如何使用 Entity Framework Core 为 sqlite 编写代码第一个单元测试？

Question

I'm trying to do a very simple rest api for starters. I created the local sqlite file using the tool and it works. Now I want to write a unit test for the database.

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

namespace dz1
{
    [Table("User")]
    public class User
    {
        [Key]
        [Column]
        public string Name { get; set; }

        [Column]
        public string Address { get; set; }

        [Column]
        public int Age { get; set; }
    }

    [Table("News")]
    public class News
    {
        [Key]
        [Column]
        public string Title { get; set; }

        [Column]
        public string Content { get; set; }

        [Column]
        [ForeignKey("User")]
        public string Author { get; set; }
    }

    public class MyContext : DbContext
    {
        private readonly string _connectionString;

        public MyContext()
        {
            this._connectionString = "DataSource=./mydb.db";
        }

        public MyContext(string connectionString)
        {
            this._connectionString = connectionString;
        }

        public DbSet<User> Users { get; set; }
        public DbSet<News> News { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlite(_connectionString);
        }
    }
}

and my unit test code:

using System;
using System.Linq;
using dz1;
using Xunit;

namespace ApiTest
{
    public class UnitTest1
    {
        [Fact]
        public void Test1()
        {
            var ctx = new MyContext("DataSource=:memory:");

            ctx.Database.EnsureDeleted();
            ctx.Database.EnsureCreated();

            var u = new User();
            u.Name = "Mirko";
            u.Address = "Tamo 2";
            u.Age = 101;

            ctx.Users.Add(u);
            ctx.SaveChanges();

            Assert.True(ctx.Users.ToList().First().Name == "Mirko");
        }
    }
}

I read on the internets that EnsureCreated should be enough to create the tables in the in-memory database. What am I missing?

I get an error

Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details. ---- Microsoft.Data.Sqlite.SqliteException: SQLite Error 1: 'no such table: User'.

How do I force the tables to get created?

I even tried using

            RelationalDatabaseCreator databaseCreator =
                (RelationalDatabaseCreator) ctx.Database.GetService<IDatabaseCreator>();

            var s = databaseCreator.GenerateCreateScript();

            ctx.Database.ExecuteSqlRaw(s);

but I don't get it. Does the sql script even doesn't run?

Answer 1

Follow these steps, you should be able to get it working.

1) Create SQLite connection for in-memory database

2) Create the DbContextOptions for SQlite connection

3) Pass the DbContextOptions to the DataContext. For this you need to have a overload in the DataContext accepting a DbContextOptions.

4) Call the dbContext.Database.EnsureCreated() to create the database.

using(var connection = new SqliteConnection("DataSource=:memory:"))
{
    connection.Open();
    var options = new DbContextOptionsBuilder<DataContext>()
                   .UseSqlite(connection)                  
                   .Options;

    var dbContext = new DataContext(options);
    dbContext.Database.EnsureCreated();

    //You testing logic goes here.
}

5) Adding a overload constructor in DataContext

public DataContext(DbContextOptions<DataContext> options) : base(options)
{

}

6) Database will be deleted with disposing the connection

You can find a code sample in https://github.com/Wijithapaw/PMS/tree/sqlite/PMS.Api

Cheers,