test: share one Postgres container across test classes

The per-class container was stopped under the Spring context that the next
test class reused, so a second integration test class failed with
"Connection is not available".

src/test/java/core_service/shared/test/AbstractIntegrationTest.java

@@ -5,8 +5,6 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
 import org.springframework.test.context.ActiveProfiles;
 import org.testcontainers.containers.PostgreSQLContainer;
-import org.testcontainers.junit.jupiter.Container;
-import org.testcontainers.junit.jupiter.Testcontainers;
 
 /**
  * Base class for integration tests.
@@ -15,10 +13,14 @@ import org.testcontainers.junit.jupiter.Testcontainers;
 @Tag("IntegrationTest")
 @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
 @ActiveProfiles("dev")
-@Testcontainers
 public abstract class AbstractIntegrationTest {
 
-    @Container
+    // One container per JVM, not per class: Spring caches the context across test classes,
+    // and a per-class container would be stopped under the cached context.
     @ServiceConnection
     static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:17-alpine");
+
+    static {
+        postgres.start();
+    }
 }

src/test/java/core_service/shared/test/AbstractPersistenceTest.java

@@ -5,8 +5,6 @@ import org.springframework.boot.data.jpa.test.autoconfigure.DataJpaTest;
 import org.springframework.boot.jdbc.test.autoconfigure.AutoConfigureTestDatabase;
 import org.springframework.boot.testcontainers.service.connection.ServiceConnection;
 import org.testcontainers.containers.PostgreSQLContainer;
-import org.testcontainers.junit.jupiter.Container;
-import org.testcontainers.junit.jupiter.Testcontainers;
 
 /**
  * Base class for persistence tests.
@@ -15,10 +13,14 @@ import org.testcontainers.junit.jupiter.Testcontainers;
 @Tag("PersistenceTest")
 @DataJpaTest
 @AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
-@Testcontainers
 public abstract class AbstractPersistenceTest {
 
-    @Container
+    // One container per JVM, not per class: Spring caches the context across test classes,
+    // and a per-class container would be stopped under the cached context.
     @ServiceConnection
     static PostgreSQLContainer<?> postgres = new PostgreSQLContainer<>("postgres:17-alpine");
+
+    static {
+        postgres.start();
+    }
 }