SystemClassUserTest.java

/*
 * Copyright 2008 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package samples.powermockito.junit4.system;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.invocation.InvocationOnMock;
import org.mockito.stubbing.Answer;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import samples.system.SystemClassUser;

import java.net.URL;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.UUID;

import static org.junit.Assert.*;
import static org.mockito.BDDMockito.given;
import static org.mockito.Matchers.anyLong;
import static org.mockito.Mockito.times;
import static org.powermock.api.mockito.PowerMockito.*;

/**
 * Demonstrates PowerMockito's ability to mock non-final and final system
 * classes. To mock a system class you need to prepare the calling class for
 * testing. I.e. let's say you're testing class A which interacts with
 * URLEncoder then you would do:
 * 
 * <pre>
 * 
 * @PrepareForTest({A.class})
 * 
 * </pre>
 */
@RunWith(PowerMockRunner.class)
@PrepareForTest({ SystemClassUser.class })
public class SystemClassUserTest {

	@Test
	public void assertThatMockingOfNonFinalSystemClassesWorks() throws Exception {
		mockStatic(URLEncoder.class);

		when(URLEncoder.encode("string", "enc")).thenReturn("something");

		assertEquals("something", new SystemClassUser().performEncode());

	}

	@Test
	public void assertThatMockingOfTheRuntimeSystemClassWorks() throws Exception {
		mockStatic(Runtime.class);

		Runtime runtimeMock = mock(Runtime.class);
		Process processMock = mock(Process.class);

		when(Runtime.getRuntime()).thenReturn(runtimeMock);
		when(runtimeMock.exec("command")).thenReturn(processMock);

		assertSame(processMock, new SystemClassUser().executeCommand());
	}

	@Test
	public void assertThatMockingOfFinalSystemClassesWorks() throws Exception {
		mockStatic(System.class);

		when(System.getProperty("property")).thenReturn("my property");

		assertEquals("my property", new SystemClassUser().getSystemProperty());
	}

	@Test
	public void assertThatPartialMockingOfFinalSystemClassesWorks() throws Exception {
		spy(System.class);

		when(System.nanoTime()).thenReturn(2L);

		new SystemClassUser().doMoreComplicatedStuff();

		assertEquals("2", System.getProperty("nanoTime"));
	}

	@Test
	public void assertThatMockingOfCollectionsWork() throws Exception {
		List<?> list = new LinkedList<Object>();
		mockStatic(Collections.class);

		Collections.shuffle(list);

		new SystemClassUser().shuffleCollection(list);

		verifyStatic(times(2));
		Collections.shuffle(list);
	}

	@Test
	public void assertThatPartialMockingOfFinalSystemClassesWorksForNonVoidMethods() throws Exception {
		spy(System.class);

		when(System.getProperty("property")).thenReturn("my property");

		final SystemClassUser systemClassUser = new SystemClassUser();
		systemClassUser.copyProperty("to", "property");
	}

	@Test
	public void assertThatMockingStringWorks() throws Exception {
		mockStatic(String.class);
		final String string = "string";
		final String args = "args";
		final String returnValue = "returnValue";

		when(String.format(string, args)).thenReturn(returnValue);

		final SystemClassUser systemClassUser = new SystemClassUser();
		assertEquals(systemClassUser.format(string, args), returnValue);
	}

	@Test
	public void mockingStaticVoidMethodWorks() throws Exception {
		mockStatic(Thread.class);
		doNothing().when(Thread.class);
		Thread.sleep(anyLong());

		long startTime = System.currentTimeMillis();
		final SystemClassUser systemClassUser = new SystemClassUser();
		systemClassUser.threadSleep();
		long endTime = System.currentTimeMillis();
		assertTrue(endTime - startTime < 5000);
	}

	@Test
	public void mockingURLWorks() throws Exception {
		URL url = mock(URL.class);
		URLConnection urlConnectionMock = mock(URLConnection.class);

		when(url.openConnection()).thenReturn(urlConnectionMock);

		URLConnection openConnection = url.openConnection();

		assertSame(openConnection, urlConnectionMock);
	}

    @Test
    public void mockingUUIDWorks() throws Exception {
        // given
        final UUID mock = mock(UUID.class);
        mockStatic(UUID.class);
        given(UUID.randomUUID()).willReturn(mock);

		// when
		String actual = new SystemClassUser().generatePerishableToken();

		// then
		assertEquals("00000000000000000000000000000000", actual);
    }

    @Test
    public void mockingNewURLWorks() throws Exception {
        // Given
        final URL url = mock(URL.class);
        whenNew(URL.class).withArguments("some_url").thenReturn(url);

        // When
        final URL actual = new SystemClassUser().newURL("some_url");

        // Then
        assertSame(url, actual);
    }

	@Test
	public void mockingStringBuilder() throws Exception {
        // Given
		 final StringBuilder mock = mock(StringBuilder.class);
		 whenNew(StringBuilder.class).withNoArguments().thenReturn(mock);
		 when(mock.toString()).thenReturn("My toString");

		 // When
		 final StringBuilder actualStringBuilder = new SystemClassUser().newStringBuilder();
		 final String actualToString = actualStringBuilder.toString();


		 // Then
		 assertSame(mock, actualStringBuilder);
		 assertEquals("My toString", actualToString);
    }

    @Test(expected = IllegalStateException.class)
    public void triggerMockedCallFromInterfaceTypeInsteadOfConcreteType() throws Exception
    {
    	StringBuilder builder = mock(StringBuilder.class);
        when(builder.length()).then(new Answer<StringBuilder>(){
            public StringBuilder answer(InvocationOnMock invocation) throws Throwable{
                throw new IllegalStateException("Can't really happen");
            }
        });
        new SystemClassUser().lengthOf(builder);
    }
}