A test suite says what it checks; coverage says what it reaches. With coverage on, every local request notes which templates it read, which of their tags ran, and which branch each {if} and {case} took. The report then shows each template with the parts that never ran marked.

<?php

  $template = "{if \$stock gt 0}In stock{else}Sold out{/if}";
  $items    = padCoverageMark ( padCoverageItems ( $template ), [], [ 'if $stock gt 0' => [ 'if' => 12 ] ] );
  $marked   = padCoverageHtml ( $template, $items );

?>

{!marked}

{if $stock gt 0}In stock{else}Sold out{/if}

• $padCoverage = TRUE in _config/config.php records into the run default; a name instead of TRUE records into a run of that name, and ?page&padCoverage=name records one request.
• develop/?coverage&start=suites records every local request of every application until develop/?coverage&stop - start it, run the suites, stop it, and develop/?coverage&run=suites lists every template with the share of its tags and branches that ran, and the files no request read at all.
• A run is a file of JSON lines, DATA/coverage/<run>.jsonl, one line per request. Only local requests are recorded.
• An {if} without an {else} has one branch more: the run in which its condition was false. It is marked on the {/if}.