test: Introduce AdkWebServerUITest

This WORKS and will not yet actually reproduce the
#302 problem.

This because that is a packaging problem, which this
kind of test cannot detect. It still seems valuable to
have such a test here though anyway.

A future follow-up contribution on this might add the
missing test coverage for the actual packaging problem.

Author: vorburger

dev/src/test/java/com/google/adk/web/AdkWebServerUITest.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2025 Google LLC
+ *
+ * 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 com.google.adk.web;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.redirectedUrl;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+/**
+ * Integration tests for the {@link AdkWebServer} UI.
+ *
+ * @author <a href="http://www.vorburger.ch">Michael Vorburger.ch</a>, with Google Gemini Code
+ *     Assist in Agent mode
+ */
+@SpringBootTest
+@AutoConfigureMockMvc
+public class AdkWebServerUITest {
+
+  @Autowired private MockMvc mockMvc;
+
+  @Test
+  public void root_shouldRedirectToDevUi() throws Exception {
+    mockMvc
+        .perform(get("/"))
+        .andExpect(status().is3xxRedirection())
+        .andExpect(redirectedUrl("/dev-ui"));
+  }
+
+  @Test
+  public void devUi_shouldReturnOk() throws Exception {
+    mockMvc.perform(get("/dev-ui")).andExpect(status().isOk());
+  }
+
+  @Test
+  public void devUiWithSlash_shouldReturnOk() throws Exception {
+    mockMvc.perform(get("/dev-ui/")).andExpect(status().isOk());
+  }
+
+  @Test
+  public void nonExistentUiPage_shouldReturnNotFound() throws Exception {
+    mockMvc.perform(get("/non-existent-page")).andExpect(status().isNotFound());
+  }
+}