public async Task InsertRandomData()
{
//Arrange
var dbSet = Substitute.For <DbSet <DefaultModel> >();
var context = Substitute.For <DefaultContext>();
context.DefaultModels = dbSet;
var controller = new DefaultController(context);
//Act
await controller.GenerateData();
//Assert
dbSet.Received(1).Add(Arg.Any <DefaultModel>());
await context.Received(1).SaveChangesAsync();
}