Using junit test to pass command line argument to Spring Boot application

Question

I have a very basic Spring Boot application, which is expecting an argument from command line, and without it doesn\'t work. Here is the code.

@SpringBootApplica         


        

Answer 1

I'm affraid that your solution will not work in a way that you presented (until you implement your own test framework for Spring).

This is because when you are running tests, Spring (its test SpringBootContextLoader to be more specific) runs your application in its own way. It instantiates SpringApplication and invokes its run method without any arguments. It also never uses your main method implemented in application.

However, you could refactor your application in a way that it'll be possible to test it.

I think (since you are using Spring) the easiest solution could be implemented using spring configuration properties instead of pure command line arguments. (But you should be aware that this solution should be used rather for "configuration arguments", because that's the main purpose of springs configuration properties mechanism)

Reading parameters using @Value annotation:

@SpringBootApplication
public class Application implements CommandLineRunner {

    @Value("${myCustomArgs.customArg1}")
    private String customArg1;

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    public void run(String... args) throws Exception {

        Assert.notNull(customArg1);
        //...
    }
}

Sample test:

@RunWith(SpringRunner.class)
@SpringBootTest({"myCustomArgs.customArg1=testValue"})
public class CityApplicationTests {

    @Test
    public void contextLoads() {
    }
}

And when running your command line app just add your custom params:

--myCustomArgs.customArg1=testValue