Test::Class would be one solution. Something like this should do the job (untested code):

{
    package BlahBlah::Test;
    use base qw(Test::Class);
    
    sub test_object_emit {
        my ($self, $test_object, $emit_method) = @_;
        my $ot = output_test->new( $self->current_method );
        my $outfile = $ot->openout();
        $test_object->$emit_method($outfile);
        $ot->ok_files_match();
    };

    sub out1 : Test(tests => 4) {
        my $self = shift;
        my $x = new BlahBlah
        $x->foo(5000);
        $x->bar(200);
        $self->test_object_emit($x, "emit");
    };

    sub out2 : Test(tests => 4) {
        my $self = shift;
        my $x = new Fribble
        $x->ni(12);
        $self->test_object_emit($x, "super_emit");
    };
    
    # ... etc ...
        
};

BlahBlah::Test->runtests;
[download]

We name our test methods after each output_test. Since $self->current_method returns the name of the running test method we can use this to create the appropriate output_test object in test_object_emit.

It you die in a Test::Class test method the remaining tests in that method are automatically failed. So if anything in test_object_emit dies all the tests in the calling test method will fail, and you'll go on to the next test case (aka method).

I'm assuming that ok_files_match runs four tests (hence the tests => 4).