diff --git a/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorAsyncTest.java b/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorAsyncTest.java
index ff66b99e5a6..f74b54296ff 100644
--- a/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorAsyncTest.java
+++ b/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorAsyncTest.java
@@ -17,10 +17,12 @@
 import org.junit.runner.RunWith;
 import org.junit.runners.Parameterized;
 import org.mockito.Mock;
+import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.dom.Element;
+import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.internal.Range;
 import com.vaadin.flow.server.VaadinRequest;
 import com.vaadin.flow.server.VaadinService;
@@ -253,8 +255,10 @@ protected void init(VaadinRequest request) {
         private static VaadinSession findOrcreateSession() {
             VaadinSession session = VaadinSession.getCurrent();
             if (session == null) {
+                DeploymentConfiguration config = Mockito
+                        .mock(DeploymentConfiguration.class);
                 session = new AlwaysLockedVaadinSession(
-                        new VaadinServletService(new VaadinServlet(), null));
+                        new VaadinServletService(new VaadinServlet(), config));
                 VaadinSession.setCurrent(session);
             }
             return session;
diff --git a/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorTest.java b/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorTest.java
index 9db8449c794..c439c375b79 100644
--- a/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorTest.java
+++ b/flow-data/src/test/java/com/vaadin/flow/data/provider/DataCommunicatorTest.java
@@ -47,10 +47,12 @@
 import com.vaadin.flow.component.Tag;
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.dom.Element;
+import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.function.SerializableConsumer;
 import com.vaadin.flow.function.SerializablePredicate;
 import com.vaadin.flow.internal.Range;
 import com.vaadin.flow.internal.StateNode;
+import com.vaadin.flow.server.SessionLockCheckStrategy;
 import com.vaadin.flow.server.VaadinRequest;
 import com.vaadin.flow.server.VaadinService;
 import com.vaadin.flow.server.VaadinSession;
@@ -1805,7 +1807,15 @@ protected void init(VaadinRequest request) {
         private static VaadinSession findOrcreateSession() {
             VaadinSession session = VaadinSession.getCurrent();
             if (session == null) {
-                session = new AlwaysLockedVaadinSession(null);
+                VaadinService service = Mockito.mock(VaadinService.class);
+                DeploymentConfiguration conf = Mockito
+                        .mock(DeploymentConfiguration.class);
+                Mockito.when(conf.isProductionMode()).thenReturn(true);
+                Mockito.when(conf.getSessionLockCheckStrategy())
+                        .thenReturn(SessionLockCheckStrategy.ASSERT);
+                Mockito.when(service.getDeploymentConfiguration())
+                        .thenReturn(conf);
+                session = new AlwaysLockedVaadinSession(service);
                 VaadinSession.setCurrent(session);
             }
             return session;
diff --git a/flow-data/src/test/java/com/vaadin/flow/data/provider/hierarchy/HierarchicalCommunicatorDataTest.java b/flow-data/src/test/java/com/vaadin/flow/data/provider/hierarchy/HierarchicalCommunicatorDataTest.java
index 85a1c4a738b..1033bde33d6 100644
--- a/flow-data/src/test/java/com/vaadin/flow/data/provider/hierarchy/HierarchicalCommunicatorDataTest.java
+++ b/flow-data/src/test/java/com/vaadin/flow/data/provider/hierarchy/HierarchicalCommunicatorDataTest.java
@@ -20,22 +20,18 @@
 import java.util.List;
 import java.util.stream.IntStream;
 
-import com.vaadin.flow.function.SerializablePredicate;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
-import com.vaadin.flow.component.UI;
 import com.vaadin.flow.data.provider.CompositeDataGenerator;
 import com.vaadin.flow.data.provider.DataCommunicatorTest;
 import com.vaadin.flow.data.provider.hierarchy.HierarchicalArrayUpdater.HierarchicalUpdate;
 import com.vaadin.flow.dom.Element;
+import com.vaadin.flow.function.SerializablePredicate;
 import com.vaadin.flow.function.ValueProvider;
-import com.vaadin.flow.server.VaadinRequest;
-import com.vaadin.flow.server.VaadinService;
-import com.vaadin.flow.server.VaadinSession;
 
 import elemental.json.JsonValue;
 
@@ -79,7 +75,7 @@ public int hashCode() {
     private TreeDataProvider<Item> dataProvider;
     private HierarchicalDataCommunicator<Item> communicator;
     private TreeData<Item> treeData;
-    private MockUI ui;
+    private DataCommunicatorTest.MockUI ui;
     private Element element;
 
     private boolean parentClearCalled = false;
@@ -137,7 +133,7 @@ public void initialize() {
     @Before
     public void setUp() {
         MockitoAnnotations.initMocks(this);
-        ui = new MockUI();
+        ui = new DataCommunicatorTest.MockUI();
         element = new Element("div");
         ui.getElement().appendChild(element);
 
