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What You Will Learn during this Step:

  • How to capture an argument which is passed to a mock?

Useful Snippets and References

First Snippet

@Test
    public void captureArgument() {
        ArgumentCaptor<String> argumentCaptor = ArgumentCaptor.forClass(String.class);

        TodoService todoService = mock(TodoService.class);

        List<String> allTodos = Arrays.asList("Learn Spring MVC", "Learn Spring", "Learn to Dance");
        Mockito.when(todoService.retrieveTodos("Ranga")).thenReturn(allTodos);

        TodoBusinessImpl todoBusinessImpl = new TodoBusinessImpl(todoService);
        todoBusinessImpl.deleteTodosNotRelatedToSpring("Ranga");
        Mockito.verify(todoService).deleteTodo(argumentCaptor.capture());

        assertEquals("Learn to Dance", argumentCaptor.getValue());
    }

Files List

/pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.in28minutes.mockito</groupId>
	<artifactId>mockito-tutorial</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.mockito</groupId>
			<artifactId>mockito-all</artifactId>
			<version>1.10.19</version>
			<scope>test</scope>
		</dependency>
	</dependencies>
</project>

/src/main/java/com/in28minutes/business/TodoBusinessImpl.java

package com.in28minutes.business;

import java.util.ArrayList;
import java.util.List;

import com.in28minutes.data.api.TodoService;

public class TodoBusinessImpl {
	private TodoService todoService;

	TodoBusinessImpl(TodoService todoService) {
		this.todoService = todoService;
	}

	public List<String> retrieveTodosRelatedToSpring(String user) {
		List<String> filteredTodos = new ArrayList<String>();
		List<String> allTodos = todoService.retrieveTodos(user);
		for (String todo : allTodos) {
			if (todo.contains("Spring")) {
				filteredTodos.add(todo);
			}
		}
		return filteredTodos;
	}

	public void deleteTodosNotRelatedToSpring(String user) {
		List<String> allTodos = todoService.retrieveTodos(user);
		for (String todo : allTodos) {
			if (!todo.contains("Spring")) {
				todoService.deleteTodo(todo);
			}
		}
	}
}

/src/main/java/com/in28minutes/data/api/TodoService.java

package com.in28minutes.data.api;

import java.util.List;

// External Service - Lets say this comes from WunderList
public interface TodoService {

	public List<String> retrieveTodos(String user);

	void deleteTodo(String todo);

}

/src/test/java/com/in28minutes/business/TodoBusinessImplMockitoTest.java

package com.in28minutes.business;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertThat;
import static org.mockito.BDDMockito.given;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

import java.util.Arrays;
import java.util.List;

import org.junit.Test;
import org.mockito.ArgumentCaptor;
import org.mockito.Mockito;

import com.in28minutes.data.api.TodoService;

public class TodoBusinessImplMockitoTest {

	@Test
	public void usingMockito() {
		TodoService todoService = mock(TodoService.class);
		List<String> allTodos = Arrays.asList("Learn Spring MVC",
				"Learn Spring", "Learn to Dance");
		when(todoService.retrieveTodos("Ranga")).thenReturn(allTodos);
		TodoBusinessImpl todoBusinessImpl = new TodoBusinessImpl(todoService);
		List<String> todos = todoBusinessImpl
				.retrieveTodosRelatedToSpring("Ranga");
		assertEquals(2, todos.size());
	}

	@Test
	public void usingMockito_UsingBDD() {
		TodoService todoService = mock(TodoService.class);
		TodoBusinessImpl todoBusinessImpl = new TodoBusinessImpl(todoService);
		List<String> allTodos = Arrays.asList("Learn Spring MVC",
				"Learn Spring", "Learn to Dance");

		//given
		given(todoService.retrieveTodos("Ranga")).willReturn(allTodos);

		//when
		List<String> todos = todoBusinessImpl
				.retrieveTodosRelatedToSpring("Ranga");

		//then
		assertThat(todos.size(), is(2));
	}

	@Test
	public void letsTestDeleteNow() {

		TodoService todoService = mock(TodoService.class);

		List<String> allTodos = Arrays.asList("Learn Spring MVC",
				"Learn Spring", "Learn to Dance");

		when(todoService.retrieveTodos("Ranga")).thenReturn(allTodos);

