What is @Factory Annotation ?

TestNG Factory annotation feature allows us to create tests dynamically at run-time.Factory will execute all the @Test methods in the test class using a separate instance of the test class.

We will go through a code example to explain about @Factory annotated method.

package com.testingdocs.testng.sample;

import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

public class FactoryExampleClass 
{
  String testdata ;
  int objectID ;
  
  public FactoryExampleClass(int ojectID, String testdata)
  {
    this.objectID = ojectID ;
    this.testdata= testdata ;
  }
  
  @BeforeClass 
   public void beforeClass(){ 
    System.out.println("This is before class of " + objectID); 
   } 
  
  @Test 
   public void testmethod(){ 
    System.out.println("This is test method, testdata is  :" + testdata); 
   }
  
  @AfterClass 
   public void afterClass(){ 
    System.out.println("This is after class of " +  objectID); 
   } 

}

 

Now we would write @Factory method which runs for 3 times as shown below.

package com.testingdocs.testng.sample;

import org.testng.annotations.Factory;

public class TestNGFactory 
{
  
  @Factory
  public static Object[] testData()
  { 
    Object[] object = new Object[3]; 
     
    object[0]= new FactoryExampleClass(1,"testdata1"); 
    object[1]= new FactoryExampleClass(2,"testdata2"); 
    object[2]= new FactoryExampleClass(3,"testdata3"); 
    		   
    return object; 
   } 
}

 

Run result:

This is before class of 1
This is test method, testdata is  :testdata1
This is after class of 1
This is before class of 3
This is test method, testdata is  :testdata3
This is after class of 3
This is before class of 2
This is test method, testdata is  :testdata2
This is after class of 2

PASSED: testmethod
PASSED: testmethod
PASSED: testmethod

===============================================
Default test
Tests run: 3, Failures: 0, Skips: 0
===============================================

Look how we have executed the test method multiple times run-time for different testdata . ( 3 times in the above example )

Common problems is exceptions in Factory methods.Any exception in the factory method would throw an exception like as shown below sample exception trace.:

org.testng.TestNGException:
The factory method class com.testingdocs.testng.sample.TestNGFactory.testData() threw an exception

We need to debug the root cause of the exception in the factory method.TestNG internal code that displays the error is as shown below:

 

catch (Throwable t) {
      ConstructorOrMethod com = getConstructorOrMethod();
      throw new TestNGException("The factory method "
          + com.getDeclaringClass() + "." + com.getName()
          + "() threw an exception", t);
    }