模拟测试 SqlDataReader 结果

Question

我有一个与员工合作的应用程序。所以我决定使用 Mock 来测试 Employee Repository。

这是我的测试方法

class EmployeesRepository : IEmployeeRepository ...

public IEnumerable<Employee> GetAllEmployees()
{
    List<Employee> list = new List<Employee>();

    try
    {           
        string connectionString = _secureConfig.Value.MyDbSetting;
        
        string sql = "select id, firstname, lastname, entrydate, email from empoyees";
        using SqlConnection connection = new SqlConnection(connectionString);
        using SqlCommand command = new SqlCommand(sql, connection);
        connection.Open();

        using SqlDataReader reader = command.ExecuteReader();
        while (reader.Read())
        {
            list.Add(new Employee
            {
                Id = reader.GetString(0),
                FirstName = reader.GetString(1),
                LastName = reader.GetString(2),
                EntryDate = reader.GetDateTime(3),
                Email = (reader.IsDBNull(4) ? null : reader.GetString(4))
            });
        }
    }
    catch (Exception ex)
    {
        _log.LogError(ex, "An error is caught when getting all employees");
    }
    return list;
}

我的问题是在这种情况下模拟什么以及如何模拟......我应该模拟数据读取器，还是只模拟 ExecutReader 方法......请提供建议，从哪里开始测试这些方法并直接访问数据库。

Answer 1

与实现细节/问题的紧密耦合使得这很难单独进行单元测试。

重构依赖于可以模拟的抽象。

例如

class EmployeesRepository : IEmployeeRepository {
    private readonly IDbConnectionFactory dbConnectionFactory;
    //...

    public EmployeesRepository(IDbConnectionFactory dbConnectionFactory /*,...*/) {
        this.dbConnectionFactory = dbConnectionFactory;

        //...
    }

    public IEnumerable<Employee> GetAllEmployees() {
        List<Employee> list = new List<Employee>();

        try {
            string connectionString = _secureConfig.Value.MyDbSetting;
            string sql = "select id, firstname, lastname, entrydate, email from empoyees";

            using (IDbConnection connection = dbConnectionFactory.CreateConnection(connectionString)) {
                using (IDbCommand command = connection.CreateCommand()) {
                    command.CommandText = sql;

                    connection.Open();

                    using (IDataReader reader = command.ExecuteReader()) {
                        while (reader.Read()) {
                            list.Add(new Employee {
                                Id = reader.GetString(0),
                                FirstName = reader.GetString(1),
                                LastName = reader.GetString(2),
                                EntryDate = reader.GetDateTime(3),
                                Email = (reader.IsDBNull(4) ? null : reader.GetString(4))
                            });
                        }
                    }
                }
            }
        } catch (Exception ex) {
            _log.LogError(ex, "An error is caught when getting all employees");
        }
        return list;
    }
}

IDbConnectionFactory 定义为

public interface IDbConnectionFactory {
    ///<summary>
    ///  Creates a connection based on the given database name or connection string.
    ///</summary>
    IDbConnection CreateConnection(string nameOrConnectionString);
}

将在您的 DI 容器中注册的运行时实现如下所示

class SqlConnectionFactory : IDbConnectionFactory {
    public IDbConnection CreateConnection(string nameOrConnectionString) {
        return new SqlConnection(nameOrConnectionString);
    }
}


//...

services.AddSingleton<IDbConnectionFactory, SqlConnectionFactory>();

//...

为了测试上述内容，可以根据需要模拟抽象

public void ShouldGetAllEmployees() {
    //Arrange

    var readerMock = new Mock<IDataReader>();
    //...setup reader members as needed
    
    var commandMock = new Mock<IDbCommand>();
    commandMock.Setup(m => m.ExecuteReader())
        .Returns(readerMock.Object);

    var connectionMock = new Mock<IDbConnection>();
    connectionMock.Setup(m => m.CreateCommand())
        .Returns(commandMock.Object);
    //..Setup...

    var connectionFactoryMock = new Mock<IDbConnectionFactory>();
    connectionFactoryMock
        .Setup(m => m.CreateConnection(It.IsAny<string>()))
        .Returns(connectionMock.Object);

    EmployeesRepository sut = new EmployeesRepository(connectionFactoryMock.Object);

    //Act
    IEnumerable<Employee> actual = sut.GetAllEmployees();

    //Assert
    //...assert desired behavior
}