@InjectMocks Annotation in Mockito with Example

In this post, We will learn about @InjectMocks Annotation in Mockito with Example

Mockito’s @InjectMocks annotation usually allows us to inject mocked dependencies in the annotated class mocked object. This is very useful when we have an external dependency in the class want to mock. We can specify the mock objects to be injected using @Mock annotation.

Let’s try to understand the above concept using a demo project

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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.kkjavatutorials</groupId>
  <artifactId>MockitoInjectMocksAnnotationExample</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  
  	<properties>
		<maven.compiler.target>8</maven.compiler.target>
		<maven.compiler.source>8</maven.compiler.source>
	</properties>

	<dependencies>
		<dependency>
			<groupId>mysql</groupId>
			<artifactId>mysql-connector-java</artifactId>
			<version>8.0.21</version>
		</dependency>

		<dependency>
			<groupId>org.mockito</groupId>
			<artifactId>mockito-junit-jupiter</artifactId>
			<version>3.5.7</version>
			<scope>test</scope>
		</dependency>

	</dependencies>
  
</project>

<groupId>com.kkjavatutorials</groupId>

<artifactId>MockitoInjectMocksAnnotationExample</artifactId>

<version>0.0.1-SNAPSHOT</version>

<maven.compiler.target>8</maven.compiler.target>

<maven.compiler.source>8</maven.compiler.source>

</properties>

<groupId>mysql</groupId>

<artifactId>mysql-connector-java</artifactId>

</dependency>

<groupId>org.mockito</groupId>

<artifactId>mockito-junit-jupiter</artifactId>

</dependency>

</dependencies>

</project>

Resource interface and class

Dictionary.java

package com.kkjavatutorials;

public interface Dictionary {

	public abstract void add(String word, String meaning);
	public abstract String getMeaning(String word);
}

package com.kkjavatutorials;

public interface Dictionary {

public abstract void add(String word, String meaning);

public abstract String getMeaning(String word);

}

WordDictionary.java

package com.kkjavatutorials;

import java.util.HashMap;
import java.util.Map;

public class WordDictionary implements Dictionary {
	
    private Map<String, String> wordsMap;
 
    public WordDictionary() {
        wordsMap = new HashMap<String, String>();
    }
    public void add(String word, String meaning) {
        wordsMap.put(word, meaning);
    }
    public String getMeaning(String word) {
        return wordsMap.get(word);
    }
}

package com.kkjavatutorials;

import java.util.HashMap;

import java.util.Map;

public class WordDictionary implements Dictionary {

private Map<String, String> wordsMap;

public WordDictionary() {

wordsMap = new HashMap<String, String>();

}

public void add(String word, String meaning) {

wordsMap.put(word, meaning);

}

public String getMeaning(String word) {

return wordsMap.get(word);

}

Test class InjectMocksTest.java

package com.kkjavatutorials;
import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.Map;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import static org.mockito.Mockito.when;
import org.mockito.junit.jupiter.MockitoExtension;

@ExtendWith(value = { MockitoExtension.class })
public class InjectMocksTest {

	@Mock
	private Map<String, String> wordMap;

	@InjectMocks
	private Dictionary wordDictionary = new WordDictionary();

	@Test
	public void injectMocksTest() {
		
		when(wordMap.get("awesome")).thenReturn("Very Good");

		assertEquals("Very Good", wordDictionary.getMeaning("awesome"));
	}
}

package com.kkjavatutorials;

import static org.junit.jupiter.api.Assertions.assertEquals;

import java.util.Map;

import org.junit.jupiter.api.Test;

import org.junit.jupiter.api.extension.ExtendWith;

import org.mockito.InjectMocks;

import org.mockito.Mock;

import static org.mockito.Mockito.when;

import org.mockito.junit.jupiter.MockitoExtension;

@ExtendWith(value = { MockitoExtension.class })

public class InjectMocksTest {

@Mock

private Map<String, String> wordMap;

@InjectMocks

private Dictionary wordDictionary = new WordDictionary();

@Test

public void injectMocksTest() {

when(wordMap.get("awesome")).thenReturn("Very Good");

assertEquals("Very Good", wordDictionary.getMeaning("awesome"));

}

The Output of the above project:

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Mockito and JUnit Integration Using Maven Example
@Mock and @Spy Mockito Annotations With Example
Mockito – Verifying Method Calls
@Captor Annotation in Mockito with Example
Adding behavior to mocked object in Mockito
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That’s all about @InjectMocks Annotation in Mockito with Example
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