feat: enable SignalTest and add slf4j-simple for test logging

- Applied SignalsPlugin fix from bcb43396b (getIdentifier() ?? add() pattern)
- Converted SignalTest to use AbstractFullStackTest
- Created SignalEndpoint.ts snapshot with correct type imports
- Added slf4j-simple test dependency to eliminate SLF4J warnings
- Updated full-stack-test.md progress (5/47 tests converted)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: Artur-

packages/java/typescript-generator/full-stack-test.md

@@ -25,16 +25,16 @@ Transform the testing approach from separate Java→OpenAPI and OpenAPI→TypeSc
 - TypeScriptComparator.java ✅
 - **AbstractFullStackTest.java** ✅ (base class with all configuration)
 
-**Phase 2: Convert Tests** 🔄 IN PROGRESS (4/47 converted)
+**Phase 2: Convert Tests** 🔄 IN PROGRESS (5/47 converted)
 
-**Transfertypes Plugin (4/8):**
+**Transfertypes Plugin (5/8):**
 - ✅ UUIDTest (cleaned: removed connect-client.default.ts, endpoints.ts)
 - ✅ JsonNodeTest (cleaned: removed connect-client.default.ts, endpoints.ts)
 - ✅ MultipartFileTest (cleaned: removed connect-client.default.ts, endpoints.ts)
 - ✅ PushTypeTest (cleaned: removed connect-client.default.ts, endpoints.ts)
+- ✅ SignalTest (applied SignalsPlugin fix from bcb43396b)
 - ⏳ PageableTest
 - ⏳ BarePageableTest
-- ⏳ SignalTest (requires SignalsPlugin fix)
 - ⏳ MultipartFileMisuseTest
 
 **Other Plugins (~40 remaining):**

packages/java/typescript-generator/pom.xml

@@ -177,6 +177,11 @@
       <artifactId>spring-web</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-simple</artifactId>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <build>

packages/java/typescript-generator/src/test/java/com/vaadin/hilla/parser/plugins/transfertypes/signals/SignalTest.java

@@ -15,32 +15,19 @@
  */
 package com.vaadin.hilla.parser.plugins.transfertypes.signals;
 
-import java.io.IOException;
-import java.net.URISyntaxException;
-import java.util.List;
-import java.util.Set;
-
 import org.junit.jupiter.api.Test;
 
-import com.vaadin.hilla.parser.core.Parser;
-import com.vaadin.hilla.parser.plugins.backbone.BackbonePlugin;
-import com.vaadin.hilla.parser.plugins.transfertypes.TransferTypesPlugin;
-import com.vaadin.hilla.parser.plugins.transfertypes.test.helpers.TestHelper;
-import com.vaadin.hilla.parser.testutils.annotations.Endpoint;
+import com.vaadin.hilla.parser.testutils.AbstractFullStackTest;
 
-public class SignalTest {
-    private final TestHelper helper = new TestHelper(getClass());
+/**
+ * Full-stack test for Signal type handling - verifies complete Java →
+ * TypeScript generation pipeline.
+ */
+public class SignalTest extends AbstractFullStackTest {
 
     @Test
     public void should_ReplaceSignalClassesWithLocalSignalRecords()
-            throws IOException, URISyntaxException {
-        var openAPI = new Parser()
-                .classPath(Set.of(helper.getTargetDir().toString()))
-                .endpointAnnotations(List.of(Endpoint.class))
-                .addPlugin(new BackbonePlugin())
-                .addPlugin(new TransferTypesPlugin())
-                .execute(List.of(SignalEndpoint.class));
-
-        helper.executeParserWithConfig(openAPI);
+            throws Exception {
+        assertTypescriptMatchesSnapshot(SignalEndpoint.class);
     }
 }

packages/java/typescript-generator/src/test/java/com/vaadin/hilla/parser/testutils/AbstractFullStackTest.java

