Populating Spring @Value during Unit Test

Question

I'm trying to write a Unit Test for a simple bean that's used in my program to validate forms. The bean is annotated with @Component and has a class variable that is initialized using

@Value("${this.property.value}") private String thisProperty; 

I would like to write unit tests for the validation methods inside this class, however, if possible I would like to do so without utilizing the properties file. My reasoning behind this, is that if the value I'm pulling from the properties file changes, I would like that to not affect my test case. My test case is testing the code that validates the value, not the value itself.

Is there a way to use Java code inside my test class to initialize a Java class and populate the Spring @Value property inside that class then use that to test with?

I did find this How To that seems to be close, but still uses a properties file. I would rather it all be Java code.

Answer 1

If possible I would try to write those test without Spring Context. If you create this class in your test without spring, then you have full control over its fields.

To set the @value field you can use Springs ReflectionTestUtils - it has a method setField to set private fields.

@see JavaDoc: ReflectionTestUtils.setField(java.lang.Object, java.lang.String, java.lang.Object)

Answer 2

Since Spring 4.1 you could set up property values just in code by using org.springframework.test.context.TestPropertySource annotation on Unit Tests class level. You could use this approach even for injecting properties into dependent bean instances

For example

@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(classes = FooTest.Config.class) @TestPropertySource(properties = {     "some.bar.value=testValue", }) public class FooTest {    @Value("${some.bar.value}")   String bar;    @Test   public void testValueSetup() {     assertEquals("testValue", bar);   }     @Configuration   static class Config {      @Bean     public static PropertySourcesPlaceholderConfigurer propertiesResolver() {         return new PropertySourcesPlaceholderConfigurer();     }    }  } 

Note: It's necessary to have instance of org.springframework.context.support.PropertySourcesPlaceholderConfigurer in Spring context

Edit 24-08-2017: If you are using SpringBoot 1.4.0 and later you could initialize tests with @SpringBootTest and @SpringBootConfiguration annotations. More info here

In case of SpringBoot we have following code

@SpringBootTest @SpringBootConfiguration @RunWith(SpringJUnit4ClassRunner.class) @TestPropertySource(properties = {     "some.bar.value=testValue", }) public class FooTest {    @Value("${some.bar.value}")   String bar;    @Test   public void testValueSetup() {     assertEquals("testValue", bar);   }  }