if n, err := b.Read(nil); n != 0 || err != nil {
		t.Fatalf("Read(nil) = %d,%v; want 0,nil", n, err)
	}
	if err := b.UnreadByte(); err == nil {
		t.Fatal("UnreadByte after Read(nil): got no error")
	}

	// after successful read
	if _, err := b.ReadBytes('m'); err != nil {
		t.Fatalf("ReadBytes: %v", err)
	}
	if err := b.UnreadByte(); err != nil {
		t.Fatalf("UnreadByte: %v", err)
	}
	c, err := b.ReadByte()

	}
	r, err := NewReader(bytes.NewReader(data), int64(len(data)))
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	for _, f := range r.File {
		r, err := f.Open()
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
		if _, err := io.Copy(io.Discard, r); err != nil {
			t.Fatalf("unexpected error: %v", err)
		}
	}
}

func TestBaseOffsetPlusOverflow(t *testing.T) {

		})
		if err != nil {
			log.Fatal(err)
		}
		if _, err := w.Write(data); err != nil {
			log.Fatal(err)
		}
		seen[name] = true
		return nil
	})
	if err != nil {
		log.Fatal(err)
	}
	if err := zw.Close(); err != nil {
		log.Fatal(err)
	}
	if len(seen) == 0 {
		log.Fatalf("did not find any files to add")
	}
	if !seen["US/Eastern"] {
		log.Fatalf("did not find US/Eastern to add")
	}

		})
		if err != nil {
			t.Fatalf("creating file %d: %v", i, err)
		}
	}
	if err := w.Close(); err != nil {
		t.Fatalf("Writer.Close: %v", err)
	}
	s := buf.String()
	zr, err := NewReader(strings.NewReader(s), int64(len(s)))
	if err != nil {
		t.Fatalf("NewReader: %v", err)
	}
	if got := len(zr.File); got != nFiles {
		t.Fatalf("File contains %d files, want %d", got, nFiles)
	}

		if err := tw.WriteHeader(hdr); err != nil {
			t.Fatalf("WriteHeader() = %v, want nil", err)
		}
		if err := tw.Close(); err != nil {
			t.Fatalf("Close() = %v, want nil", err)
		}
		if _, err := tw.Write([]byte("Kilts")); err != ErrWriteAfterClose {
			t.Fatalf("Write() = %v, want %v", err, ErrWriteAfterClose)
		}
		if err := tw.Flush(); err != ErrWriteAfterClose {
			t.Fatalf("Flush() = %v, want %v", err, ErrWriteAfterClose)
		}

	}
	if err := tw.WriteHeader(hdr); err != nil {
		t.Fatalf("tw.WriteHeader: %v", err)
	}
	if _, err := tw.Write(data); err != nil {
		t.Fatalf("tw.Write: %v", err)
	}
	if err := tw.Close(); err != nil {
		t.Fatalf("tw.Close: %v", err)
	}

	// Read it back.
	tr := NewReader(&b)
	rHdr, err := tr.Next()
	if err != nil {
		t.Fatalf("tr.Next: %v", err)
	}
	if !reflect.DeepEqual(rHdr, hdr) {

func (w *Walker) pushScope(name string) (popFunc func()) {
	w.scope = append(w.scope, name)
	return func() {
		if len(w.scope) == 0 {
			log.Fatalf("attempt to leave scope %q with empty scope list", name)
		}
		if w.scope[len(w.scope)-1] != name {
			log.Fatalf("attempt to leave scope %q, but scope is currently %#v", name, w.scope)
		}
		w.scope = w.scope[:len(w.scope)-1]
	}
}

The [SetCrashOutput] function allows the user to specify an alternate
file to which the runtime should write its fatal crash report.
It may be used to construct an automated reporting mechanism for all
unexpected crashes, not just those in goroutines that explicitly use