@@ -289,41 +285,4 @@ private void fakeClientCommunication() {
         });
     }
 
-    public static class MockUI extends UI {
-
-        public MockUI() {
-            this(findOrCreateSession());
-        }
-
-        public MockUI(VaadinSession session) {
-            getInternals().setSession(session);
-            setCurrent(this);
-        }
-
-        @Override
-        protected void init(VaadinRequest request) {
-            // Do nothing
-        }
-
-        private static VaadinSession findOrCreateSession() {
-            VaadinSession session = VaadinSession.getCurrent();
-            if (session == null) {
-                session = new DataCommunicatorTest.AlwaysLockedVaadinSession(
-                        null);
-                VaadinSession.setCurrent(session);
-            }
-            return session;
-        }
-    }
-
-    public static class AlwaysLockedVaadinSession
-            extends DataCommunicatorTest.MockVaadinSession {
-
-        public AlwaysLockedVaadinSession(VaadinService service) {
-            super(service);
-            lock();
-        }
-
-    }
-
 }
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java
index 53a93669623..8339de02282 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinService.java
@@ -936,8 +936,6 @@ private VaadinSession createAndRegisterSession(VaadinRequest request) {
         // Initial WebBrowser data comes from the request
         session.setBrowser(new WebBrowser(request));
 
-        session.setConfiguration(getDeploymentConfiguration());
-
         // Initial locale comes from the request
         if (getInstantiator().getI18NProvider() != null) {
             setLocale(request, session);
diff --git a/flow-server/src/main/java/com/vaadin/flow/server/VaadinSession.java b/flow-server/src/main/java/com/vaadin/flow/server/VaadinSession.java
index 3c8d940fef9..f80070d34a3 100644
--- a/flow-server/src/main/java/com/vaadin/flow/server/VaadinSession.java
+++ b/flow-server/src/main/java/com/vaadin/flow/server/VaadinSession.java
@@ -78,11 +78,6 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
 
     volatile boolean sessionClosedExplicitly = false;
 
-    /**
-     * Configuration for the session.
-     */
-    private DeploymentConfiguration configuration;
-
     /**
      * Default locale of the session.
      */
@@ -144,7 +139,11 @@ public class VaadinSession implements HttpSessionBindingListener, Serializable {
      *            the Vaadin service for the new session
      */
     public VaadinSession(VaadinService service) {
+        Objects.requireNonNull(service, "VaadinService can not be null.");
         this.service = service;
+
+        refreshSessionLockCheckStrategy();
+
         resourceRegistry = createStreamResourceRegistry();
     }
 
@@ -344,33 +343,24 @@ private void refreshLock() {
         lock = service.getSessionLock(session);
     }
 
-    public void setConfiguration(DeploymentConfiguration configuration) {
-        checkHasLock();
-        if (configuration == null) {
-            throw new IllegalArgumentException("Can not set to null");
-        }
-        checkSetConfiguration();
-        this.configuration = configuration;
-
-        sessionLockCheckStrategy = configuration.isProductionMode()
-                ? configuration.getSessionLockCheckStrategy()
+    /**
+     * Updates the session lock check strategy.
+     */
+    private void refreshSessionLockCheckStrategy() {
+        sessionLockCheckStrategy = getConfiguration().isProductionMode()
+                ? getConfiguration().getSessionLockCheckStrategy()
                 : SessionLockCheckStrategy.THROW;
         assert sessionLockCheckStrategy != null;
     }
 
-    protected void checkSetConfiguration() {
-        assert this.configuration == null
-                : "Configuration can only be set once";
-    }
-
     /**
-     * Gets the configuration for this session.
+     * Gets the deployment configuration. Delegates the call to
+     * {@link VaadinService#getDeploymentConfiguration()}
      *
      * @return the deployment configuration
      */
     public DeploymentConfiguration getConfiguration() {
-        checkHasLock();
-        return configuration;
+        return service.getDeploymentConfiguration();
     }
 
     /**
@@ -1117,6 +1107,8 @@ public void refreshTransients(WrappedSession wrappedSession,
             VaadinService vaadinService) {
         session = wrappedSession;
         service = vaadinService;
+
+        refreshSessionLockCheckStrategy();
         refreshLock();
     }
 
diff --git a/flow-server/src/test/java/com/vaadin/flow/component/InvalidUrlTest.java b/flow-server/src/test/java/com/vaadin/flow/component/InvalidUrlTest.java
index b1fc3a341b8..23473ffa8bd 100644
--- a/flow-server/src/test/java/com/vaadin/flow/component/InvalidUrlTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/component/InvalidUrlTest.java
@@ -80,18 +80,19 @@ private static void initUI(UI ui, String initialLocation,
             public VaadinContext getContext() {
                 return new MockVaadinContext();
             }
+
+            @Override
+            public DeploymentConfiguration getDeploymentConfiguration() {
+                DeploymentConfiguration config = Mockito
+                        .mock(DeploymentConfiguration.class);
+                Mockito.when(config.isProductionMode()).thenReturn(false);
+                return config;
+            }
         };
         service.setCurrentInstances(request, response);
 
