How to test Classes with @ConfigurationProperties and @Autowired

Question

I want to test small parts of the application that rely on properties loaded with @Autowired and @ConfigurationProperties. I am looking for a solut

Answer 1

If you use Spring Boot, now you only need:

@RunWith(SpringRunner.class)
@SpringBootTest

No extra @ContextConfiguration, no extra class only for tests to EnableAutoConfiguration and EnableConfigurationProperties. You don't have to specify the configuration class to load, they will all be loaded.

But, ensure the properties entries you want to read in main/resources/application.yml is also present in test/resources/application.yml. Repetition is unavoidable.

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Another way is:

1. Define a class of configuration only for tests, along with MyApplicationTest.java, at the same level. This class can be empty.

Like:

@EnableAutoConfiguration
@EnableConfigurationProperties(value = {
        ConnectionPoolConfig.class
})
public class MyApplicationTestConfiguration {
}

2. And, in the class to load the autowired configuration.

Like:

@RunWith(SpringRunner.class)
//@SpringBootTest // the first, easy way
@ContextConfiguration(classes = MyApplicationTestConfiguration.class,
        initializers = ConfigFileApplicationContextInitializer.class)
public class ConnectionPoolConfigTest {

    @Autowired
    private ConnectionPoolConfig config;

Basically, you:

• use a specific configuration to @EnableConfigurationProperties and @EnableAutoConfiguration, listing all the @ConfigurationProperties files you want to load
• in the test class, you load this configuration file of tests, with an initializer class defined by Spring to load application.yml file.

And, put the values to load in test/resources/application.yml. Repetition is unavoidable. If you need load another file, use @TestProperties() with a location. Note: @TestProperties only supports .properties files.

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Both way works for configuration class loading values

• either from application.yml/application.properties
• or from another properties file, specified by PropertySource, like @PropertySource(value = "classpath:threadpool.properties")

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Important

Last notes from Spring doc, as per here

Some people use Project Lombok to add getters and setters automatically. Make sure that Lombok does not generate any particular constructor for such a type, as it is used automatically by the container to instantiate the object.

Finally, only standard Java Bean properties are considered and binding on static properties is not supported.

That means, if you have lombok.@Builder without @NoArgsConstructor nor @AllArgsConstructor, properties injection will not happen because it only sees the invisible constructor created by @Builder. So, be sure to use none, or all of these annotations!