运行测试，又会出现红条了，测试失败。现在要考虑实现一个真正的在数据库中的查找功能，怎么开始做呢?当然还是由测试开始，有了上面的基础，现在写的测试跨库可以稍微大点：

[TestFixture]

public class CustomerDAOTests

{

[Test]

public void ShouldFoundCustomerByID()

{

string id = "ALFKI";

string comName = "Alfreds Futterkiste";

CustomerDAO customerDAO = new CustomerDAO();

Customer found = customerDAO.FindCustomerByID(id);

Assert.That(found， Is.Not.Null);

Assert.That(found.CustomerID， Is.EqualTo(id));

Assert.That(found.CompanyName， Is.EqualTo(comName));

id = "AROUT";

comName = "Around the Horn";

found = customerDAO.FindCustomerByID(id);

Assert.That(found， Is.Not.Null);

Assert.That(found.CustomerID， Is.EqualTo(id));

Assert.That(found.CompanyName， Is.EqualTo(comName));

}

}

这段代码不能编译，因为并没有CustomerDAO这个类，所以得新增该类以及FindCustomerByID方法，而且上面的测试中已经包括了两个测试场景，现在可以直接写实现：

public class CustomerDAO

{

public Customer FindCustomerByID(string id)

{

using (NorthwindDataContext ctx = new NorthwindDataContext())

{

IQueryable customers = ctx.Customers.Where(c => c.CustomerID == id);

if (customers.Count() > 0)

return customers.Single();

else

return null;

}

}

}

运行一下该测试，通过!然后再将aspx.cs里面的代码进行改动使Web页面的测试通过

void btn_find_customer_Click(object sender， EventArgs e)

{

string id = tb_customerID.Text;

Customer c = customerDAO.FindCustomerByID(id);

if (c == null)

return;

lbl_customerID.Text = c.CustomerID;

lbl_companyName.Text = c.CompanyName;

pnl_customerInfo.Visible = true;

}