[R] NextMethod() example from S Programming by Venables and Ripley (page 78)

[blue sky]

S Programming by Venables and Ripley (page 78) has the example listed
at the end of this email. However, I get the following error when I
try the example. I don't understand the descriptions of NextMethod on
its help page. Could somebody let me know how to fix the error of this
example?

> test(x)
c1
c2
Error in NextMethod() : no method to invoke
Calls: test -> test.c1 -> NextMethod -> test.c2 -> NextMethod
Execution halted

####
test=function(x) UseMethod('test')

test.c1=function(x) {
  cat('c1\n')
  NextMethod()
  x
}

test.c2=function(x) {
  cat('c2\n')
  NextMethod()
  x
}

test.c3=function(x) {
  cat('c3\n')
  x
}

x=1
class(x)=c('c1','c2')
test(x)