Document precedence for @DynamicPropertySource

Closes gh-24837

spring-test/src/main/java/org/springframework/test/context/DynamicPropertySource.java

@@ -41,8 +41,17 @@ import java.lang.annotation.Target;
  * is resolved. Typically, method references are used to supply values, as in the
  * following example.
  *
- * <h3>Example</h3>
+ * <h3>Precedence</h3>
+ * <p>Dynamic properties have higher precedence than those loaded from
+ * {@link TestPropertySource @TestPropertySource}, the operating system's
+ * environment, Java system properties, or property sources added by the
+ * application declaratively by using
+ * {@link org.springframework.context.annotation.PropertySource @PropertySource}
+ * or programmatically. Thus, dynamic properties can be used to selectively
+ * override properties loaded via {@code @TestPropertySource}, system property
+ * sources, and application property sources.
  *
+ * <h3>Example</h3>
  * <pre class="code">
  * &#064;SpringJUnitConfig(...)
  * &#064;Testcontainers

spring-test/src/main/java/org/springframework/test/context/TestPropertySource.java

@@ -44,7 +44,9 @@ import org.springframework.core.annotation.AliasFor;
  * or some other means). Thus, test property sources can be used to selectively
  * override properties defined in system and application property sources.
  * Furthermore, inlined {@link #properties} have higher precedence than
- * properties loaded from resource {@link #locations}.
+ * properties loaded from resource {@link #locations}. Note, however, that
+ * properties registered via {@link DynamicPropertySource @DynamicPropertySource}
+ * have higher precedence than those loaded via {@code @TestPropertySource}.
  *
  * <h3>Default Properties File Detection</h3>
  * <p>If {@code @TestPropertySource} is declared as an <em>empty</em> annotation

spring-test/src/test/java/org/springframework/test/context/DynamicPropertySourceIntegrationTests.java

@@ -16,38 +16,71 @@
 
 package org.springframework.test.context;
 
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.beans.factory.annotation.Value;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
-import org.springframework.stereotype.Component;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.MutablePropertySources;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.TestInstance.Lifecycle.PER_CLASS;
 
 /**
- * Integration test for {@link DynamicPropertySource @DynamicPropertySource}.
+ * Integration tests for {@link DynamicPropertySource @DynamicPropertySource}.
  *
  * @author Phillip Webb
  * @author Sam Brannen
  */
 @SpringJUnitConfig
+@TestPropertySource(properties = "test.container.ip: test")
+@TestInstance(PER_CLASS)
+@DisplayName("@DynamicPropertySource integration tests")
 class DynamicPropertySourceIntegrationTests {
 
-	static DemoContainer container = new DemoContainer();
+	private static final String TEST_CONTAINER_IP = "test.container.ip";
 
+	static {
+		System.setProperty(TEST_CONTAINER_IP, "system");
+	}
+
+	static DemoContainer container = new DemoContainer();
 
 	@DynamicPropertySource
 	static void containerProperties(DynamicPropertyRegistry registry) {
-		registry.add("test.container.ip", container::getIpAddress);
+		registry.add(TEST_CONTAINER_IP, container::getIpAddress);
 		registry.add("test.container.port", container::getPort);
 	}
 
