Allow tests to expect log messages

_test/core/DokuWikiTest.php

@@ -3,6 +3,8 @@
 use dokuwiki\Extension\PluginController;
 use dokuwiki\Extension\Event;
 use dokuwiki\Extension\EventHandler;
+use dokuwiki\Logger;
+
 /**
  * Helper class to provide basic functionality for tests
  *
@@ -266,4 +268,17 @@ abstract class DokuWikiTest extends PHPUnit\Framework\TestCase {
         $property->setAccessible(true);
         $property->setValue($obj, $value);
     }
+
+    /**
+     * Expect the next log message to contain $message
+     *
+     * @param string $facility
+     * @param string $message
+     * @return void
+     */
+    protected function expectLogMessage(string $message, string $facility = Logger::LOG_ERROR): void
+    {
+        $logger = Logger::getInstance($facility);
+        $logger->expect($message);
+    }
 }

inc/Logger.php

@@ -21,6 +21,9 @@ class Logger
 
     protected $isLogging = true;
 
+    /** @var string[] a list of expected log messages, only used during unit testing */
+    protected $expected = [];
+
     /**
      * Logger constructor.
      *
@@ -165,6 +168,17 @@ class Logger
         return $this->isLogging;
     }
 
+    /**
+     * Tests may register log expectations
+     *
+     * @param string $log
+     * @return void
+     */
+    public function expect($log)
+    {
+        $this->expected[] = $log;
+    }
+
     /**
      * Formats the given data as loglines
      *
@@ -228,10 +242,23 @@ class Logger
     protected function writeLogLines($lines, $logfile)
     {
         if (defined('DOKU_UNITTEST')) {
-            $stderr = fopen('php://stderr', 'w');
-            fwrite($stderr, "\n[" . $this->facility . '] ' . implode("\n", $lines) . "\n");
-            fclose($stderr);
+            // our tests may expect certain log messages
+            if($this->expected) {
+                $expected = array_shift($this->expected);
+                if(!str_contains($lines[0], $expected)) {
+                    throw new \RuntimeException(
+                        "Log expectation failed:\n".
+                        "Expected: $expected\n".
+                        "Actual:   {$lines[0]}"
+                    );
+                }
+            } else {
+                $stderr = fopen('php://stderr', 'w');
+                fwrite($stderr, "\n[" . $this->facility . '] ' . implode("\n", $lines) . "\n");
+                fclose($stderr);
+            }
         }
+
         return io_saveFile($logfile, implode("\n", $lines) . "\n", true);
     }
 }