Add test coverage for cancellation of external workflow

temporal-sdk/src/test/java/io/temporal/workflow/cancellationTests/ExternalWorkflowCancelTest.java

@@ -0,0 +1,60 @@
+package io.temporal.workflow.cancellationTests;
+
+import static org.junit.Assert.*;
+
+import io.temporal.api.common.v1.WorkflowExecution;
+import io.temporal.client.WorkflowClient;
+import io.temporal.client.WorkflowFailedException;
+import io.temporal.client.WorkflowStub;
+import io.temporal.failure.CanceledFailure;
+import io.temporal.testing.internal.SDKTestWorkflowRule;
+import io.temporal.workflow.ExternalWorkflowStub;
+import io.temporal.workflow.Workflow;
+import io.temporal.workflow.shared.TestWorkflows;
+import org.junit.Rule;
+import org.junit.Test;
+
+public class ExternalWorkflowCancelTest {
+  @Rule
+  public SDKTestWorkflowRule testWorkflowRule =
+      SDKTestWorkflowRule.newBuilder()
+          .setWorkflowTypes(CancellableWorkflowImpl.class, CancelExternalWorkflowImpl.class)
+          .build();
+
+  @Test
+  public void cancelExternalWorkflow() {
+    TestWorkflows.TestWorkflow1 cancellable =
+        testWorkflowRule.newWorkflowStubTimeoutOptions(TestWorkflows.TestWorkflow1.class);
+    WorkflowClient.start(cancellable::execute, "ignored");
+    WorkflowExecution execution = WorkflowStub.fromTyped(cancellable).getExecution();
+
+    TestWorkflows.TestWorkflowStringArg canceler =
+        testWorkflowRule.newWorkflowStubTimeoutOptions(TestWorkflows.TestWorkflowStringArg.class);
+    canceler.execute(execution.getWorkflowId());
+
+    WorkflowStub cancellableStub = WorkflowStub.fromTyped(cancellable);
+    try {
+      cancellableStub.getResult(String.class);
+      fail("unreachable");
+    } catch (WorkflowFailedException e) {
+      assertTrue(e.getCause() instanceof CanceledFailure);
+    }
+  }
+
+  public static class CancellableWorkflowImpl implements TestWorkflows.TestWorkflow1 {
+    @Override
+    public String execute(String input) {
+      Workflow.await(() -> false);
+      return "done";
+    }
+  }
+
+  public static class CancelExternalWorkflowImpl implements TestWorkflows.TestWorkflowStringArg {
+    @Override
+    public void execute(String targetWorkflowId) {
+      TestWorkflows.TestWorkflow1 target =
+          Workflow.newExternalWorkflowStub(TestWorkflows.TestWorkflow1.class, targetWorkflowId);
+      ExternalWorkflowStub.fromTyped(target).cancel();
+    }
+  }
+}