### Question:
PackagedProgram { public String getPreviewPlan() throws ProgramInvocationException { Thread.currentThread().setContextClassLoader(this.getUserCodeClassLoader()); List<DataSinkNode> previewPlan; if (isUsingProgramEntryPoint()) { previewPlan = Optimizer.createPreOptimizedPlan(getPlan()); } else if (isUsingInteractiveMode()) { PreviewPlanEnvironment env = new PreviewPlanEnvironment(); env.setAsContext(); try { invokeInteractiveModeForExecution(); } catch (ProgramInvocationException e) { throw e; } catch (Throwable t) { if (env.previewPlan == null) { if (env.preview != null) { return env.preview; } else { throw new ProgramInvocationException("The program caused an error: ", getPlan().getJobId(), t); } } } finally { env.unsetAsContext(); } if (env.previewPlan != null) { previewPlan = env.previewPlan; } else { throw new ProgramInvocationException( "The program plan could not be fetched. The program silently swallowed the control flow exceptions.", getPlan().getJobId()); } } else { throw new RuntimeException(); } PlanJSONDumpGenerator jsonGen = new PlanJSONDumpGenerator(); StringWriter string = new StringWriter(1024); try (PrintWriter pw = new PrintWriter(string)) { jsonGen.dumpPactPlanAsJSON(previewPlan, pw); } return string.toString(); } PackagedProgram(File jarFile, String... args);  PackagedProgram(File jarFile, List<URL> classpaths, String... args);  PackagedProgram(File jarFile, @Nullable String entryPointClassName, String... args);  PackagedProgram(File jarFile, List<URL> classpaths, @Nullable String entryPointClassName, String... args);  PackagedProgram(Class<?> entryPointClass, String... args); void setSavepointRestoreSettings(SavepointRestoreSettings savepointSettings); SavepointRestoreSettings getSavepointSettings(); String[] getArguments(); String getMainClassName(); boolean isUsingInteractiveMode(); boolean isUsingProgramEntryPoint(); JobWithJars getPlanWithoutJars(); JobWithJars getPlanWithJars(); String getPreviewPlan(); @Nullable String getDescription(); void invokeInteractiveModeForExecution(); List<URL> getClasspaths(); ClassLoader getUserCodeClassLoader(); List<URL> getAllLibraries(); void deleteExtractedLibraries(); static List<File> extractContainedLibraries(URL jarFile); static void deleteExtractedLibraries(List<File> tempLibraries); static final String MANIFEST_ATTRIBUTE_ASSEMBLER_CLASS; static final String MANIFEST_ATTRIBUTE_MAIN_CLASS; }### Answer:
@Test public void testGetPreviewPlan() { try { PackagedProgram prog = new PackagedProgram(new File(CliFrontendTestUtils.getTestJarPath())); final PrintStream out = System.out; final PrintStream err = System.err; try { System.setOut(new PrintStream(new NullOutputStream())); System.setErr(new PrintStream(new NullOutputStream())); Assert.assertNotNull(prog.getPreviewPlan()); } finally { System.setOut(out); System.setErr(err); } } catch (Exception e) { System.err.println(e.getMessage()); e.printStackTrace(); Assert.fail("Test is erroneous: " + e.getMessage()); } }