Context Configuration with Dynamic Property Sources

As of TODAY Framework 5.2.5, the TestContext framework provides support for dynamic properties via the @DynamicPropertySource annotation. This annotation can be used in integration tests that need to add properties with dynamic values to the set of PropertySources in the Environment for the ApplicationContext loaded for the integration test.

The @DynamicPropertySource annotation and its supporting infrastructure were originally designed to allow properties from Testcontainers based tests to be exposed easily to Infra integration tests. However, this feature may also be used with any form of external resource whose lifecycle is maintained outside the test’s ApplicationContext.

In contrast to the @TestPropertySource annotation that is applied at the class level, @DynamicPropertySource must be applied to a static method that accepts a single DynamicPropertyRegistry argument which is used to add name-value pairs to the Environment. Values are dynamic and provided via a Supplier which is only invoked when the property is resolved. Typically, method references are used to supply values, as can be seen in the following example which uses the Testcontainers project to manage a Redis container outside of the Infra ApplicationContext. The IP address and port of the managed Redis container are made available to components within the test’s ApplicationContext via the redis.host and redis.port properties. These properties can be accessed via Infra Environment abstraction or injected directly into Infra-managed components – for example, via @Value("${redis.host}") and @Value("${redis.port}"), respectively.

If you use @DynamicPropertySource in a base class and discover that tests in subclasses fail because the dynamic properties change between subclasses, you may need to annotate your base class with @DirtiesContext to ensure that each subclass gets its own ApplicationContext with the correct dynamic properties.

 
@JUnitConfig(/* ... */)
@Testcontainers
class ExampleIntegrationTests {

  @Container
  static GenericContainer redis =
    new GenericContainer("redis:5.0.3-alpine").withExposedPorts(6379);

  @DynamicPropertySource
  static void redisProperties(DynamicPropertyRegistry registry) {
    registry.add("redis.host", redis::getHost);
    registry.add("redis.port", redis::getFirstMappedPort);
  }

  // tests ...

}

Precedence

Dynamic properties have higher precedence than those loaded from @TestPropertySource, the operating system’s environment, Java system properties, or property sources added by the application declaratively by using @PropertySource or programmatically. Thus, dynamic properties can be used to selectively override properties loaded via @TestPropertySource, system property sources, and application property sources.