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
 
-        DeploymentConfiguration config = Mockito
-                .mock(DeploymentConfiguration.class);
-        Mockito.when(config.isProductionMode()).thenReturn(false);
-
-        session.lock();
-        session.setConfiguration(config);
-
         ui.getInternals().setSession(session);
 
         RouteConfiguration routeConfiguration = RouteConfiguration
@@ -106,8 +107,6 @@ public VaadinContext getContext() {
         ui.doInit(request, 0);
         ui.getRouter().initializeUI(ui, UITest.requestToLocation(request));
 
-        session.unlock();
-
         if (statusCodeCaptor != null) {
             Mockito.verify(response).setStatus(statusCodeCaptor.capture());
         }
diff --git a/flow-server/src/test/java/com/vaadin/flow/component/LocationObserverTest.java b/flow-server/src/test/java/com/vaadin/flow/component/LocationObserverTest.java
index 1ae7145ff94..0c9bde1dc6a 100644
--- a/flow-server/src/test/java/com/vaadin/flow/component/LocationObserverTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/component/LocationObserverTest.java
@@ -71,9 +71,7 @@ private static VaadinSession createMockSession(Router router) {
             MockVaadinServletService service = new MockVaadinServletService();
             service.setRouter(router);
 
-            VaadinSession session = new AlwaysLockedVaadinSession(service);
-            session.setConfiguration(service.getDeploymentConfiguration());
-            return session;
+            return new AlwaysLockedVaadinSession(service);
         }
 
         @Override
diff --git a/flow-server/src/test/java/com/vaadin/flow/component/UITest.java b/flow-server/src/test/java/com/vaadin/flow/component/UITest.java
index 8215436088b..0ae67679bf4 100644
--- a/flow-server/src/test/java/com/vaadin/flow/component/UITest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/component/UITest.java
@@ -230,18 +230,19 @@ private static void initUI(UI ui, String initialLocation,
             public VaadinContext getContext() {
                 return new MockVaadinContext();
             }
+
+            @Override
+            public DeploymentConfiguration getDeploymentConfiguration() {
+                DeploymentConfiguration config = Mockito
+                        .mock(DeploymentConfiguration.class);
+                Mockito.when(config.isProductionMode()).thenReturn(false);
+                return config;
+            }
         };
         service.setCurrentInstances(request, response);
 
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-
-        DeploymentConfiguration config = Mockito
-                .mock(DeploymentConfiguration.class);
-        Mockito.when(config.isProductionMode()).thenReturn(false);
-
         session.lock();
-        session.setConfiguration(config);
-
         ui.getInternals().setSession(session);
 
         RouteConfiguration routeConfiguration = RouteConfiguration
diff --git a/flow-server/src/test/java/com/vaadin/flow/component/internal/UIInternalsTest.java b/flow-server/src/test/java/com/vaadin/flow/component/internal/UIInternalsTest.java
index 15d49b51253..4080f628215 100644
--- a/flow-server/src/test/java/com/vaadin/flow/component/internal/UIInternalsTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/component/internal/UIInternalsTest.java
@@ -39,6 +39,7 @@
 import com.vaadin.flow.shared.Registration;
 import com.vaadin.flow.shared.communication.PushMode;
 import com.vaadin.tests.util.AlwaysLockedVaadinSession;
+import com.vaadin.tests.util.MockDeploymentConfiguration;
 
 public class UIInternalsTest {
 
@@ -118,6 +119,10 @@ public void init() {
         Element body = new Element("body");
         Mockito.when(ui.getElement()).thenReturn(body);
 
+        MockDeploymentConfiguration config = new MockDeploymentConfiguration();
+        Mockito.when(vaadinService.getDeploymentConfiguration())
+                .thenReturn(config);
+
         internals = new UIInternals(ui);
         AlwaysLockedVaadinSession session = new AlwaysLockedVaadinSession(
                 vaadinService);
diff --git a/flow-server/src/test/java/com/vaadin/flow/component/webcomponent/WebComponentWrapperTest.java b/flow-server/src/test/java/com/vaadin/flow/component/webcomponent/WebComponentWrapperTest.java
index 5d43203e231..096df558355 100644
--- a/flow-server/src/test/java/com/vaadin/flow/component/webcomponent/WebComponentWrapperTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/component/webcomponent/WebComponentWrapperTest.java
@@ -23,6 +23,7 @@
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Test;
+import org.mockito.Mockito;
 
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.Tag;
@@ -36,6 +37,7 @@
 import com.vaadin.flow.server.VaadinSession;
 import com.vaadin.flow.server.webcomponent.WebComponentBinding;
 import com.vaadin.tests.util.AlwaysLockedVaadinSession;
+import com.vaadin.tests.util.MockDeploymentConfiguration;
 
 import elemental.json.Json;
 import static org.mockito.Mockito.mock;
@@ -242,9 +244,13 @@ private static WebComponentUI constructWebComponentUI(
         Element body = new Element("body");
         when(ui.getElement()).thenReturn(body);
 
