Asserting Exceptions for private method in JUnit

Question

private static String getToken(HttpClient clientInstance) throws badcredentailsexception{
try{
    // some process here throws IOException
    }
catch(IOexception e){
    throw new badcredentailsexception(message, e)
   }
}

Now I need to write Junit test for the above method, My Junit code for above function is below

@Test(expected = badcredentailsexception.class)
public void testGetTokenForExceptions() throws ClientProtocolException, IOException, NoSuchMethodException, SecurityException, IllegalAccessException, 
                        IllegalArgumentException, InvocationTargetException {

  Mockito.when(mockHttpClient.execute(Mockito.any(HttpPost.class))).thenThrow(IOException.class);
 // mocked mockHttpClient to throw IOException

    final Method method = Client.class.getDeclaredMethod("getToken", HttpClient.class);
    method.setAccessible(true);
    Object actual = method.invoke(null, mockHttpClient);
    }

But this test is not being passed, any improvements??

Can we check the exception thrown by private method from junit ??

1.explain what do you meant by test is not being passed. are you getting any exception? 2. I dont think you can test private methods using Mockito. You should use Powermockito — pvpkiran, Dec 26 '17 at 13:57
The test method invokes `getToken(HttpClient)` but your method doesn't have the `HttpClient` parameter. Is this due to copy/paste or do you have two `getToken`methods? — Roland Weisleder, Dec 26 '17 at 17:34
There needs to be a argument for the function, edited now @RolandWeisleder — harish chava, Dec 27 '17 at 04:52
@pvpkiran I am expecting badcredentailsexception, But I got getting Invocation target exception from method.invoke statement along with bad credentials exception in Junit trace — harish chava, Dec 27 '17 at 05:08
Possible duplicate of [Testing Private method using mockito](https://stackoverflow.com/questions/8799439/testing-private-method-using-mockito) — Stefan Birkner, Jan 12 '18 at 09:55

score 2 · Accepted Answer · answered Dec 27 '17 at 11:31

First of all, it is an antipattern to test a private method. It is not part of your API. See the already linked question: Testing Private method using mockito

To answer your question: When invoking a method via Reflection and the invoked method throws an Exception, the Reflection API wraps the Exception into an InvocationTargetException. So you could catch the InvocationTargetException and inspect the cause.

@Test
public void testGetTokenForExceptions() throws Exception {
    HttpClient mockHttpClient = mock(HttpClient.class);
    when(mockHttpClient.execute(any(HttpPost.class))).thenThrow(IOException.class);

    Method method = Client.class.getDeclaredMethod("getToken", HttpClient.class);
    method.setAccessible(true);

    try {
        method.invoke(null, mockHttpClient);
        fail("should have thrown an exception");
    } catch (InvocationTargetException e) {
        assertThat(e.getCause(), instanceOf(BadCredentialsException.class));
    }
}

score 0 · Answer 2 · answered Dec 26 '17 at 20:50

0

You couldn't test private methods with JUnit or even with Mockito framework. You could find more details in this question: Testing Private method using mockito

If you really need to test this private method, you should use PowerMock framework.

answered Dec 26 '17 at 20:50

Timur Salakhetdinov

1
2

Asserting Exceptions for private method in JUnit

2 Answers2