EasyMock Static Method – PowerMock, JUnit 4, TestNG

One of the limitations of EasyMock is that it can’t mock static methods. However, we can use PowerMock EasyMock extension to mock static methods.

EasyMock Static Method – PowerMock

PowerMock is divided into multiple modules to support JUnit and TestNG testing framework. Similarly, there are modules to extend EasyMock and Mockito mocking frameworks.

I will provide an example to mock static method using PowerMock on both JUnit 4 and TestNG frameworks. So we need to import the following artifacts.

• powermock-module-junit4
• powermock-module-testng
• powermock-api-easymock
• junit, testng and easymock for obvious reasons.

I am not using JUnit 5 because PowerMock doesn’t support it yet. I am using the following versions for my examples.

<junit4.version>4.12</junit4.version>
<testng.version>6.14.3</testng.version>
<powermock.version>2.0.0-beta.5</powermock.version>
<java.version>10</java.version>
<easymock.version>3.6</easymock.version>

JUnit PowerMock EasyMock Static Method Example

• First step is to annotate test class with @RunWith(PowerMockRunner.class) annotation.
• Next step is to specify the classes to prepare for testing using PowerMock, for example @PrepareForTest(Utils.class). This has to be done at the class level and we can use its fullyQualifiedNames to specify multiple classes and packages.
• In the test method, use PowerMock.mockStatic() method to mock the static methods of the class.
• Stub the behaviors using EasyMock.expect() method.
• Since we don’t have a mock object, use PowerMock.replayAll() to finalize the setup.
• Use asserts to test the behaviors.
• Use PowerMock.verifyAll() to verify that all the stubbed methods were called.

Let’s say we have a utility class as:

class Utils {

	public static long generateID() {
		return System.currentTimeMillis();
	}
}

Here is the JUnit test to mock the static method and test it.

package com.journaldev.easymock.powermock.staticmethod;

import static org.easymock.EasyMock.*;
import static org.junit.Assert.assertEquals;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import static org.powermock.api.easymock.PowerMock.*;

@RunWith(PowerMockRunner.class)
@PrepareForTest(Utils.class)
public class JUnit4PowerMockEasyMockStaticExample {

	@Test
	public void test_static_method() {
		//PowerMock.mockStatic()
		mockStatic(Utils.class);
		
		expect(Utils.generateID()).andReturn(1000L);
		
		//PowerMock.replayAll()
		replayAll();
		
		assertEquals(1000L, Utils.generateID());
		//PowerMock.verifyAll()
		verifyAll();
	}
}

TestNG PowerMock EasyMock Static Method Example

If you want to use TestNG instead of JUnit-4, then make sure your test class extends PowerMockTestCase class. Also remove the @RunWith annotation. Make necessary changes to other annotations and assert methods.

Below class uses TestNG along with PowerMock to mock static methods using EasyMock.

package com.journaldev.easymock.powermock.staticmethod;

import static org.easymock.EasyMock.*;

import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.testng.PowerMockTestCase;
import org.testng.annotations.Test;

import static org.powermock.api.easymock.PowerMock.*;
import static org.testng.Assert.assertEquals;

@PrepareForTest(Utils1.class)
public class TestNGPowerMockEasyMockStaticExample extends PowerMockTestCase{

	@Test
	public void test_static_method() {
		//PowerMock.mockStatic()
		mockStatic(Utils1.class);
		
		expect(Utils1.generateID()).andReturn(1000L);
		
		//PowerMock.replayAll()
		replayAll();
		
		assertEquals(1000L, Utils1.generateID());
		//PowerMock.verifyAll()
		verifyAll();
	}
}
class Utils1 {

	public static long generateID() {
		return System.currentTimeMillis();
	}
}

Summary

PowerMock is a great extension to EasyMock and Mockito mocking frameworks. It helps us by extending our test cases to mock static methods too.