+        VaadinService vaadinService = Mockito.mock(VaadinService.class);
+        MockDeploymentConfiguration config = new MockDeploymentConfiguration();
+        Mockito.when(vaadinService.getDeploymentConfiguration())
+                .thenReturn(config);
+
         UIInternals internals = new UIInternals(ui);
-        internals.setSession(
-                new AlwaysLockedVaadinSession(mock(VaadinService.class)));
+        internals.setSession(new AlwaysLockedVaadinSession(vaadinService));
         when(ui.getInternals()).thenReturn(internals);
 
         Component parent = new Parent();
diff --git a/flow-server/src/test/java/com/vaadin/flow/router/RouteConfigurationTest.java b/flow-server/src/test/java/com/vaadin/flow/router/RouteConfigurationTest.java
index f14a490c6fd..7854d26498d 100644
--- a/flow-server/src/test/java/com/vaadin/flow/router/RouteConfigurationTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/router/RouteConfigurationTest.java
@@ -31,6 +31,7 @@
 import com.vaadin.flow.server.VaadinServletService;
 import com.vaadin.flow.server.VaadinSession;
 import com.vaadin.flow.server.startup.ApplicationRouteRegistry;
+import com.vaadin.tests.util.MockDeploymentConfiguration;
 
 @NotThreadSafe
 public class RouteConfigurationTest {
@@ -50,6 +51,9 @@ public void init() {
         vaadinService = Mockito.mock(MockService.class);
         Mockito.when(vaadinService.getRouteRegistry()).thenReturn(registry);
         Mockito.when(vaadinService.getContext()).thenReturn(vaadinContext);
+        MockDeploymentConfiguration config = new MockDeploymentConfiguration();
+        Mockito.when(vaadinService.getDeploymentConfiguration())
+                .thenReturn(config);
 
         VaadinService.setCurrent(vaadinService);
 
diff --git a/flow-server/src/test/java/com/vaadin/flow/router/RouterConfigurationUrlResolvingTest.java b/flow-server/src/test/java/com/vaadin/flow/router/RouterConfigurationUrlResolvingTest.java
index 24ac6120d7a..fda7231193d 100644
--- a/flow-server/src/test/java/com/vaadin/flow/router/RouterConfigurationUrlResolvingTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/router/RouterConfigurationUrlResolvingTest.java
@@ -52,7 +52,6 @@ public void init() throws NoSuchFieldException, IllegalAccessException {
         super.init();
         ui = new RouterTestMockUI(router);
         ui.getSession().lock();
-        ui.getSession().setConfiguration(configuration);
 
         VaadinService.setCurrent(service);
 
diff --git a/flow-server/src/test/java/com/vaadin/flow/router/RouterTest.java b/flow-server/src/test/java/com/vaadin/flow/router/RouterTest.java
index 36030de0ff1..60c6cd7e944 100644
--- a/flow-server/src/test/java/com/vaadin/flow/router/RouterTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/router/RouterTest.java
@@ -1825,7 +1825,6 @@ public void init() throws NoSuchFieldException, SecurityException,
         super.init();
         ui = new RouterTestMockUI(router);
         ui.getSession().lock();
-        ui.getSession().setConfiguration(configuration);
 
         VaadinService.setCurrent(service);
 
diff --git a/flow-server/src/test/java/com/vaadin/flow/router/internal/ErrorStateRendererTest.java b/flow-server/src/test/java/com/vaadin/flow/router/internal/ErrorStateRendererTest.java
index 705fc13103b..93477472281 100644
--- a/flow-server/src/test/java/com/vaadin/flow/router/internal/ErrorStateRendererTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/router/internal/ErrorStateRendererTest.java
@@ -46,7 +46,6 @@
 import com.vaadin.flow.server.VaadinContext;
 import com.vaadin.flow.server.startup.ApplicationRouteRegistry;
 import com.vaadin.tests.util.AlwaysLockedVaadinSession;
-import com.vaadin.tests.util.MockDeploymentConfiguration;
 import com.vaadin.tests.util.MockUI;
 
 import elemental.json.Json;
@@ -221,7 +220,6 @@ public VaadinContext getContext() {
         };
 
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         MockUI ui = new MockUI(session);
         return ui;
diff --git a/flow-server/src/test/java/com/vaadin/flow/router/internal/NavigationStateRendererTest.java b/flow-server/src/test/java/com/vaadin/flow/router/internal/NavigationStateRendererTest.java
index 241c1415e7a..552aff33f27 100644
--- a/flow-server/src/test/java/com/vaadin/flow/router/internal/NavigationStateRendererTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/router/internal/NavigationStateRendererTest.java
@@ -68,7 +68,6 @@
 import com.vaadin.flow.server.ServiceException;
 import com.vaadin.flow.server.startup.ApplicationRouteRegistry;
 import com.vaadin.tests.util.AlwaysLockedVaadinSession;
-import com.vaadin.tests.util.MockDeploymentConfiguration;
 import com.vaadin.tests.util.MockUI;
 
 import elemental.json.Json;
@@ -287,7 +286,6 @@ public void handle_preserveOnRefreshAndWindowNameKnown_componentIsCachedRetrieve
 
