anchor.diff:  
   [source,java]
   ----
  -StringWriter sw = new StringWriter();
   MyApp app = new MyApp();
   CommandLine cmd = new CommandLine(app);
  +
  +StringWriter sw = new StringWriter();
   cmd.setOut(new PrintWriter(sw));
   
   // black box testing
  
positive.code: //import org.junit.Before; // JUnit 4
  import org.junit.jupiter.api.AfterEach;  // JUnit 5
  import org.junit.jupiter.api.BeforeEach; // JUnit 5
  
  final PrintStream originalOut = System.out;
  final PrintStream originalErr = System.err;
  final ByteArrayOutputStream out = new ByteArrayOutputStream();
  final ByteArrayOutputStream err = new ByteArrayOutputStream();
  
  //@Before   // JUnit 4
  @BeforeEach // JUnit 5
  public void setUpStreams() {
      out.reset();
      err.reset();
      System.setOut(new PrintStream(out));
      System.setErr(new PrintStream(err));
  }
  
  //@After   // JUnit 4
  @AfterEach // JUnit 5
  public void restoreStreams() {
      System.setOut(originalOut);
      System.setErr(originalErr);
  }
  
  @Test
  public void test() {
      String[] args = "my command args".split(" ");
      new CommandLine(new MyApp()).execute(args);
      assertEquals("MY COMMAND OUTPUT", out.toString());
      assertEquals("", err.toString());
  }
  ----
  
  
negative.code: 
      public void run() {
          // make testing easier by printing to the Err and Out streams provided by picocli
          spec.commandLine().getOut().println("Your output is abc...");
      }
  }
  ----
  