#summary The principles of Test::Builder and Test::More.

= Introduction =

Some core principles guiding the development of Test::Builder and Test::More.

=== Non-Interference ===

Code should work just the same in a test script as in a normal script.

For example, you might be tempted to write a test routine which uses the & prototype to accept a "block" that's really a subroutine reference.

{{{
sub run (&) {
    my $code = shift;
    $code->();
}

run {
    ...test code...
};
}}}

The fact that it's not really a block can be seen by anything which uses `caller()`.  Consider testing Carp.  To complete the encapsulation you have to trick `caller()` by using something like `Sub::Uplevel`.