         // given a locked session
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         // given a UI that contain a window name ROOT.123
         MockUI ui1 = new MockUI(session);
@@ -356,7 +354,6 @@ public void handle_preserveOnRefresh_refreshIsFlaggedInEvent() {
 
         // given a locked session
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         // given a UI that contain a window name ROOT.123
         MockUI ui = new MockUI(session);
@@ -409,7 +406,6 @@ public void handle_preserveOnRefresh_otherUIChildrenAreMoved() {
 
         // given a locked session
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         // given a NavigationStateRenderer mapping to PreservedView
         NavigationStateRenderer renderer = new NavigationStateRenderer(
@@ -456,7 +452,6 @@ public void handle_preserveOnRefreshView_routerLayoutIsPreserved_oldUiIsClosed()
 
         // given a locked session
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         // given a NavigationStateRenderer mapping to PreservedNestedView
         Router router = session.getService().getRouter();
@@ -510,7 +505,6 @@ public void handle_preserveOnRefresh_sameUI_uiIsNotClosed_childrenAreNotRemoved(
 
         // given a locked session
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         // given a NavigationStateRenderer mapping to PreservedView
         NavigationStateRenderer renderer = new NavigationStateRenderer(
@@ -582,7 +576,6 @@ public void handle_variousInputs_checkPushStateShouldBeCalledOrNot() {
 
         // given a locked session
         MockVaadinSession session = new AlwaysLockedVaadinSession(service);
-        session.setConfiguration(new MockDeploymentConfiguration());
 
         // given a NavigationStateRenderer mapping to RegularView
         new NavigationStateBuilder(router).withTarget(RegularView.class)
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/CustomUIClassLoaderTest.java b/flow-server/src/test/java/com/vaadin/flow/server/CustomUIClassLoaderTest.java
index 5cc5cbb60c3..c639cc8df63 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/CustomUIClassLoaderTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/CustomUIClassLoaderTest.java
@@ -10,7 +10,6 @@
 import com.vaadin.flow.component.UI;
 import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.server.startup.ApplicationConfiguration;
-import com.vaadin.tests.util.AlwaysLockedVaadinSession;
 
 import org.junit.Test;
 import org.mockito.Mockito;
@@ -52,9 +51,6 @@ protected synchronized Class<?> loadClass(String name, boolean resolve)
      */
     @Test
     public void testWithDefaultClassLoader() throws Exception {
-        VaadinSession application = createStubApplication();
-        application.setConfiguration(createConfigurationMock());
-
         Class<? extends UI> uiClass = BootstrapHandler
                 .getUIClass(createRequestMock(getClass().getClassLoader()));
 
@@ -113,13 +109,4 @@ public void testWithClassLoader() throws Exception {
                 loggingClassLoader.requestedClasses.get(0));
 
     }
-
-    private VaadinSession createStubApplication() {
-        return new AlwaysLockedVaadinSession(new MockVaadinServletService()) {
-            @Override
-            public DeploymentConfiguration getConfiguration() {
-                return createConfigurationMock();
-            }
-        };
-    }
 }
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/ErrorHandlerUtilTest.java b/flow-server/src/test/java/com/vaadin/flow/server/ErrorHandlerUtilTest.java
index a2c7b89d199..94efdfb4868 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/ErrorHandlerUtilTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/ErrorHandlerUtilTest.java
@@ -44,6 +44,7 @@
 import com.vaadin.flow.router.RouterLayout;
 import com.vaadin.flow.server.startup.ApplicationRouteRegistry;
 import com.vaadin.tests.util.AlwaysLockedVaadinSession;
+import com.vaadin.tests.util.MockDeploymentConfiguration;
 
 @NotThreadSafe
 public class ErrorHandlerUtilTest {
@@ -129,6 +130,10 @@ public void init() {
         Mockito.when(ui.getUI()).thenReturn(Optional.of(ui));
         Mockito.when(ui.getInternals()).thenReturn(internals);
 