 
+	@AfterAll
+	void clearSystemProperty() {
+		System.clearProperty(TEST_CONTAINER_IP);
+	}
+
+	@Test
+	@DisplayName("@DynamicPropertySource overrides @TestPropertySource and JVM system property")
+	void dynamicPropertySourceOverridesTestPropertySourceAndSystemProperty(@Autowired ConfigurableEnvironment env) {
+		MutablePropertySources propertySources = env.getPropertySources();
+		assertThat(propertySources.size()).isGreaterThanOrEqualTo(4);
+		assertThat(propertySources.contains("Dynamic Test Properties")).isTrue();
+		assertThat(propertySources.contains("Inlined Test Properties")).isTrue();
+		assertThat(propertySources.contains("systemProperties")).isTrue();
+		assertThat(propertySources.get("Dynamic Test Properties").getProperty(TEST_CONTAINER_IP)).isEqualTo("127.0.0.1");
+		assertThat(propertySources.get("Inlined Test Properties").getProperty(TEST_CONTAINER_IP)).isEqualTo("test");
+		assertThat(propertySources.get("systemProperties").getProperty(TEST_CONTAINER_IP)).isEqualTo("system");
+		assertThat(env.getProperty(TEST_CONTAINER_IP)).isEqualTo("127.0.0.1");
+	}
+
 	@Test
-	void hasInjectedValues(@Autowired Service service) {
+	@DisplayName("@Service has values injected from @DynamicPropertySource")
+	void serviceHasInjectedValues(@Autowired Service service) {
 		assertThat(service.getIp()).isEqualTo("127.0.0.1");
 		assertThat(service.getPort()).isEqualTo(4242);
 	}
@@ -58,7 +91,6 @@ class DynamicPropertySourceIntegrationTests {
 	static class Config {
 	}
 
-	@Component
 	static class Service {
 
 		private final String ip;

src/docs/asciidoc/testing.adoc

@@ -411,6 +411,7 @@ Spring's testing annotations include the following:
 * <<spring-testing-annotation-contexthierarchy>>
 * <<spring-testing-annotation-activeprofiles>>
 * <<spring-testing-annotation-testpropertysource>>
+* <<spring-testing-annotation-dynamicpropertysource>>
 * <<spring-testing-annotation-dirtiescontext>>
 * <<spring-testing-annotation-testexecutionlisteners>>
 * <<spring-testing-annotation-commit>>
@@ -758,13 +759,6 @@ locations of properties files and inlined properties to be added to the set of
 `PropertySources` in the `Environment` for an `ApplicationContext` loaded for an
 integration test.
 
-Test property sources have higher precedence than those loaded from the operating
-system's environment or Java system properties as well as property sources added by the
-application declaratively through `@PropertySource` or programmatically. Thus, test
-property sources can be used to selectively override properties defined in system and
-application property sources. Furthermore, inlined properties have higher precedence than
-properties loaded from resource locations.
-
 The following example demonstrates how to declare a properties file from the classpath:
 
 [source,java,indent=0,subs="verbatim,quotes",role="primary"]
@@ -816,6 +810,65 @@ The following example demonstrates how to declare inlined properties:
 
 See <<testcontext-ctx-management-property-sources>> for examples and further details.
 
+[[spring-testing-annotation-dynamicpropertysource]]
+===== `@DynamicPropertySource`
+
+`@DynamicPropertySource` is a method-level annotation that you can use to register
+_dynamic_ properties to be added to the set of `PropertySources` in the `Environment` for
+an `ApplicationContext` loaded for an integration test. Dynamic properties are useful
+when you do not know the value of the properties upfront – for example, if the properties
+are managed by an external resource such as for a container managed by the
+https://www.testcontainers.org/[Testcontainers] project.
+
+The following example demonstrates how to register a dynamic property:
+
+[source,java,indent=0,subs="verbatim,quotes",role="primary"]
+.Java
+----
+	@ContextConfiguration
+	class MyIntegrationTests {
+
+		static MyExternalServer server = // ...
+
+		@DynamicPropertySource // <1>
+		static void dynamicProperties(DynamicPropertyRegistry registry) { // <2>
+			registry.add("server.port", server::getPort); // <3>
+		}
+
+		// tests ...
+	}
+----
+<1> Annotate a `static` method with `@DynamicPropertySource`.
+<2> Accept a `DynamicPropertyRegistry` as an argument.
+<3> Register a dynamic `server.port` property to be retrieved lazily from the server.
+
+[source,kotlin,indent=0,subs="verbatim,quotes",role="secondary"]
+.Kotlin
+----
+	@ContextConfiguration
+	class MyIntegrationTests {
+
+		companion object {
+
+			@JvmStatic
+			val server: MyExternalServer = // ...
+
+			@DynamicPropertySource // <1>
+			@JvmStatic
+			fun dynamicProperties(registry: DynamicPropertyRegistry) { // <2>
+				registry.add("server.port", server::getPort) // <3>
+			}
+		}
+
+		// tests ...
+	}
+----
+<1> Annotate a `static` method with `@DynamicPropertySource`.
+<2> Accept a `DynamicPropertyRegistry` as an argument.
+<3> Register a dynamic `server.port` property to be retrieved lazily from the server.
+
+See <<testcontext-ctx-management-dynamic-property-sources>> for further details.
+
 [[spring-testing-annotation-dirtiescontext]]
 ===== `@DirtiesContext`
 
