Configure a RestClient.Builder with RestClientTest

This commit adds support for configuring a `RestClient.Builder` and
`MockRestServiceServer` support for the `RestClient` when using
`@RestClientTest` sliced tests.

Closes gh-37033

spring-boot-project/spring-boot-test/src/test/java/org/springframework/boot/test/web/client/MockServerRestClientCustomizerTests.java

@@ -0,0 +1,163 @@
+/*
+ * Copyright 2012-2023 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.test.web.client;
+
+import java.util.function.Supplier;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.test.web.client.RequestExpectationManager;
+import org.springframework.test.web.client.SimpleRequestExpectationManager;
+import org.springframework.test.web.client.UnorderedRequestExpectationManager;
+import org.springframework.web.client.RestClient;
+import org.springframework.web.client.RestClient.Builder;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
+import static org.springframework.test.web.client.match.MockRestRequestMatchers.requestTo;
+import static org.springframework.test.web.client.response.MockRestResponseCreators.withSuccess;
+
+/**
+ * Tests for {@link MockServerRestClientCustomizer}.
+ *
+ * @author Scott Frederick
+ */
+class MockServerRestClientCustomizerTests {
+
+	private MockServerRestClientCustomizer customizer;
+
+	@BeforeEach
+	void setup() {
+		this.customizer = new MockServerRestClientCustomizer();
+	}
+
+	@Test
+	void createShouldUseSimpleRequestExpectationManager() {
+		MockServerRestClientCustomizer customizer = new MockServerRestClientCustomizer();
+		customizer.customize(RestClient.builder());
+		assertThat(customizer.getServer()).extracting("expectationManager")
+			.isInstanceOf(SimpleRequestExpectationManager.class);
+	}
+
+	@Test
+	void createWhenExpectationManagerClassIsNullShouldThrowException() {
+		Class<? extends RequestExpectationManager> expectationManager = null;
+		assertThatIllegalArgumentException().isThrownBy(() -> new MockServerRestClientCustomizer(expectationManager))
+			.withMessageContaining("ExpectationManager must not be null");
+	}
+
+	@Test
+	void createWhenExpectationManagerSupplierIsNullShouldThrowException() {
+		Supplier<? extends RequestExpectationManager> expectationManagerSupplier = null;
+		assertThatIllegalArgumentException()
+			.isThrownBy(() -> new MockServerRestClientCustomizer(expectationManagerSupplier))
+			.withMessageContaining("ExpectationManagerSupplier must not be null");
+	}
+
+	@Test
+	void createShouldUseExpectationManagerClass() {
+		MockServerRestClientCustomizer customizer = new MockServerRestClientCustomizer(
+				UnorderedRequestExpectationManager.class);
+		customizer.customize(RestClient.builder());
+		assertThat(customizer.getServer()).extracting("expectationManager")
+			.isInstanceOf(UnorderedRequestExpectationManager.class);
+	}
+
+	@Test
+	void createShouldUseSupplier() {
+		MockServerRestClientCustomizer customizer = new MockServerRestClientCustomizer(
+				UnorderedRequestExpectationManager::new);
+		customizer.customize(RestClient.builder());
+		assertThat(customizer.getServer()).extracting("expectationManager")
+			.isInstanceOf(UnorderedRequestExpectationManager.class);
+	}
+
+	@Test
+	void customizeShouldBindServer() {
+		Builder builder = RestClient.builder();
+		this.customizer.customize(builder);
+		this.customizer.getServer().expect(requestTo("/test")).andRespond(withSuccess());
+		builder.build().get().uri("/test").retrieve().toEntity(String.class);
+		this.customizer.getServer().verify();
+	}
+
+	@Test
+	void getServerWhenNoServersAreBoundShouldThrowException() {
+		assertThatIllegalStateException().isThrownBy(this.customizer::getServer)
+			.withMessageContaining("Unable to return a single MockRestServiceServer since "
+					+ "MockServerRestClientCustomizer has not been bound to a RestClient");
+	}
+
+	@Test
+	void getServerWhenMultipleServersAreBoundShouldThrowException() {
+		this.customizer.customize(RestClient.builder());
+		this.customizer.customize(RestClient.builder());
+		assertThatIllegalStateException().isThrownBy(this.customizer::getServer)
+			.withMessageContaining("Unable to return a single MockRestServiceServer since "
+					+ "MockServerRestClientCustomizer has been bound to more than one RestClient");
+	}
+
+	@Test
+	void getServerWhenSingleServerIsBoundShouldReturnServer() {
+		Builder builder = RestClient.builder();
+		this.customizer.customize(builder);
+		assertThat(this.customizer.getServer()).isEqualTo(this.customizer.getServer(builder));
+	}
+
+	@Test
+	void getServerWhenRestClientBuilderIsFoundShouldReturnServer() {
+		Builder builder1 = RestClient.builder();
+		Builder builder2 = RestClient.builder();
+		this.customizer.customize(builder1);
+		this.customizer.customize(builder2);
+		assertThat(this.customizer.getServer(builder1)).isNotNull();
+		assertThat(this.customizer.getServer(builder2)).isNotNull().isNotSameAs(this.customizer.getServer(builder1));
+	}
+
+	@Test
+	void getServerWhenRestClientBuilderIsNotFoundShouldReturnNull() {
+		Builder builder1 = RestClient.builder();
+		Builder builder2 = RestClient.builder();
+		this.customizer.customize(builder1);
+		assertThat(this.customizer.getServer(builder1)).isNotNull();
+		assertThat(this.customizer.getServer(builder2)).isNull();
+	}
+
+	@Test
+	void getServersShouldReturnServers() {
+		Builder builder1 = RestClient.builder();
+		Builder builder2 = RestClient.builder();
+		this.customizer.customize(builder1);
+		this.customizer.customize(builder2);
+		assertThat(this.customizer.getServers()).containsOnlyKeys(builder1, builder2);
+	}
+
+	@Test
+	void getExpectationManagersShouldReturnExpectationManagers() {
+		Builder builder1 = RestClient.builder();
+		Builder builder2 = RestClient.builder();
+		this.customizer.customize(builder1);
+		this.customizer.customize(builder2);
+		RequestExpectationManager manager1 = this.customizer.getExpectationManagers().get(builder1);
+		RequestExpectationManager manager2 = this.customizer.getExpectationManagers().get(builder2);
+		assertThat(this.customizer.getServer(builder1)).extracting("expectationManager").isEqualTo(manager1);
+		assertThat(this.customizer.getServer(builder2)).extracting("expectationManager").isEqualTo(manager2);
+	}
+
+}