Allow ApplicationContextRunner to return non-refreshed context

Add `AbstractApplicationContextRunner.prepare` which can be used to
test an `ApplicationContext` that has been prepared but not refreshed.

Closes gh-31302

spring-boot-project/spring-boot-test/src/main/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunner.java

@@ -337,16 +337,32 @@ public abstract class AbstractApplicationContextRunner<SELF extends AbstractAppl
 	 */
 	@SuppressWarnings("unchecked")
 	public SELF run(ContextConsumer<? super A> consumer) {
-		withContextClassLoader(this.runnerConfiguration.classLoader,
-				() -> this.runnerConfiguration.systemProperties.applyToSystemProperties(() -> {
-					try (A context = createAssertableContext()) {
-						accept(consumer, context);
-					}
-					return null;
-				}));
+		withContextClassLoader(this.runnerConfiguration.classLoader, () -> this.runnerConfiguration.systemProperties
+				.applyToSystemProperties(() -> consumeAssertableContext(true, consumer)));
 		return (SELF) this;
 	}
 
+	/**
+	 * Prepare a new {@link ApplicationContext} based on the current state of this loader.
+	 * The context is consumed by the specified {@code consumer} and closed upon
+	 * completion. Unlike {@link #run(ContextConsumer)}, this method does not refresh the
+	 * consumed context.
+	 * @param consumer the consumer of the created {@link ApplicationContext}
+	 * @return this instance
+	 */
+	@SuppressWarnings("unchecked")
+	public SELF prepare(ContextConsumer<? super A> consumer) {
+		withContextClassLoader(this.runnerConfiguration.classLoader, () -> this.runnerConfiguration.systemProperties
+				.applyToSystemProperties(() -> consumeAssertableContext(false, consumer)));
+		return (SELF) this;
+	}
+
+	private void consumeAssertableContext(boolean refresh, ContextConsumer<? super A> consumer) {
+		try (A context = createAssertableContext(refresh)) {
+			accept(consumer, context);
+		}
+	}
+
 	private void withContextClassLoader(ClassLoader classLoader, Runnable action) {
 		if (classLoader == null) {
 			action.run();
@@ -365,14 +381,14 @@ public abstract class AbstractApplicationContextRunner<SELF extends AbstractAppl
 	}
 
 	@SuppressWarnings("unchecked")
-	private A createAssertableContext() {
+	private A createAssertableContext(boolean refresh) {
 		ResolvableType resolvableType = ResolvableType.forClass(AbstractApplicationContextRunner.class, getClass());
 		Class<A> assertType = (Class<A>) resolvableType.resolveGeneric(1);
 		Class<C> contextType = (Class<C>) resolvableType.resolveGeneric(2);
-		return ApplicationContextAssertProvider.get(assertType, contextType, this::createAndLoadContext);
+		return ApplicationContextAssertProvider.get(assertType, contextType, () -> createAndLoadContext(refresh));
 	}
 
-	private C createAndLoadContext() {
+	private C createAndLoadContext(boolean refresh) {
 		C context = this.runnerConfiguration.contextFactory.get();
 		ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
 		if (beanFactory instanceof AbstractAutowireCapableBeanFactory) {
@@ -384,7 +400,7 @@ public abstract class AbstractApplicationContextRunner<SELF extends AbstractAppl
 			}
 		}
 		try {
-			configureContext(context);
+			configureContext(context, refresh);
 			return context;
 		}
 		catch (RuntimeException ex) {
@@ -393,7 +409,7 @@ public abstract class AbstractApplicationContextRunner<SELF extends AbstractAppl
 		}
 	}
 
-	private void configureContext(C context) {
+	private void configureContext(C context, boolean refresh) {
 		if (this.runnerConfiguration.parent != null) {
 			context.setParent(this.runnerConfiguration.parent);
 		}
@@ -408,7 +424,9 @@ public abstract class AbstractApplicationContextRunner<SELF extends AbstractAppl
 		if (classes.length > 0) {
 			((AnnotationConfigRegistry) context).register(classes);
 		}
-		context.refresh();
+		if (refresh) {
+			context.refresh();
+		}
 	}
 
 	private void accept(ContextConsumer<? super A> consumer, A context) {

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/context/runner/AbstractApplicationContextRunnerTests.java

@@ -47,6 +47,7 @@ import org.springframework.util.ClassUtils;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIOException;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 /**
  * Abstract tests for {@link AbstractApplicationContextRunner} implementations.
@@ -238,6 +239,16 @@ abstract class AbstractApplicationContextRunnerTests<T extends AbstractApplicati
 				.run((context) -> assertThat(context).hasSingleBean(ProfileConfig.class));
 	}
 
+	@Test
+	void prepareDoesNotRefreshContext() {
+		get().withUserConfiguration(FooConfig.class).prepare((context) -> {
+			assertThatIllegalStateException().isThrownBy(() -> context.getBean(String.class))
+					.withMessageContaining("not been refreshed");
+			context.getSourceApplicationContext().refresh();
+			assertThat(context.getBean(String.class)).isEqualTo("foo");
+		});
+	}
+
 	protected abstract T get();
 
 	private static void throwCheckedException(String message) throws IOException {