Add boot4-migration module: one Boot 3.5.16 service migrated to 4.1.2, with the real compile, start-up, silent and test failures captured at each step

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_017ic4b4VQVEJWetTT1dYzyJ

boot4-migration/after/src/test/java/com/ankurm/migration/CsrfProbeTest.java

@@ -0,0 +1,24 @@
+package com.ankurm.migration;
+
+import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.httpBasic;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+/** Prints the status of a Basic-authenticated POST without a CSRF token (to compare 3.5 with 4.1). */
+@SpringBootTest(properties = "spring.security.user.password=pw")
+@AutoConfigureMockMvc
+class CsrfProbeTest {
+
+    @Autowired MockMvc mvc;
+
+    @Test
+    void postWithoutCsrfToken() throws Exception {
+        int status = mvc.perform(post("/anything").with(httpBasic("user", "pw"))).andReturn().getResponse().getStatus();
+        System.out.println("CSRFPROBE status=" + status);
+    }
+}

boot4-migration/after/src/test/java/com/ankurm/migration/GreetingControllerTest.java

@@ -0,0 +1,27 @@
+package com.ankurm.migration;
+
+import static org.mockito.BDDMockito.given;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
+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.context.SpringBootTest;
+import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
+import org.springframework.test.context.bean.override.mockito.MockitoBean;
+import org.springframework.test.web.servlet.MockMvc;
+
+@SpringBootTest
+@AutoConfigureMockMvc
+class GreetingControllerTest {
+
+    @Autowired MockMvc mvc;
+    @MockitoBean GreetingService service;
+
+    @Test
+    void greetingUsesService() throws Exception {
+        given(service.title(7)).willReturn("mocked");
+        mvc.perform(get("/greetings/7")).andExpect(status().isOk()).andExpect(jsonPath("$.title").value("mocked"));
+    }
+}

boot4-migration/after/src/test/java/com/ankurm/migration/MockFieldTest.java

@@ -0,0 +1,22 @@
+package com.ankurm.migration;
+
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import org.springframework.boot.test.context.SpringBootTest;
+
+/** Boot 4 fix: Mockito's own extension initialises @Mock fields. */
+@SpringBootTest
+@ExtendWith(MockitoExtension.class)
+class MockFieldTest {
+
+    @Mock Runnable task;
+
+    @Test
+    void mockFieldIsInitialised() {
+        assertNotNull(task, "@Mock field was never initialised");
+    }
+}

boot4-migration/after/src/test/java/com/ankurm/migration/RuntimeFactsTest.java

@@ -0,0 +1,50 @@
+package com.ankurm.migration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.user;
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
+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.context.SpringBootTest;
+import org.springframework.boot.webmvc.test.autoconfigure.AutoConfigureMockMvc;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.test.web.servlet.MockMvc;
+
+/** Pins the runtime behaviour the "breaks at runtime" checklist is about, so a regression fails the build. */
+@SpringBootTest
+@AutoConfigureMockMvc
+class RuntimeFactsTest {
+
+    @Autowired MockMvc mvc;
+    @Autowired JdbcTemplate jdbc;
+
+    @Test
+    void flywayMigrationRan() {
+        assertThat(jdbc.queryForObject("select count(*) from greeting", Integer.class)).isEqualTo(3);
+    }
+
+    @Test
+    void aspectIntercepts() throws Exception {
+        mvc.perform(get("/greetings/1")).andExpect(status().isOk());
+        assertThat(TimingAspect.COUNT.get()).isPositive();
+    }
+
+    @Test
+    void restClientBuilderIsAutoConfigured() throws Exception {
+        mvc.perform(get("/gateway")).andExpect(status().isOk());
+    }
+
+    @Test
+    void metricsEndpointExists() throws Exception {
+        mvc.perform(get("/actuator/metrics").with(user("u")))
+                .andExpect(status().isOk());
+    }
+
+    @Test
+    void serializerIsTheJacksonComponent() throws Exception {
+        mvc.perform(get("/greetings/2")).andExpect(content().json("{\"id\":2,\"title\":\"Hello #2\"}"));
+    }
+}