+        MockDeploymentConfiguration config = new MockDeploymentConfiguration();
+        Mockito.when(vaadinService.getDeploymentConfiguration())
+                .thenReturn(config);
+
         session = new AlwaysLockedVaadinSession(vaadinService);
         VaadinContext context = new MockVaadinContext();
         Mockito.when(vaadinService.getContext()).thenReturn(context);
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/SessionRouteRegistryTest.java b/flow-server/src/test/java/com/vaadin/flow/server/SessionRouteRegistryTest.java
index 79eb5e4108b..fdc950571a2 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/SessionRouteRegistryTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/SessionRouteRegistryTest.java
@@ -31,6 +31,7 @@
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.HtmlContainer;
 import com.vaadin.flow.component.Tag;
+import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.internal.CurrentInstance;
 import com.vaadin.flow.router.BeforeEnterEvent;
 import com.vaadin.flow.router.BeforeEvent;
@@ -50,6 +51,7 @@
 import com.vaadin.flow.server.startup.ApplicationConfiguration;
 import com.vaadin.flow.server.startup.ApplicationRouteRegistry;
 import com.vaadin.flow.shared.Registration;
+import com.vaadin.tests.util.MockDeploymentConfiguration;
 
 public class SessionRouteRegistryTest {
 
@@ -76,6 +78,11 @@ public void init() {
         Mockito.when(applicationConfiguration.isProductionMode())
                 .thenReturn(true);
 
+        MockDeploymentConfiguration config = new MockDeploymentConfiguration();
+        config.setProductionMode(true);
+        Mockito.when(vaadinService.getDeploymentConfiguration())
+                .thenReturn(config);
+
         VaadinService.setCurrent(vaadinService);
 
         session = new MockVaadinSession(vaadinService) {
@@ -1239,5 +1246,10 @@ protected Lock getSessionLock(WrappedSession wrappedSession) {
         protected RouteRegistry getRouteRegistry() {
             return appRegistry;
         }
+
+        @Override
+        public DeploymentConfiguration getDeploymentConfiguration() {
+            return new MockDeploymentConfiguration();
+        }
     }
 }
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/VaadinSessionTest.java b/flow-server/src/test/java/com/vaadin/flow/server/VaadinSessionTest.java
index 1e7045f46ea..1c0903a75a3 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/VaadinSessionTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/VaadinSessionTest.java
@@ -20,6 +20,7 @@
 import java.io.IOException;
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
+import java.lang.reflect.Field;
 import java.util.EventObject;
 import java.util.HashMap;
 import java.util.Iterator;
@@ -34,6 +35,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.server.frontend.MockLogger;
 import jakarta.servlet.http.HttpServletRequest;
 import jakarta.servlet.http.HttpSession;
@@ -70,6 +72,8 @@ public UIDetachEvent(UI source) {
     public static class VaadinSessionWithMockLogger extends VaadinSession {
         public final MockLogger mockLogger = new MockLogger();
 
+        private DeploymentConfiguration config;
+
         public VaadinSessionWithMockLogger(VaadinService service) {
             super(service);
             mockLogger.includeStackTrace = true;
@@ -81,7 +85,11 @@ Logger getLogger() {
         }
 
         @Override
-        protected void checkSetConfiguration() {
+        public DeploymentConfiguration getConfiguration() {
+            if (config == null) {
+                config = new MockDeploymentConfiguration();
+            }
+            return config;
         }
     }
 
@@ -140,11 +148,6 @@ public Object getAttribute(String name) {
         session = new VaadinSessionWithMockLogger(mockService);
         mockService.storeSession(session, mockWrappedSession);
 
-        MockDeploymentConfiguration configuration = new MockDeploymentConfiguration();
-        session.lock();
-        session.setConfiguration(configuration);
-        session.unlock();
-
         ui = new UI();
         vaadinRequest = new VaadinServletRequest(
                 Mockito.mock(HttpServletRequest.class), mockService) {
@@ -496,7 +499,15 @@ public void valueUnbound_sessionIsNotInitialized_noAnyInteractions() {
     public static class TestVaadinSession extends VaadinSession {
 
         public TestVaadinSession() {
-            super(null);
+            super(new MockVaadinServletService());
+            try {
+                Field serviceField = getClass().getSuperclass()
+                        .getDeclaredField("service");
+                serviceField.setAccessible(true);
+                serviceField.set(this, null);
+            } catch (NoSuchFieldException | IllegalAccessException e) {
+                throw new RuntimeException(e);
+            }
         }
     }
 
@@ -545,13 +556,11 @@ public void checkHasLock_noCheckInDevMode() {
         session.checkHasLock();
 
         configuration.setLockCheckStrategy(SessionLockCheckStrategy.LOG);
-        session.setConfiguration(configuration);
         session.mockLogger.clearLogs();
         session.checkHasLock();
         Assert.assertEquals("", session.mockLogger.getLogs());
 
         configuration.setLockCheckStrategy(SessionLockCheckStrategy.ASSERT);
-        session.setConfiguration(configuration);
         session.checkHasLock();
     }
 
@@ -560,7 +569,7 @@ public void checkHasLock_assert() {
         final MockDeploymentConfiguration configuration = (MockDeploymentConfiguration) session
                 .getConfiguration();
         configuration.setProductionMode(true);
-        session.setConfiguration(configuration);
+        session.refreshTransients(mockWrappedSession, mockService);
         session.unlock();
         Assume.assumeFalse(session.hasLock());
 