@@ -119,8 +119,7 @@ protected void assertTypescriptMatchesSnapshot(Class<?>... endpointClasses)
                 .endpointExposedAnnotations(List.of(EndpointExposed.class))
                 .addPlugin(new BackbonePlugin())
                 .addPlugin(new TransferTypesPlugin())
-                .addPlugin(new ModelPlugin())
-                .addPlugin(new NonnullPlugin())
+                .addPlugin(new ModelPlugin()).addPlugin(new NonnullPlugin())
                 .addPlugin(new SubTypesPlugin())
                 .addPlugin(new MultipartFileCheckerPlugin())
                 .execute(Arrays.asList(endpointClasses));
@@ -148,7 +147,8 @@ private GeneratedFiles executeFullStack(OpenAPI openAPI)
             // Find the run-generator.mjs script
             Path scriptPath = findGeneratorScript();
 
-            // Write OpenAPI JSON to temp file (FrontendUtils doesn't support stdin piping)
+            // Write OpenAPI JSON to temp file (FrontendUtils doesn't support
+            // stdin piping)
             Path tempFile = Files.createTempFile("openapi", ".json");
             String output;
             try {

packages/java/typescript-generator/src/test/resources/com/vaadin/hilla/parser/plugins/transfertypes/signals/snapshots/.gitkeep

@@ -0,0 +1,11 @@
+import { EndpointRequestInit as EndpointRequestInit_1 } from "@vaadin/hilla-frontend";
+import type ListSignal_1 from "./com/vaadin/hilla/runtime/transfertypes/ListSignal.js";
+import type NumberSignal_1 from "./com/vaadin/hilla/runtime/transfertypes/NumberSignal.js";
+import type Signal_1 from "./com/vaadin/hilla/runtime/transfertypes/Signal.js";
+import type ValueSignal_1 from "./com/vaadin/hilla/runtime/transfertypes/ValueSignal.js";
+import client_1 from "./connect-client.default.js";
+async function getNumberSignal_1(init?: EndpointRequestInit_1): Promise<NumberSignal_1 | undefined> { return client_1.call("SignalEndpoint", "getNumberSignal", {}, init); }
+async function getStringListSignal_1(init?: EndpointRequestInit_1): Promise<ListSignal_1<string | undefined> | undefined> { return client_1.call("SignalEndpoint", "getStringListSignal", {}, init); }
+async function getStringSignal_1(init?: EndpointRequestInit_1): Promise<Signal_1<string | undefined> | undefined> { return client_1.call("SignalEndpoint", "getStringSignal", {}, init); }
+async function getStringValueSignal_1(init?: EndpointRequestInit_1): Promise<ValueSignal_1<string | undefined> | undefined> { return client_1.call("SignalEndpoint", "getStringValueSignal", {}, init); }
+export { getNumberSignal_1 as getNumberSignal, getStringListSignal_1 as getStringListSignal, getStringSignal_1 as getStringSignal, getStringValueSignal_1 as getStringValueSignal };

packages/java/typescript-generator/src/test/resources/com/vaadin/hilla/parser/plugins/transfertypes/signals/snapshots/SignalEndpoint.ts

@@ -59,12 +59,11 @@ export default class SignalProcessor {
         if (isFunctionDeclaration(node)) {
           // Check if the function is a signal method.
           if (node.name && this.#methods.has(node.name.text)) {
-            // Get the signal class ID that was already imported in
-            // TransferTypes plugin.
-            const signalId = imports.named.getIdentifier(
-              HILLA_REACT_SIGNALS,
-              simplifyFullyQualifiedName(this.#methods.get(node.name.text)!),
-            )!;
+            // Get or add the signal class identifier for runtime use.
+            const signalClassName = simplifyFullyQualifiedName(this.#methods.get(node.name.text)!);
+            const signalId =
+              imports.named.getIdentifier(HILLA_REACT_SIGNALS, signalClassName) ??
+              imports.named.add(HILLA_REACT_SIGNALS, signalClassName);
 
             // Remove the `init` parameter.
             const params = node.parameters.filter(