MNT Resolve CI problems

- Tell phpcs what to sniff
- Throw a hard error if we can't bootstrap tests correctly
- Force Tokens.php to be run for constant declarations

phpcs.xml.dist

@@ -1,7 +1,10 @@
 <?xml version="1.0"?>
 <ruleset name="PSR12">
- <rule ref="PSR12"/>
- <rule ref="PSR1.Files.SideEffects.FoundWithSymbols">
-    <exclude-pattern>tests/bootstrap\.php</exclude-pattern>
-</rule>
+    <rule ref="PSR12"/>
+    <rule ref="PSR1.Files.SideEffects.FoundWithSymbols">
+        <exclude-pattern>tests/bootstrap\.php</exclude-pattern>
+    </rule>
+
+    <file>./src</file>
+    <file>./tests</file>
 </ruleset>

tests/bootstrap.php

@@ -1,6 +1,9 @@
 <?php
 
 // php_codesniffer autoloader
+
+use PHP_CodeSniffer\Util\Tokens;
+
 $autoloadCandidates = [
     // running from package itself as root
     __DIR__ . '/../vendor/squizlabs/php_codesniffer/autoload.php',
@@ -17,6 +20,15 @@
     }
 }
 
+if (!$autoloaded) {
+    throw new RuntimeException("Couldn't find autoloader");
+}
+
+// Required to correctly run constant definitions in CI, though not needed locally for some reason.
+// Referencing a static property on the Tokens class forces the file containing it to be autoloaded,
+// which results in the constants (defined in the same file) being defined ahead of time.
+Tokens::$operators;
+
 if (!defined('PHP_CODESNIFFER_VERBOSITY')) {
     define('PHP_CODESNIFFER_VERBOSITY', 0);
 }