Re: Testing output to STDOUT and STDERR

[Sam Vilain]

On Mon, 09 Feb 2004 14:00, Andy Lester wrote;

  > > While writing tests for some of my code, I was faced with the issue
  > > of capturing what the code sends to STDOUT and STDERR. As I have not
  > > found a module to make it easy, I wrote a trivial code to do it. It
  > > is used like this:
  > I'm not sure what you're actually trying to test.  If you're testing
  > test modules, look at Test::Builder::Tester.

No, something that ties STDOUT so that code can print to it, and you
can test that the right thing was printed; I've had to do this before,
and ended up not going through the CPAN ropes for this module:

{
package Capture;

sub new {
    my $class = shift;
    my $self = { stdout => "" };
    bless $self, $class;
    return $self;
}

sub capture_print {
    my $self = shift;
    $self->{so} = tie(*STDOUT, __PACKAGE__, \$self->{stdout})
        or die "failed to tie STDOUT; $!";
}

sub release_stdout {
    my $self = shift;
    delete $self->{so};
    untie(*STDOUT);
    return $self->{stdout};
}

sub TIEHANDLE {
    my $class = shift;
    my $ref = shift;
    return bless({ stdout => $ref }, $class);
}

sub PRINT {
    my $self = shift;
    ${$self->{stdout}} .= join('', map { defined $_?$_:""} @_); 
}

sub PRINTF {
    my ($self) = shift;
    print STDERR "OUCH @_\n";
    my ($fmt) = shift;
    ${$self->{stdout}} .= sprintf($fmt, @_)
        if (@_);
}

sub glob {
    return \*STDOUT;
}
}

Though, I must say that I prefer his API.  The above was really just a
quick hack based on what I'd extracted out of the ePerl code base.

I'd call it something like IO::Capture if I were to CPAN it.
IO::Seize isn't quite right, but "seize" is definitely a good Perlish
name for the function.

Note that php has a built-in function to do just this.
-- 
Sam Vilain, sam /\T vilain |><>T net, PGP key ID: 0x05B52F13
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