@@ -3835,12 +3888,14 @@ file is `classpath:com/example/MyTest.properties`. If the default cannot be dete
 
 ====== Precedence
 
-Test property sources have higher precedence than those loaded from the operating
-system's environment, Java system properties, or property sources added by the
-application declaratively by using `@PropertySource` or programmatically. Thus, test
-property sources can be used to selectively override properties defined in system and
-application property sources. Furthermore, inlined properties have higher precedence than
-properties loaded from resource locations.
+Test properties have higher precedence than those defined in the operating system's
+environment, Java system properties, or property sources added by the application
+declaratively by using `@PropertySource` or programmatically. Thus, test properties can
+be used to selectively override properties loaded from system and application property
+sources. Furthermore, inlined properties have higher precedence than properties loaded
+from resource locations. Note, however, that properties registered via
+<<testcontext-ctx-management-dynamic-property-sources, `@DynamicPropertySource`>> have
+higher precedence than those loaded via `@TestPropertySource`.
 
 In the next example, the `timezone` and `port` properties and any properties defined in
 `"/test.properties"` override any properties of the same name that are defined in system
@@ -3968,8 +4023,8 @@ to define properties in both a subclass and its superclass by using inline prope
 ===== Context Configuration with Dynamic Property Sources
 
 As of Spring Framework 5.2.5, the TestContext framework provides support for _dynamic_
-property sources via the `@DynamicPropertySource` annotation. This annotation can be used
-in integration tests that need to add properties with dynamic values to the set of
+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.
 
@@ -3988,8 +4043,9 @@ references are used to supply values, as can be seen in the following example wh
 the Testcontainers project to manage a Redis container outside of the Spring
 `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 injected into Spring-managed components
-via `@Value("${redis.host}")` and `@Value("${redis.port}")`, respectively.
+`redis.port` properties. These properties can be accessed via Spring's `Environment`
+abstraction or injected directly into Spring-managed components – for example, via
+`@Value("${redis.host}")` and `@Value("${redis.port}")`, respectively.
 
 [source,java,indent=0,subs="verbatim,quotes",role="primary"]
 .Java
@@ -4037,6 +4093,14 @@ via `@Value("${redis.host}")` and `@Value("${redis.port}")`, respectively.
 	}
 ----
 
+====== 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.
+
 [[testcontext-ctx-management-web]]
 ===== Loading a `WebApplicationContext`
 
@@ -4272,7 +4336,9 @@ framework uses the following configuration parameters to build the context cache
 * `locations` (from `@ContextConfiguration`)
 * `classes` (from `@ContextConfiguration`)
 * `contextInitializerClasses` (from `@ContextConfiguration`)
-* `contextCustomizers` (from `ContextCustomizerFactory`)
+* `contextCustomizers` (from `ContextCustomizerFactory`) – this includes
+  `@DynamicPropertySource` methods as well as various features from Spring Boot's
+  testing support such as `@MockBean` and `@SpyBean`.
 * `contextLoader` (from `@ContextConfiguration`)
 * `parent` (from `@ContextHierarchy`)
 * `activeProfiles` (from `@ActiveProfiles`)