id }; await context.Models.AddAsync(model); await context.SaveChangesAsync(); var result = modelsService.Exists(make.Id, modelName); Assert.Equal(expected, result); }