![\"Write](\"https:\/\/huongdanjava.com\/wp-content\/uploads\/2020\/02\/write-unit-test-for-spring-boot-application-1.png\")
<\/p>\nWhen working with applications that use Spring Boot, you will need to write Unit Test for your code. In this tutorial, I will show you how to write Unit Test for the Spring Boot application!<\/p>\n
First, I will create a simple Spring Boot application for example:<\/p>\n
<\/p>\n
This application just does a simple job of printing a message to the console with the content “Hello Khanh. Total of 2 and 3 is 5”. To do this, our application will have 2 classes declared in the Spring container with the following content:<\/p>\n
Hello class:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.springframework.stereotype.Component;\r\n\r\n@Component\r\npublic class Hello {\r\n\r\n public String say(String name) {\r\n return \"Hello \" + name;\r\n }\r\n}\r\n<\/pre>\nThis class defines a method that allows us to pass a name and it will return the string “Hello” plus the name you passed.<\/p>\n
Calculation class:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.springframework.stereotype.Service;\r\n\r\n@Service\r\npublic class Calculation {\r\n\r\n public int sum(int a, int b) {\r\n return a + b;\r\n }\r\n}\r\n<\/pre>\nThis class allows us to calculate the sum of 2 numbers.<\/p>\n
The result when running this program will be as follows:<\/p>\n
![\"Write](\"https:\/\/huongdanjava.com\/wp-content\/uploads\/2020\/02\/write-unit-test-for-spring-boot-application-2.png\")
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Ok, now we will proceed to write Unit Test code for this application!<\/p>\n
The idea is that we need to write Unit Tests to test when the application runs, the two beans of Hello and Calculation classes must be initialized in the Spring container and their methods must return the values we want.<\/p>\n
To do this, first you need to make sure the dependency of the Spring Boot Test is declared in your pom.xml file. When I created the Spring Boot project using the Spring Tool Suite, it was included as follows:<\/p>\n
<dependency>\r\n <groupId>org.springframework.boot<\/groupId>\r\n <artifactId>spring-boot-starter-test<\/artifactId>\r\n <scope>test<\/scope>\r\n<\/dependency>\r\n<\/pre>\n<\/pre>\nTo write a Unit Test for the Spring Boot application, you just need to declare in the Test class an annotation of Spring Boot Test @SpringBootTest<\/strong>. For example:<\/p>\npackage com.huongdanjava.springboot;\r\n\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\n\r\n@SpringBootTest\r\npublic class HelloTest {\r\n\r\n}\r\n<\/pre>\nOr:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\n\r\n@SpringBootTest\r\npublic class CalculationTest {\r\n\r\n}\r\n<\/pre>\nThe SpringBootUnitTestApplicationTests class has been automatically added:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.junit.jupiter.api.Test;\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\n\r\n@SpringBootTest\r\nclass SpringBootUnitTestApplicationTests {\r\n\r\n @Test\r\n void contextLoads() {\r\n }\r\n\r\n}\r\n<\/pre>\nWith this @SpringBootTest annotation, the Spring Boot Test will automatically run a Spring container and initialize beans in this Spring container while we run the test.<\/p>\n
Bean of which class will be initialized in Spring container, depending on our configuration.<\/p>\n
If you declare the @ContextConfiguration annotation with value as classes containing bean information definition, only the beans defined in these classes will be initialized.<\/p>\n
If you do not declare the @ContextConfiguration annotation, the Spring Boot Test will automatically scan for classes that are declared with the @Configuration annotation and used with the @SpringBootConfiguration annotation to initialize the bean.<\/p>\n
In my example, I am using auto component scan to initialize beans in Spring, do not explicitly declare beans, so these beans are used with the @SpringBootConfiguration annotation to initialize.<\/p>\n