		TodoBusinessImpl todoBusinessImpl = new TodoBusinessImpl(todoService);

		todoBusinessImpl.deleteTodosNotRelatedToSpring("Ranga");

		verify(todoService).deleteTodo("Learn to Dance");

		verify(todoService, Mockito.never()).deleteTodo("Learn Spring MVC");

		verify(todoService, Mockito.never()).deleteTodo("Learn Spring");

		verify(todoService, Mockito.times(1)).deleteTodo("Learn to Dance");
		// atLeastOnce, atLeast

	}

	@Test
	public void captureArgument() {
		ArgumentCaptor<String> argumentCaptor = ArgumentCaptor
				.forClass(String.class);

		TodoService todoService = mock(TodoService.class);

		List<String> allTodos = Arrays.asList("Learn Spring MVC",
				"Learn Spring", "Learn to Dance");
		Mockito.when(todoService.retrieveTodos("Ranga")).thenReturn(allTodos);

		TodoBusinessImpl todoBusinessImpl = new TodoBusinessImpl(todoService);
		todoBusinessImpl.deleteTodosNotRelatedToSpring("Ranga");
		Mockito.verify(todoService).deleteTodo(argumentCaptor.capture());

		assertEquals("Learn to Dance", argumentCaptor.getValue());
	}
}

/src/test/java/com/in28minutes/business/TodoBusinessImplStubTest.java

package com.in28minutes.business;

import static org.junit.Assert.assertEquals;

import java.util.List;

import org.junit.Test;

import com.in28minutes.data.api.TodoService;
import com.in28minutes.data.stub.TodoServiceStub;

public class TodoBusinessImplStubTest {

	@Test
	public void usingAStub() {
		TodoService todoService = new TodoServiceStub();
		TodoBusinessImpl todoBusinessImpl = new TodoBusinessImpl(todoService);
		List<String> todos = todoBusinessImpl
				.retrieveTodosRelatedToSpring("Ranga");
		assertEquals(2, todos.size());
	}
}

/src/test/java/com/in28minutes/data/stub/TodoServiceStub.java

package com.in28minutes.data.stub;

import java.util.Arrays;
import java.util.List;

import com.in28minutes.data.api.TodoService;

public class TodoServiceStub implements TodoService {
	public List<String> retrieveTodos(String user) {
		return Arrays.asList("Learn Spring MVC", "Learn Spring",
				"Learn to Dance");
	}

	public void deleteTodo(String todo) {

	}
}

/src/test/java/com/in28minutes/mockito/FirstMockitoTest.java

package com.in28minutes.mockito;

import static org.junit.Assert.assertTrue;

import org.junit.Test;

public class FirstMockitoTest {

	@Test
	public void test() {
		assertTrue(true);
	}

}

/src/test/java/com/in28minutes/mockito/ListTest.java

package com.in28minutes.mockito;

import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNull;
import static org.junit.Assert.assertThat;
import static org.mockito.BDDMockito.given;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

import java.util.List;

import org.junit.Test;
import org.mockito.Mockito;

public class ListTest {

	@Test
	public void letsMockListSize() {
		List list = mock(List.class);
		when(list.size()).thenReturn(10);
		assertEquals(10, list.size());
	}

	@Test
	public void letsMockListSizeWithMultipleReturnValues() {
		List list = mock(List.class);
		when(list.size()).thenReturn(10).thenReturn(20);
		assertEquals(10, list.size()); // First Call
		assertEquals(20, list.size()); // Second Call
	}

	@Test
	public void letsMockListGet() {
		List<String> list = mock(List.class);
		when(list.get(0)).thenReturn("in28Minutes");
		assertEquals("in28Minutes", list.get(0));
		assertNull(list.get(1));
	}

	@Test(expected = RuntimeException.class)
	public void letsMockListGetToThrowException() {
		List<String> list = mock(List.class);
		when(list.get(Mockito.anyInt())).thenThrow(
				new RuntimeException("Something went wrong"));
		list.get(0);
	}

	@Test
	public void letsMockListGetWithAny() {
		List<String> list = mock(List.class);
		Mockito.when(list.get(Mockito.anyInt())).thenReturn("in28Minutes");
		// If you are using argument matchers, all arguments
		// have to be provided by matchers.
		assertEquals("in28Minutes", list.get(0));
		assertEquals("in28Minutes", list.get(1));
	}

	@Test
	public void bddAliases_UsingGivenWillReturn() {
		List<String> list = mock(List.class);

		//given
		given(list.get(Mockito.anyInt())).willReturn("in28Minutes");

		//then
		assertThat("in28Minutes", is(list.get(0)));
		assertThat("in28Minutes", is(list.get(0)));
	}
}