使用第三方API调用的构造函数的JUnit

Question

Below mentioned is the class that I need to test:

public class MyClass {
     private String key;
     public MyClass(Connection con) {
         key = ThirdPartyApi.getkey(con);
     }
     public String getKey() {
         return key;
     }
}

Now I need to test this constructor, but am unable to mock this Third party API call. And the Test case would be as mentioned below :

public class MyClassTest{
 @Test
 public void test1(){
     MyClass c = new MyClass(dummyconnection);
     assertNotNull(c.getKey != null);
 }
}

But this case would be giving me an error that ThirdPartyAPI Class is failing as the the connection object is mocked.

So I want to mock this ThirdPartyApi call. Is it possible using Easymock, powermock?

Answer 1

Simple: EasyMock does not support mocking static calls. So you can turn to PowerMock(ito) or JMockit in case you do not want to change your code.

But the better approach would be to understand that using static always leads to tight coupling between your classes, and that you want to make sure that this doesn't affect your ability to unit test your code.

In your case:

public MyClass(Connection con) {
  key = ThirdPartyApi.getkey(con);

simply replace that with:

public MyClass(Connection con) {
  this (ThirdPartyApi.getkey(con));
}

/** unit testing only */
MyClass(Key key) {
  ...

And voila, you got a constructor that you can call from your unit test - and now you simply pass a mocked key object. And your tests will no longer execute that static call - because you use the key-taking constructor in all your tests.

But you probably want another test case to make sure that calling the public constructor does what you expect it to do - and that could be to throw an exception because that static call fails.

Beyond that: I fully agree with the comments - the fact that your constructor is doing so much (including static calls) has a certain design smell on it.