Replace AtomicInteger with int in TestTemplateTestDescriptor.execute()

An atomic integer is not really required to count the invocationIndex.
A local int variable should shuffice. Rewrite using java5 for-each and
while loop instead of lambdas to remove the need for an effectively
final mutable number.

junit-jupiter-engine/src/main/java/org/junit/jupiter/engine/descriptor/TestTemplateTestDescriptor.java

@@ -16,7 +16,6 @@
 import java.lang.reflect.Method;
 import java.util.Iterator;
 import java.util.List;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import org.junit.jupiter.api.extension.ContainerExtensionContext;
 import org.junit.jupiter.api.extension.TestTemplateInvocationContext;
@@ -90,16 +89,17 @@ public JupiterEngineExecutionContext execute(JupiterEngineExecutionContext conte
 		ContainerExtensionContext containerExtensionContext = (ContainerExtensionContext) context.getExtensionContext();
 		List<TestTemplateInvocationContextProvider> providers = validateProviders(containerExtensionContext,
 			context.getExtensionRegistry());
-		AtomicInteger invocationIndex = new AtomicInteger();
-		providers.forEach(provider -> {
+		int invocationIndex = 0;
+		for (TestTemplateInvocationContextProvider provider : providers) {
 			Iterator<TestTemplateInvocationContext> contextIterator = provider.provide(containerExtensionContext);
-			contextIterator.forEachRemaining(invocationContext -> {
-				int index = invocationIndex.incrementAndGet();
+			while (contextIterator.hasNext()) {
+				TestTemplateInvocationContext invocationContext = contextIterator.next();
+				int index = ++invocationIndex;
 				TestDescriptor invocationTestDescriptor = createInvocationTestDescriptor(invocationContext, index);
 				addChild(invocationTestDescriptor);
 				dynamicTestExecutor.execute(invocationTestDescriptor);
-			});
-		});
+			}
+		}
 		validateWasAtLeastInvokedOnce(invocationIndex);
 		return context;
 	}
@@ -126,8 +126,8 @@ private TestDescriptor createInvocationTestDescriptor(TestTemplateInvocationCont
 			invocationContext, index);
 	}
 
-	private void validateWasAtLeastInvokedOnce(AtomicInteger invocationIndex) {
-		if (invocationIndex.get() == 0) {
+	private void validateWasAtLeastInvokedOnce(int invocationIndex) {
+		if (invocationIndex == 0) {
 			throw new TestAbortedException("No supporting "
 					+ TestTemplateInvocationContextProvider.class.getSimpleName() + " provided an invocation context");
 		}