@@ -581,7 +590,6 @@ public void checkHasLock_throw() {
                 .getConfiguration();
         configuration.setProductionMode(true);
         configuration.setLockCheckStrategy(SessionLockCheckStrategy.THROW);
-        session.setConfiguration(configuration);
         session.unlock();
         Assume.assumeFalse(session.hasLock());
 
@@ -600,7 +608,7 @@ public void checkHasLock_log() {
                 .getConfiguration();
         configuration.setProductionMode(true);
         configuration.setLockCheckStrategy(SessionLockCheckStrategy.LOG);
-        session.setConfiguration(configuration);
+        session.refreshTransients(mockWrappedSession, mockService);
         session.unlock();
         Assume.assumeFalse(session.hasLock());
 
diff --git a/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerViteTest.java b/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerViteTest.java
index c07d55a4e5f..e367e75c36e 100644
--- a/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerViteTest.java
+++ b/flow-server/src/test/java/com/vaadin/flow/server/communication/WebComponentBootstrapHandlerViteTest.java
@@ -199,7 +199,6 @@ protected PwaRegistry getPwaRegistry() {
 
         VaadinSession session = new MockVaadinSession(service);
         session.lock();
-        session.setConfiguration(service.getDeploymentConfiguration());
         MockDeploymentConfiguration config = (MockDeploymentConfiguration) service
                 .getDeploymentConfiguration();
         config.setFrontendHotdeploy(false);
@@ -234,7 +233,6 @@ public void writeBootstrapPage_devToolsDisabled()
 
         VaadinSession session = new MockVaadinSession(service);
         session.lock();
-        session.setConfiguration(service.getDeploymentConfiguration());
         MockDeploymentConfiguration config = (MockDeploymentConfiguration) service
                 .getDeploymentConfiguration();
         config.setFrontendHotdeploy(false);
@@ -300,7 +298,6 @@ public void writeBootstrapPage_withExportChunk()
 
         VaadinSession session = new MockVaadinSession(service);
         session.lock();
-        session.setConfiguration(service.getDeploymentConfiguration());
         MockDeploymentConfiguration config = (MockDeploymentConfiguration) service
                 .getDeploymentConfiguration();
         config.setFrontendHotdeploy(false);
@@ -334,7 +331,6 @@ public void writeBootstrapPage_noExportChunk()
 
         VaadinSession session = new MockVaadinSession(service);
         session.lock();
-        session.setConfiguration(service.getDeploymentConfiguration());
         MockDeploymentConfiguration config = (MockDeploymentConfiguration) service
                 .getDeploymentConfiguration();
         config.setApplicationOrSystemProperty(SERVLET_PARAMETER_STATISTICS_JSON,
diff --git a/flow-server/src/test/java/com/vaadin/tests/server/SerializationTest.java b/flow-server/src/test/java/com/vaadin/tests/server/SerializationTest.java
index 57be740c9e1..d7b38ea2b11 100644
--- a/flow-server/src/test/java/com/vaadin/tests/server/SerializationTest.java
+++ b/flow-server/src/test/java/com/vaadin/tests/server/SerializationTest.java
@@ -23,10 +23,9 @@
 import com.vaadin.flow.server.VaadinSession;
 import com.vaadin.flow.server.WrappedSession;
 import com.vaadin.flow.server.startup.ApplicationConfiguration;
+import com.vaadin.tests.util.MockDeploymentConfiguration;
 import com.vaadin.tests.util.MockUI;
 
-import static org.mockito.Mockito.withSettings;
-
 public class SerializationTest {
 
     @Test
@@ -64,8 +63,6 @@ public void testSerializeVaadinSession_notProductionMode_disableDevModeSerializa
         // should be called by Flow internally as soon as the session has
         // been created.
         session.refreshTransients(null, vaadinService);
-        session.setConfiguration(Mockito.mock(DeploymentConfiguration.class,
-                Mockito.withSettings().serializable()));
         MockUI ui = new MockUI(session);
         ui.doInit(null, 42);
         session.addUI(ui);
@@ -131,8 +128,6 @@ private static VaadinSession serializeAndDeserializeWithUI(
         // should be called by Flow internally as soon as the session has
         // been created.
         session.refreshTransients(null, vaadinService);
-        session.setConfiguration(Mockito.mock(DeploymentConfiguration.class,
-                withSettings().serializable()));
         MockUI ui = new MockUI(session);
         ui.doInit(null, 42);
         session.addUI(ui);
@@ -225,6 +220,13 @@ public MockVaadinService(boolean productionMode, boolean serialize) {
             this.serialize = serialize;
         }
 
