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Testing Private Methods

I've been playing with TestNG for a few days now. I really like it. It makes me want to write more tests.

I was wondering if there was a way to create a test for a private method, so I went to the source. I asked Cédric about it. He mentioned that I should use the Reflection API.

The goal was to write a test for the validate method in the following class:

package net.thauvin.erik;

public class Example {
  // ...
  
  private static int validate(String username, String password, int days) {
    // ...
    
    return days;
  }
}

• Retrieve the method using Class.getDeclaredMethod()
• Make it accessible using Method.setAccessible()

package net.thauvin.erik;

import org.testng.annotations.*;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class ExampleTest {
  // ...

  @Test
  public void validateTest() throws NoSuchMethodException,
      IllegalAccessException, InvocationTargetException {
    final Method validate = Example.class.getDeclaredMethod("validate",
        String.class, String.class, int.class);
    validate.setAccessible(true);

    assert (new Integer(10).equals(validate.invoke(validate, "test",
        "passw0rd", new Integer(10))));
  }
}

Tags:  java, tdd, testng