访问实体数据库的单元测试功能

Question

Trying to unit test functions which access a entity framework. So i tried to put all the entity code into the test function below? However it stops at the Linq statement; obviously trying to access the database is too much drama for it. Maybe a work around would be too to create a replica database within the unit test function based on sql lite or compact;(Its not a big database anyways) then execution would not have to leave the test function? Is this possible and how would i implement it?

public void RetreiveKeyFnTest()
    {
        StegApp target = new StegApp(); // TODO: Initialize to an appropriate value
        string username = "david"; // TODO: Initialize to an appropriate value
        string password = "david1"; // TODO: Initialize to an appropriate value
        string ConnectionString = ConfigurationManager.ConnectionStrings["DatabaseEntities"].ToString();
        var dataContext = new DatabaseEntities(ConnectionString);
        var user = dataContext.Users.FirstOrDefault(u => u.Username.Equals(username) && u.Password.Equals(password));
        Assert.IsNotNull(user);

        //target.RetreiveKeyFn(username, password);
        //Assert.IsInstanceOfType(target.RetreiveLogs,typeof(DataAccess));
        //Assert.IsInstanceOfType(target.p);
        //Assert.IsNotNull(target.RetreiveLogs.AuthenitcateCredentials(username,password));
        //Assert.Inconclusive("A method that does not return a value cannot be verified.");
    }

Below is the code i am trying to test:

public void RetreiveKeyFn(string username, string password)
    {

        BusinessObjects.User p = RetreiveLogs.AuthenitcateCredentials(username,password);
        if (p != null)
        {
            if (RetreiveLogs.RetreiveMessages(p.UserId) == null)
            {
                DisplayLogs.Text = "Sorry No messages for you recorded in Database, your correspondant might have chose not to record the entry";
            }
            else
            {
                MessageBox.Show("LogId = " + RetreiveLogs.RetreiveMessages(p.UserId).LogId + "\n" +
                "UserId = " + RetreiveLogs.RetreiveMessages(p.UserId).UserId + "\n" +
                "Message Key = " + RetreiveLogs.RetreiveMessages(p.UserId).MessageKey + "\n" + "PictureId = " + RetreiveLogs.RetreiveMessages(p.UserId).PictureId +
                " Date & time = " + RetreiveLogs.RetreiveMessages(p.UserId).SentDateTime);
                DisplayLogs.Visible = true;
            }
        }
        else
        {
            MessageBox.Show("Please enter your correct username and password in order to retreive either key, image or both from Databse");
        }


    }

Answer 1

First, you should be able to access the same database in your test application as the one you're using in your main/actual application. You just need to make sure that your Test project contains your connection string in its own App.config.

The initialization of the context should be done either inside your StegApp(), or you should be able to pass a context to your StegApp() from a different scope. From what I read of your code, your StegApp() will not be able to access the dataContext variable you created.

Your test for null user already happens inside the RetrieveKeyFn() under the AuthenticateCredentials() method so there's no need for the first "Assert.IsNotNull(user)". I would recommend separating your business logic for RetrieveKeyFn from your UI behaviors so that you can easily do unit tests. You can bind the "Messagebox" operations to say a button click event handler which calls just RetrieveKeyFn(). I would suggest maybe something like this:

public class StegApp
{

      public DatabaseEntities context;
      //other properties

      public StegApp()
      {
           //assuming your DatabaseEntities class inherits from DbContext. 
           //You should create other constructors that allow you to set options
           //like lazy loading and mappings
           this.context = new DatabaseEntities(); 
      } 

      //ASSUMING YOUR RetrieveLogs.RetrieveMessages() function returns 
      //a Message object. replace this type with whatever type the
      //RetrieveLogs.RetrieveMessages() method returns.
      public Message RetrieveKeyFn (string username, string password)
      {

          BusinessObjects.User p = RetreiveLogs.AuthenitcateCredentials(username,password);
          if (p != null)
          {
              var message = RetrieveLogs.RetrieveMessages(p.UserId);
              if (message == null)
                  // handle behavior for no messages. In this case 
                  // I will just create a new Message object with a -1 LogId
                  return new Message {LogId =-1};
              else
                  return message;
          }
          else
              //handle behavior when the user is not authenticated. 
              //In this case I throw an exception
              throw new Exception();

      }

     //on your button click handler, do something like:
     // try 
     // {
     //     var message = RetrieveKeyFn(txtUsername.Text.Trim(), txtPassword.Text.Trim());
     //     if (message.LogId == -1)
     //         DisplayLogs.Text = "Sorry No messages for you recorded in Database, your correspondant might have chose not to record the entry";
     //     else
     //     {
     //         MessageBox.Show("Log Id = " + message.LogId)
     //         etc. etc. etc.
     //     }
     // }
     // catch
     // {
     //       MessageBox.Show ("user is not authenticated");
     // }

}

When you do your unit test, remember to have the appropriate configuration strings in your test project's App.Config If the app.config does not yet exist, go ahead and create one. You should create tests for all possibilities (ie 1) user is valid, you get the message, 2) user is valid, there are no messages, 3) user is invalid).

Here's an example for case 2

    [TestMethod]
    public void RetrieveKeyFnTest1()
    {
        StegApp target = new StegApp(); // this creates your context. I'm assuming it also creates your RetrieveLogs object, etc
        var username = "UserWithNotMessages"; //this user should exist in your database but should not have any messages. You could insert this user as part of your TestInitialize method
        var password = "UserWithNotMessagesPassword"; //this should be the proper password
        var message = target.RetrieveKeyFn(username, password);
        Assert.AreEqual (-1, message.LogId);
    }

Answer 2

I got my unit tests to work fine. The mistake i had was not to copy the app.config file into the test project! Although to be honest i expected Visual studio would have done that anyways.