if len(p) == 0 {
		return 0, r.setErr(nil, false)
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	if err := r.err; err != nil {
		if err == io.EOF {
			err = ErrWriteOnClosed
		}
		return 0, err
	}
	wrote := 0
	for len(p) > 0 {
		n, err = r.write(p)
		wrote += n
		if !r.block || err == nil {
			break
		}
		err = r.setErr(err, true)

    originalSystemErr = System.err

    System.setOut(object : PrintStream(OutputStream.nullOutputStream()) {})
    System.setErr(object : PrintStream(OutputStream.nullOutputStream()) {})
  }

  fun uninstall() {
    originalSystemOut.let {
      System.setOut(it)
    }
    originalSystemErr.let {
      System.setErr(it)
    }
  }

func (s *Scanner) advance(n int) bool {
	if n < 0 {
		s.setErr(ErrNegativeAdvance)
		return false
	}
	if n > s.end-s.start {
		s.setErr(ErrAdvanceTooFar)
		return false
	}
	s.start += n
	return true
}

// setErr records the first error encountered.
func (s *Scanner) setErr(err error) {
	if s.err == nil || s.err == io.EOF {
		s.err = err
	}
}

			if len(expectedOut) == 0 {
				t.Fatal("expected output is empty")
			}

			var out bytes.Buffer
			rootCmd := Cmd(ctx)
			rootCmd.SetArgs(tt.args)
			rootCmd.SetOut(&out)
			rootCmd.SetErr(&out)

			fErr := rootCmd.Execute()
			if fErr != nil {
				t.Fatal(fErr)
			}
			output := out.String()
			if output != expectedOut {
				t.Fatalf("expected %s, got %s", expectedOut, output)
			}

	WantException bool
}

func VerifyOutput(t *testing.T, cmd *cobra.Command, c TestCase) {
	t.Helper()

	cmd.SetArgs(c.Args)

	var out bytes.Buffer
	cmd.SetOut(&out)
	cmd.SetErr(&out)
	cmd.SilenceUsage = true

	fErr := cmd.Execute()
	output := out.String()

	if c.ExpectedOutput != "" && c.ExpectedOutput != output {
		t.Fatalf("Unexpected output for '%s %s'\n got: %q\nwant: %q", cmd.Name(),

	}
}

func verifyExecTestOutput(t *testing.T, cmd *cobra.Command, c execTestCase) {
	t.Helper()

	var out bytes.Buffer
	cmd.SetArgs(c.args)
	cmd.SilenceUsage = true
	cmd.SetOut(&out)
	cmd.SetErr(&out)

	fErr := cmd.Execute()
	output := out.String()

	if c.expectedOutput != "" && c.expectedOutput != output {

	}
}

func verifyExecTestOutput(t *testing.T, cmd *cobra.Command, c execTestCase) {
	t.Helper()

	var out bytes.Buffer
	cmd.SetArgs(c.args)
	cmd.SilenceUsage = true
	cmd.SetOut(&out)
	cmd.SetErr(&out)

	fErr := cmd.Execute()
	output := out.String()

	if c.expectedOutput != "" && c.expectedOutput != output {

		})
	}
}

func verifyExecTestOutput(t *testing.T, cmd *cobra.Command, c execTestCase) {
	t.Helper()

	var out bytes.Buffer
	cmd.SetArgs(c.args)
	cmd.SilenceUsage = true
	cmd.SetOut(&out)
	cmd.SetErr(&out)

	fErr := cmd.Execute()
	output := out.String()

	if c.expectedOutput != "" && c.expectedOutput != output {

	// Save listing...
	go func() {
		if err := saver.saveMetaCacheStream(listCtx, &meta, saveCh); err != nil {
			meta.setErr(err.Error())
		}
		cancel()
	}()

	// Do listing...
	go func(o listPathOptions) {
		err := z.listMerged(listCtx, o, inCh)
		if err != nil {
			meta.setErr(err.Error())
		}
		o.debugln("listAndSave: listing", o.ID, "finished with ", err)
	}(*o)

	cancel context.CancelFunc
}

func (m *metaCacheRPC) setErr(err string) {
	m.mu.Lock()
	defer m.mu.Unlock()
	meta := *m.meta
	if meta.status != scanStateError {
		meta.error = err
		meta.status = scanStateError
	} else {
		// An error is already set.
		return
	}
	meta, _ = m.o.updateMetacacheListing(meta, m.rpc)
	*m.meta = meta
}

// getErr will return an error if the listing failed.