diff --git a/spring-test/src/main/java/org/springframework/mock/web/server/MockServerWebExchange.java b/spring-test/src/main/java/org/springframework/mock/web/server/MockServerWebExchange.java
index 580ebe1780..0f51d50103 100644
--- a/spring-test/src/main/java/org/springframework/mock/web/server/MockServerWebExchange.java
+++ b/spring-test/src/main/java/org/springframework/mock/web/server/MockServerWebExchange.java
@@ -109,8 +109,10 @@ public final class MockServerWebExchange extends DefaultServerWebExchange {
 
 		/**
 		 * Set the session to use for the exchange.
-		 * <p>This is mutually exclusive with {@link #sessionManager(WebSessionManager)}.
+		 * <p>This method is mutually exclusive with
+		 * {@link #sessionManager(WebSessionManager)}.
 		 * @param session the session to use
+		 * @see MockWebSession
 		 */
 		public Builder session(WebSession session) {
 			this.sessionManager = exchange -> Mono.just(session);
diff --git a/spring-test/src/main/java/org/springframework/mock/web/server/MockWebSession.java b/spring-test/src/main/java/org/springframework/mock/web/server/MockWebSession.java
new file mode 100644
index 0000000000..5bf53efbda
--- /dev/null
+++ b/spring-test/src/main/java/org/springframework/mock/web/server/MockWebSession.java
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2002-2018 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
+ *
+ *      http://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.mock.web.server;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Map;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.web.server.WebSession;
+import org.springframework.web.server.session.InMemoryWebSessionStore;
+
+/**
+ * Implementation of {@code WebSession} that delegates to a session instance
+ * obtained via {@link InMemoryWebSessionStore}.
+ *
+ * <p>This is intended for use with the
+ * {@link MockServerWebExchange.Builder#session(WebSession) session(WebSession)}
+ * method of the {@code MockServerWebExchange} builder, eliminating the need
+ * to use {@code WebSessionManager} or {@code WebSessionStore} altogether.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.1
+ */
+public class MockWebSession implements WebSession {
+
+	private final WebSession delegate;
+
+
+	public MockWebSession() {
+		this(null);
+	}
+
+	@SuppressWarnings("ConstantConditions")
+	public MockWebSession(Clock clock) {
+		InMemoryWebSessionStore sessionStore = new InMemoryWebSessionStore();
+		if (clock != null) {
+			sessionStore.setClock(clock);
+		}
+		this.delegate = sessionStore.createWebSession().block();
+	}
+
+
+	@Override
+	public String getId() {
+		return this.delegate.getId();
+	}
+
+	@Override
+	public Map<String, Object> getAttributes() {
+		return this.delegate.getAttributes();
+	}
+
+	@Override
+	public void start() {
+		this.delegate.start();
+	}
+
+	@Override
+	public boolean isStarted() {
+		return this.delegate.isStarted();
+	}
+
+	@Override
+	public Mono<Void> changeSessionId() {
+		return this.delegate.changeSessionId();
+	}
+
+	@Override
+	public Mono<Void> invalidate() {
+		return this.delegate.invalidate();
+	}
+
+	@Override
+	public Mono<Void> save() {
+		return this.delegate.save();
+	}
+
+	@Override
+	public boolean isExpired() {
+		return this.delegate.isExpired();
+	}
+
+	@Override
+	public Instant getCreationTime() {
+		return this.delegate.getCreationTime();
+	}
+
+	@Override
+	public Instant getLastAccessTime() {
+		return this.delegate.getLastAccessTime();
+	}
+
+	@Override
+	public void setMaxIdleTime(Duration maxIdleTime) {
+		this.delegate.setMaxIdleTime(maxIdleTime);
+	}
+
+	@Override
+	public Duration getMaxIdleTime() {
+		return this.delegate.getMaxIdleTime();
+	}
+
+}
diff --git a/spring-web/src/test/java/org/springframework/mock/web/test/server/MockWebSession.java b/spring-web/src/test/java/org/springframework/mock/web/test/server/MockWebSession.java
new file mode 100644
index 0000000000..3ac6ba09fb
--- /dev/null
+++ b/spring-web/src/test/java/org/springframework/mock/web/test/server/MockWebSession.java
@@ -0,0 +1,119 @@
+/*
+ * Copyright 2002-2018 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
+ *
+ *      http://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.mock.web.test.server;
+
+import java.time.Clock;
+import java.time.Duration;
+import java.time.Instant;
+import java.util.Map;
+
+import reactor.core.publisher.Mono;
+
+import org.springframework.web.server.WebSession;
+import org.springframework.web.server.session.InMemoryWebSessionStore;
+
+/**
+ * Implementation of {@code WebSession} that delegates to a session instance
+ * obtained via {@link InMemoryWebSessionStore}.
+ *
+ * <p>This is intended for use with the
+ * {@link MockServerWebExchange.Builder#session(WebSession) session(WebSession)}
+ * method of the {@code MockServerWebExchange} builder, eliminating the need
+ * to use {@code WebSessionManager} or {@code WebSessionStore} altogether.
+ *
+ * @author Rossen Stoyanchev
+ * @since 5.1
+ */
+public class MockWebSession implements WebSession {
+
+	private final WebSession delegate;
+
+
+	public MockWebSession() {
+		this(null);
+	}
+
+	@SuppressWarnings("ConstantConditions")
+	public MockWebSession(Clock clock) {
+		InMemoryWebSessionStore sessionStore = new InMemoryWebSessionStore();
+		if (clock != null) {
+			sessionStore.setClock(clock);
+		}
+		this.delegate = sessionStore.createWebSession().block();
+	}
+
+
+	@Override
+	public String getId() {
+		return this.delegate.getId();
+	}
+
+	@Override
+	public Map<String, Object> getAttributes() {
+		return this.delegate.getAttributes();
+	}
+
+	@Override
+	public void start() {
+		this.delegate.start();
+	}
+
+	@Override
+	public boolean isStarted() {
+		return this.delegate.isStarted();
+	}
+
+	@Override
+	public Mono<Void> changeSessionId() {
+		return this.delegate.changeSessionId();
+	}
+
+	@Override
+	public Mono<Void> invalidate() {
+		return this.delegate.invalidate();
+	}
+
+	@Override
+	public Mono<Void> save() {
+		return this.delegate.save();
+	}
+
+	@Override
+	public boolean isExpired() {
+		return this.delegate.isExpired();
+	}
+
+	@Override
+	public Instant getCreationTime() {
+		return this.delegate.getCreationTime();
+	}
+
+	@Override
+	public Instant getLastAccessTime() {
+		return this.delegate.getLastAccessTime();
+	}
+
+	@Override
+	public void setMaxIdleTime(Duration maxIdleTime) {
+		this.delegate.setMaxIdleTime(maxIdleTime);
+	}
+
+	@Override
+	public Duration getMaxIdleTime() {
+		return this.delegate.getMaxIdleTime();
+	}
+
+}
diff --git a/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SessionAttributesHandlerTests.java b/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SessionAttributesHandlerTests.java
index 598b62c346..25c1808cf4 100644
--- a/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SessionAttributesHandlerTests.java
+++ b/spring-webflux/src/test/java/org/springframework/web/reactive/result/method/annotation/SessionAttributesHandlerTests.java
@@ -21,11 +21,11 @@ import java.util.HashSet;
 
