UnitTests - Allow mocking date/time functions in sql

Fixes `Civi\ScheduledCommunications\SendTest::testBirthdayMessage`
by overriding not just date functions in php, but also
in mySql.

When a unit test overrides the system time, this will now
propagate to sql queries as well.

CRM/Core/DAO.php

@@ -525,6 +525,9 @@ public function query($query, $i18nRewrite = TRUE) {
     if ($i18nRewrite and $dbLocale) {
       $query = CRM_Core_I18n_Schema::rewriteQuery($query);
     }
+    if (CIVICRM_UF === 'UnitTests' && CRM_Utils_Time::isOverridden()) {
+      $query = CRM_Utils_Time::rewriteQuery($query);
+    }
 
     $ret = parent::query($query);
 

CRM/Utils/Time.php

@@ -183,6 +183,10 @@ public static function resetTime() {
     self::$callback = NULL;
   }
 
+  public static function isOverridden(): bool {
+    return isset(self::$callback);
+  }
+
   /**
    * Approximate time-comparison. $a and $b are considered equal if they
    * are within $threshold seconds of each other.
@@ -234,4 +238,35 @@ public static function getTimeZoneOffsetFromString(string $timezone) {
     return NULL;
   }
 
+  /**
+   * Rewrite a SQL query to use overridden date/time values for unit tests.
+   *
+   * @param string $query
+   *   The query to rewrite.
+   *
+   * @return string
+   *   The rewritten query with mocked time replacements.
+   */
+  public static function rewriteQuery(string $query): string {
+    // Replace date/time expressions with literal values.
+    $patterns = [
+      '/\bNOW\(\s*\)/' => '"' . self::date('Y-m-d H:i:s') . '"',
+      '/\bCURDATE\(\s*\)/' => '"' . self::date('Y-m-d') . '"',
+      '/\bCURTIME\(\s*\)/' => '"' . self::date('H:i:s') . '"',
+      '/\bCURRENT_DATE\b/' => '"' . self::date('Y-m-d') . '"',
+      '/\bCURRENT_TIME\b/' => '"' . self::date('H:i:s') . '"',
+      '/\bCURRENT_TIMESTAMP\b/' => '"' . self::date('Y-m-d H:i:s') . '"',
+      '/\bSYSDATE\(\)/' => '"' . self::date('Y-m-d H:i:s') . '"',
+      '/\bLOCALTIME\b/' => '"' . self::date('Y-m-d H:i:s') . '"',
+      '/\bLOCALTIMESTAMP\b/' => '"' . self::date('Y-m-d H:i:s') . '"',
+    ];
+
+    // Iterate over the patterns and replace matches in the query.
+    foreach ($patterns as $pattern => $replacement) {
+      $query = preg_replace($pattern, $replacement, $query);
+    }
+
+    return $query;
+  }
+
 }