+        @Override
+        public DeploymentConfiguration getDeploymentConfiguration() {
+            MockDeploymentConfiguration config = new MockDeploymentConfiguration();
+            config.setProductionMode(productionMode);
+            return config;
+        }
+
         @Override
         public VaadinContext getContext() {
             ApplicationConfiguration applicationConfiguration = Mockito
diff --git a/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java b/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java
index 2cb30d0f000..c592bf9a85d 100644
--- a/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java
+++ b/flow-server/src/test/java/com/vaadin/tests/util/MockUI.java
@@ -68,7 +68,8 @@ private static VaadinSession createSession() {
 
     private static VaadinSession createSession(Router router) {
         VaadinService service = Mockito.mock(VaadinService.class);
-
+        Mockito.when(service.getDeploymentConfiguration())
+                .thenReturn(createConfiguration());
         if (router != null) {
             Mockito.when(service.getRouter()).thenReturn(router);
         }
@@ -85,9 +86,6 @@ private static DeploymentConfiguration createConfiguration() {
     }
 
     public static MockUI createUI() {
-        DeploymentConfiguration configuration = createConfiguration();
-        VaadinSession session = createSession();
-        session.setConfiguration(configuration);
-        return new MockUI(session);
+        return new MockUI(createSession());
     }
 }
diff --git a/vaadin-dev-server/src/test/java/com/vaadin/base/devserver/themeeditor/AbstractThemeEditorTest.java b/vaadin-dev-server/src/test/java/com/vaadin/base/devserver/themeeditor/AbstractThemeEditorTest.java
index c53bbdf48d3..1a447b97fa4 100644
--- a/vaadin-dev-server/src/test/java/com/vaadin/base/devserver/themeeditor/AbstractThemeEditorTest.java
+++ b/vaadin-dev-server/src/test/java/com/vaadin/base/devserver/themeeditor/AbstractThemeEditorTest.java
@@ -1,12 +1,12 @@
 package com.vaadin.base.devserver.themeeditor;
 
 import com.vaadin.base.devserver.MockVaadinContext;
-import com.vaadin.experimental.FeatureFlags;
 import com.vaadin.flow.component.Component;
 import com.vaadin.flow.component.html.Span;
 import com.vaadin.flow.component.internal.ComponentTracker;
 import com.vaadin.flow.di.Lookup;
 import com.vaadin.flow.dom.Element;
+import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.server.Command;
 import com.vaadin.flow.server.VaadinContext;
 import com.vaadin.flow.server.VaadinService;
@@ -44,6 +44,8 @@ public abstract class AbstractThemeEditorTest {
     protected final int INLINEADD_CREATE = 48;
     protected final int INLINEADD_ATTACH = 48;
 
+    private VaadinSession session;
+
     protected class TestThemeModifier extends ThemeModifier {
 
         public TestThemeModifier() {
@@ -58,8 +60,6 @@ protected File getFrontendFolder() {
 
     protected class TestJavaSourceModifier extends JavaSourceModifier {
 
-        private VaadinSession session = new MockVaadinSession(null);
-
         public TestJavaSourceModifier() {
             super(mockContext);
         }
@@ -145,6 +145,13 @@ public void prepare() {
         VaadinService.setCurrent(service);
         Mockito.when(service.getContext()).thenReturn(mockContext);
 
+        DeploymentConfiguration depConf = Mockito
+                .mock(DeploymentConfiguration.class);
+        Mockito.when(depConf.isProductionMode()).thenReturn(false);
+        Mockito.when(service.getDeploymentConfiguration()).thenReturn(depConf);
+
+        session = new MockVaadinSession(service);
+
         ApplicationConfiguration configuration = Mockito
                 .mock(ApplicationConfiguration.class);
         ApplicationConfigurationFactory factory = Mockito
diff --git a/vaadin-spring/src/test/java/com/vaadin/flow/spring/scopes/AbstractScopeTest.java b/vaadin-spring/src/test/java/com/vaadin/flow/spring/scopes/AbstractScopeTest.java
index 8ee248caa07..b88763bb736 100644
--- a/vaadin-spring/src/test/java/com/vaadin/flow/spring/scopes/AbstractScopeTest.java
+++ b/vaadin-spring/src/test/java/com/vaadin/flow/spring/scopes/AbstractScopeTest.java
@@ -29,6 +29,7 @@
 import org.springframework.beans.factory.config.Scope;
 
 import com.vaadin.flow.di.Lookup;
+import com.vaadin.flow.function.DeploymentConfiguration;
 import com.vaadin.flow.server.DefaultDeploymentConfiguration;
 import com.vaadin.flow.server.VaadinContext;
 import com.vaadin.flow.server.VaadinService;
@@ -48,10 +49,19 @@ public abstract class AbstractScopeTest {
 
     public static class TestSession extends SpringVaadinSession {
 
+        private DeploymentConfiguration configuration;
+
         public TestSession() {
             super(Mockito.mock(VaadinService.class));
         }
 
+        @Override
+        public DeploymentConfiguration getConfiguration() {
+            if (configuration == null) {
+                configuration = Mockito.mock(DeploymentConfiguration.class);
+            }
+            return configuration;
+        }
     }
 
     @After