 import org.junit.Test;
 
+import org.springframework.mock.web.test.server.MockWebSession;
 import org.springframework.tests.sample.beans.TestBean;
 import org.springframework.ui.ModelMap;
 import org.springframework.web.bind.annotation.SessionAttributes;
 import org.springframework.web.server.WebSession;
-import org.springframework.web.server.session.InMemoryWebSessionStore;
 
 import static java.util.Arrays.*;
 import static org.junit.Assert.*;
@@ -50,9 +50,7 @@ public class SessionAttributesHandlerTests {
 
 	@Test
 	public void retrieveAttributes() {
-		WebSession session = new InMemoryWebSessionStore().createWebSession().block();
-		assertNotNull(session);
-
+		WebSession session = new MockWebSession();
 		session.getAttributes().put("attr1", "value1");
 		session.getAttributes().put("attr2", "value2");
 		session.getAttributes().put("attr3", new TestBean());
@@ -72,9 +70,7 @@ public class SessionAttributesHandlerTests {
 
 	@Test
 	public void cleanupAttributes() {
-		WebSession session = new InMemoryWebSessionStore().createWebSession().block();
-		assertNotNull(session);
-
+		WebSession session = new MockWebSession();
 		session.getAttributes().put("attr1", "value1");
 		session.getAttributes().put("attr2", "value2");
 		session.getAttributes().put("attr3", new TestBean());
@@ -94,14 +90,13 @@ public class SessionAttributesHandlerTests {
 
 	@Test
 	public void storeAttributes() {
-		WebSession session = new InMemoryWebSessionStore().createWebSession().block();
-		assertNotNull(session);
 
 		ModelMap model = new ModelMap();
 		model.put("attr1", "value1");
 		model.put("attr2", "value2");
 		model.put("attr3", new TestBean());
 
+		WebSession session = new MockWebSession();
 		sessionAttributesHandler.storeAttributes(session, model);
 
 		assertEquals("value1", session.getAttributes().get("attr1"));