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Make the RunWrapperTest#externalizableId) test more robust and exercise the property getter.

Co-authored-by: Jesse Glick <[email protected]>

Author: stuartrowe

src/test/java/org/jenkinsci/plugins/workflow/support/steps/build/RunWrapperTest.java

@@ -292,9 +292,9 @@ public void upstreamBuilds() throws Throwable {
     public void externalizableId() throws Throwable {
         sessions.then(j -> {
             WorkflowJob first = j.createProject(WorkflowJob.class, "first-job");
-            first.setDefinition(new CpsFlowDefinition("echo currentBuild.getExternalizableId()\n", true));
+            first.setDefinition(new CpsFlowDefinition("echo(/externalizableId=$currentBuild.externalizableId/)", true));
             WorkflowRun firstRun = j.buildAndAssertSuccess(first);
-            j.assertLogContains(firstRun.getExternalizableId(), firstRun);
+            j.assertLogContains("externalizableId=first-job#1", firstRun);
         });
     }