You can add code tests to test the beans of classes Hello and Calculation must be initialized in SpringBootUnitTestApplicationTests class as follows:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.junit.jupiter.api.Assertions;\r\nimport org.junit.jupiter.api.Test;\r\nimport org.springframework.beans.factory.annotation.Autowired;\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\nimport org.springframework.context.ApplicationContext;\r\n\r\n@SpringBootTest\r\nclass SpringBootUnitTestApplicationTests {\r\n\r\n @Autowired\r\n private ApplicationContext context;\r\n\r\n @Test\r\n public void testCalculation() {\r\n Assertions.assertTrue(context.getBean(Calculation.class) != null);\r\n }\r\n\r\n @Test\r\n public void testHello() {\r\n Assertions.assertTrue(context.getBean(Hello.class) != null);\r\n }\r\n\r\n}\r\n<\/pre>\nTest for Hello and Calculation classes will be as follows:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.junit.jupiter.api.Assertions;\r\nimport org.junit.jupiter.api.Test;\r\nimport org.springframework.beans.factory.annotation.Autowired;\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\nimport org.springframework.context.ApplicationContext;\r\n\r\n@SpringBootTest\r\npublic class CalculationTest {\r\n\r\n @Autowired\r\n private ApplicationContext context;\r\n\r\n @Test\r\n public void testSum() {\r\n Calculation calculation = context.getBean(Calculation.class);\r\n\r\n Assertions.assertEquals(9, calculation.sum(4, 5));\r\n }\r\n}\r\n<\/pre>\npackage com.huongdanjava.springboot;\r\n\r\nimport org.junit.jupiter.api.Assertions;\r\nimport org.junit.jupiter.api.Test;\r\nimport org.springframework.beans.factory.annotation.Autowired;\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\nimport org.springframework.context.ApplicationContext;\r\n\r\n@SpringBootTest\r\npublic class HelloTest {\r\n\r\n @Autowired\r\n private ApplicationContext context;\r\n\r\n @Test\r\n public void testSay() {\r\n Hello hello = context.getBean(Hello.class);\r\n\r\n Assertions.assertEquals(\"Hello Khanh\", hello.say(\"Khanh\"));\r\n }\r\n}\r\n<\/pre>\nIf you only want to test the Hello class, you can create a new TestConfiguration class with the following content:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.springframework.context.annotation.Bean;\r\nimport org.springframework.context.annotation.Configuration;\r\n\r\n@Configuration\r\npublic class TestConfiguration {\r\n\r\n @Bean\r\n public Hello hello() {\r\n return new Hello();\r\n }\r\n}\r\n<\/pre>\nThen use the @ContextConfiguration annotation to declare this TestConfiguration class in to write tests:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.junit.jupiter.api.Assertions;\r\nimport org.junit.jupiter.api.Test;\r\nimport org.springframework.beans.factory.annotation.Autowired;\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\nimport org.springframework.context.ApplicationContext;\r\nimport org.springframework.test.context.ContextConfiguration;\r\n\r\n@SpringBootTest\r\n@ContextConfiguration(classes = { TestConfiguration.class })\r\npublic class Hello1Test {\r\n\r\n @Autowired\r\n private ApplicationContext context;\r\n\r\n @Test\r\n public void testSay() {\r\n Hello hello = context.getBean(Hello.class);\r\n\r\n Assertions.assertEquals(\"Hello Khanh\", hello.say(\"Khanh\"));\r\n }\r\n\r\n}\r\n<\/pre>\nIn this case, you won’t be able to get the bean of the Calculation class. For example:<\/p>\n
package com.huongdanjava.springboot;\r\n\r\nimport org.junit.jupiter.api.Assertions;\r\nimport org.junit.jupiter.api.Test;\r\nimport org.springframework.beans.factory.annotation.Autowired;\r\nimport org.springframework.boot.test.context.SpringBootTest;\r\nimport org.springframework.context.ApplicationContext;\r\nimport org.springframework.test.context.ContextConfiguration;\r\n\r\n@SpringBootTest\r\n@ContextConfiguration(classes = { TestConfiguration.class })\r\npublic class Hello1Test {\r\n\r\n @Autowired\r\n private ApplicationContext context;\r\n\r\n @Test\r\n public void testSay() {\r\n Hello hello = context.getBean(Hello.class);\r\n\r\n Assertions.assertEquals(\"Hello Khanh\", hello.say(\"Khanh\"));\r\n }\r\n\r\n @Test\r\n public void testBeanConfiguration() {\r\n Calculation calculation = context.getBean(Calculation.class);\r\n }\r\n}\r\n<\/pre>\nThe error will happen immediately:<\/p>\n
![\"Write](\"https:\/\/huongdanjava.com\/wp-content\/uploads\/2020\/02\/write-unit-test-for-spring-boot-application-3.png\")
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