Spring Boot ConfigurationProperties fail to initialize for integration testing - gradle

Question

Using gradle (3.4.1) with an integrationTest configuration, the tests using the ConfigurationProperties of Spring Boot (1.5.1.RELEASE) is failing to initialize even though the application initializes correctly (./gradlew bootRun). The class annotated with ConfigurationProperties is similar to the following
#Component
#ConfigurationProperties(prefix = "foo")
#Validated
public class AppConfiguration {
#NonNull
private URL serviceUrl;
...
The configuration file does have getters and setters. The error that is generated is similar to the following
java.lang.IllegalStateException: Failed to load ApplicationContext
....
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'AppConfiguration': Could not bind properties to AppConfiguration
....
Caused by: org.springframework.validation.BindException: org.springframework.boot.bind.RelaxedDataBinder$RelaxedBeanPropertyBindingResult
Field error in object 'foo' on field 'serviceUrl': rejected value [null]; codes ...
The configuration class of the integration test is annotated as follows
#Configuration
#ComponentScan(...)
#EnableConfigurationProperties
#EnableIntegration
public static class ContextConfiguration {}

Answer 1

The test class had the following annotations
#RunWith(SpringJUnit4ClassRunner.class)
#ContextConfiguration
public class ReleaseTest {
...
After looking at the Spring Boot code for the ConfigurationPropertiesBindingPostProcessor#postProcessBeforeInitialization() it suggested that the property source was not being discovered. Adding the org.springframework.boot:spring-boot-starter-test artifact as a compile-time dependency and modifying the context configuration of the test class to
#ContextConfiguration(initializers = ConfigFileApplicationContextInitializer.class)
the AppConfiguration class was initialized properly using a YAML-based properties file.
An alternative is to add
#TestPropertySource("classpath:/application.properties")
This approach doesn't require the spring-boot-starter-test dependency and requires that a "traditional" properties file is used (a YAML file will not work with this approach).