Unit Testing – How to Unit Test a Class Requiring Web Service Call

integration-teststddunit testingweb services

I'm trying to test a class which calls some Hadoop web services. The code is pretty much of the form:

method() {
    ...use Jersey client to create WebResource...
    ...make request...
    ...do something with response...
}

e.g. there is a create directory method, a create folder method etc.

Given that the code is dealing with an external web service that I don't have control over, how can I unit test this? I could try and mock the web service client/responses but that breaks the guideline I've seen a lot recently: "Don't mock objects you don't own". I could set up a dummy web service implementation – would that still constitute a "unit test" or would it then be an integration test? Is it just not possible to unit test at this low a level – how would a TDD practitioner go about this?

Best Answer

In my opinion you should mock the webservice calls if this is a unit test, as opposed to an integration test.

Your unit test should not test whether the external webservice is working, or whether your integration with it is correct. Without getting too dogmatic about TDD, note that a side effect of turning your unit test into an integration test is that it's likely to run slower, and you want fast unit tests.

Also, if the webservice is temporarily down or working incorrectly, should this cause your unit test to fail? It doesn't seem right. Your unit test should fail for only one reason: if there is a bug in the code in that "unit".

The only portion of code that is relevant here is ...do something with response.... Mock the rest.

Related Solutions

Php – unit/integration testing web service proxy client

Unfortunately I am not familiar with PHP or PHPUnit; so I apologize if this answer may end up not so useful.

I have experience of trying to do testing in the style you are suggesting and I found it to quickly become a large problem. Integration tests which integrate with the DB must ensure that either after every test, or before ever test that the db is in a known good state. Without this you will get lots of false results. To do it can be an annoying problem. In either case it will take time and be slow.

If your layer is in fact a thin layer which takes a some data from the web and push it to the db layer after (possibly) some modification, validation, etc - I would strongly suggest decoupling it from both the web and from the DB. Mock both ends in your tests. Your tests will be small and fast. Test separately your db layer to ensure it does the right thing when your translation layer tells it to do something.

Since I am not familiar with PHP or PHPUnit I can't help you on how to decouple and mock these items, unfortunately.

Unit Testing – How to Unit Test a Web Client

Unit tests should run fast and have no external dependencies. Integration tests should cover methods that call web services.

You cannot unit test authentication logic on the client, you will have to do it on the server:

[WebMethod]
Authenticator{
 bool Login(Credentials credentials){
   return TestableClass.Login(credentials);
 }
}

now you can write a unit test on the server

Login_WithValidCredentials_ReturnsTrue(){
   // test TestableClass.login here
}

You can also test client side code that uses the service. say you have some code like this: (pardon my c#)

Class LoggerOnner{
  public LoggerOnner(IClient client, Response response){
    this.client = client
    this.page = page
  }

  Login() {
   if(this.client.Authenticate())
       response.sendPage("authenticated.aspx");
   else{
       response.sendError()
   }
  }
}

You can test that it uses your Client correctly (how i imagine moc works :)

IClient mocClient= moq.Create(IClient).Authenticate( x-> return true );
Request moxRequest = moq.Create(Request);

LoggerOnner lo = new LoggerOnner(mocClient, mocRequest);

Assert( mocRequst.sendPage().calledWithArgs("authenticated.aspx"));

TLDR; don't unit test your Client class, make it small and test everything else

Best Answer

Related Solutions

Php – unit/integration testing web service proxy client

Unit Testing – How to Unit Test a Web Client

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