test(engine): implement test for #9143

engine/pom.xml

@@ -158,6 +158,12 @@
       <scope>test</scope>
     </dependency>
 
+    <dependency>
+      <groupId>org.mockito</groupId>
+      <artifactId>mockito-junit-jupiter</artifactId>
+      <scope>test</scope>
+    </dependency>
+
     <dependency>
       <groupId>org.awaitility</groupId>
       <artifactId>awaitility</artifactId>

engine/src/test/java/io/camunda/zeebe/engine/processing/bpmn/behavior/OutputCollectionBehaviorTest.java

@@ -0,0 +1,103 @@
+/*
+ * Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH under
+ * one or more contributor license agreements. See the NOTICE file distributed
+ * with this work for additional information regarding copyright ownership.
+ * Licensed under the Zeebe Community License 1.1. You may not use this file
+ * except in compliance with the Zeebe Community License 1.1.
+ */
+package io.camunda.zeebe.engine.processing.bpmn.behavior;
+
+import static io.camunda.zeebe.util.buffer.BufferUtil.cloneBuffer;
+import static io.camunda.zeebe.util.buffer.BufferUtil.wrapString;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.anyLong;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import io.camunda.zeebe.el.Expression;
+import io.camunda.zeebe.el.impl.StaticExpression;
+import io.camunda.zeebe.engine.processing.bpmn.BpmnElementContext;
+import io.camunda.zeebe.engine.processing.common.ExpressionProcessor;
+import io.camunda.zeebe.engine.processing.deployment.model.element.ExecutableLoopCharacteristics;
+import io.camunda.zeebe.engine.processing.deployment.model.element.ExecutableMultiInstanceBody;
+import io.camunda.zeebe.msgpack.spec.MsgPackWriter;
+import io.camunda.zeebe.util.Either;
+import java.util.Optional;
+import org.agrona.DirectBuffer;
+import org.agrona.ExpandableArrayBuffer;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Answers;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+public class OutputCollectionBehaviorTest {
+
+  @Test // regression test for #9143
+  void shouldRaiseIncidentWhenOverwritingOutputCollectionWithLessElements() {
+    // given
+    final var collectionWithSize1 = createCollection(1);
+    final var elementToAdd = wrapString("element to add");
+    final var indexThatIsOutOfBounds = 2;
+    final var outputElementsExpression = new StaticExpression("OUTPUT_COLLECTION");
+    final var outputElementName = wrapString("OUTPUT_ELEMENT");
+    final var loopCharacteristics =
+        createLoopCharacteristics(outputElementName, outputElementsExpression);
+
+    final var mockStateBehavior = mock(BpmnStateBehavior.class, Answers.RETURNS_DEEP_STUBS);
+    when(mockStateBehavior.getLocalVariable(any(), eq(outputElementName)))
+        .thenReturn(collectionWithSize1);
+
+    final var mockExpressionProcessor = mock(ExpressionProcessor.class);
+    when(mockExpressionProcessor.evaluateAnyExpression(eq(outputElementsExpression), anyLong()))
+        .thenReturn(Either.right(elementToAdd));
+
+    final var mockElement = mock(ExecutableMultiInstanceBody.class);
+    when(mockElement.getLoopCharacteristics()).thenReturn(loopCharacteristics);
+
+    final var mockChildContext = mock(BpmnElementContext.class);
+    when(mockStateBehavior.getElementInstance(mockChildContext).getMultiInstanceLoopCounter())
+        .thenReturn(indexThatIsOutOfBounds);
+
+    final var sut = new OutputCollectionBehavior(mockStateBehavior, mockExpressionProcessor);
+
+    // when
+    final var result = sut.updateOutputCollection(mockElement, mockChildContext, null);
+
+    // then
+    assertThat(result.isLeft()).isTrue();
+
+    // final var failure = result.getLeft();
+    // TODO ass assertions on failure
+  }
+
+  private ExecutableLoopCharacteristics createLoopCharacteristics(
+      final DirectBuffer outputElementName, final Expression outputElementExpression) {
+    return new ExecutableLoopCharacteristics(
+        false,
+        Optional.empty(),
+        null,
+        Optional.empty(),
+        Optional.of(outputElementName),
+        Optional.of(outputElementExpression));
+  }
+
+  private DirectBuffer createCollection(final int size) {
+    final var writer = new MsgPackWriter();
+    final var buffer = new ExpandableArrayBuffer();
+
+    writer.wrap(buffer, 0);
+
+    // initialize the array with nil
+    writer.writeArrayHeader(size);
+    for (var i = 0; i < size; i++) {
+      writer.writeNil();
+    }
+
+    final var length = writer.getOffset();
+
+    return cloneBuffer(buffer, 0, length);
+  }
+}

engine/src/test/resources/mockito-extensions/org.mockito.plugins.MockMaker

@@ -0,0 +1 @@
+mock-maker-inline