add phpunit markup script

Author: simonLeary42

CONTRIBUTING.md

@@ -109,6 +109,8 @@ $ docker exec -it "$container" bash
 
 For `/path/to/tests/`, you usually want `./test/functional/` but you can select a specific file to save time when troubleshooting specific tests.
 
+Note: To enhance the stack traces in `phpunit`'s output, pipe the output to `./test/phpunit-markup.php`.
+
 ### code coverage
 
 `phpunit` has code coverage built in.

test/phpunit-markup.php

@@ -0,0 +1,11 @@
+#!/usr/bin/env php
+<?php while ($line = fgets(STDIN)) {
+    $line = rtrim($line, "\n");
+    if (preg_match('/\s*^(\/.*):(\d+)$/', $line, $matches)) {
+        [$path, $lineNumber] = [$matches[1], intval($matches[2]) - 1];
+        $src_line = trim(file($path)[$lineNumber]);
+        echo "$line \033[36m$src_line\033[0m\n";
+    } else {
+        echo "$line\n";
+    }
+}