Ported TestInstance.Lifecycle.PER_CLASS fix to 4.x (#5052)

microprofile/tests/junit5/src/main/java/io/helidon/microprofile/tests/junit5/HelidonJunitExtension.java

@@ -55,6 +55,7 @@
 import org.eclipse.microprofile.config.spi.ConfigProviderResolver;
 import org.eclipse.microprofile.config.spi.ConfigSource;
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
 import org.junit.jupiter.api.extension.AfterAllCallback;
 import org.junit.jupiter.api.extension.AfterEachCallback;
 import org.junit.jupiter.api.extension.BeforeAllCallback;
@@ -363,6 +364,14 @@ public <T> T interceptTestClassConstructor(Invocation<T> invocation,
         // we need to start container before the test class is instantiated, to honor @BeforeAll that
         // creates a custom MP config
         if (container == null) {
+            // at this early stage the class should be checked whether it is annotated with
+            // @TestInstance(TestInstance.Lifecycle.PER_CLASS) to start correctly the container
+            TestInstance testClassAnnotation = testClass.getAnnotation(TestInstance.class);
+            if (testClassAnnotation != null && testClassAnnotation.value().equals(TestInstance.Lifecycle.PER_CLASS)){
+                throw new RuntimeException("When a class is annotated with @HelidonTest, "
+                        + "it is not compatible with @TestInstance(TestInstance.Lifecycle.PER_CLASS)"
+                        + "annotation, as it is a Singleton CDI Bean.");
+            }
             startContainer(classLevelBeans, classLevelExtensions, classLevelDisableDiscovery);
         }