diff -u b/core/modules/simpletest/src/WebTestBase.php b/core/modules/simpletest/src/WebTestBase.php
--- b/core/modules/simpletest/src/WebTestBase.php
+++ b/core/modules/simpletest/src/WebTestBase.php
@@ -694,9 +694,11 @@
       $parameters = unserialize(urldecode($matches[1]));
       // Handle deprecation notices triggered by system under test.
       if ($parameters[1] === 'User deprecated function') {
-        $message = (string) $parameters[0];
-        if (!in_array($message, DeprecationListener::getSkippedDeprecations())) {
-          call_user_func_array([&$this, 'error'], $parameters);
+        if (getenv('SYMFONY_DEPRECATIONS_HELPER') !== 'disabled') {
+          $message = (string) $parameters[0];
+          if (!in_array($message, DeprecationListener::getSkippedDeprecations())) {
+            call_user_func_array([&$this, 'error'], $parameters);
+          }
         }
       }
       else {
diff -u b/core/phpunit.xml.dist b/core/phpunit.xml.dist
--- b/core/phpunit.xml.dist
+++ b/core/phpunit.xml.dist
@@ -29,6 +29,8 @@
     <env name="SIMPLETEST_DB" value=""/>
     <!-- Example BROWSERTEST_OUTPUT_DIRECTORY value: /path/to/webroot/sites/simpletest/browser_output -->
     <env name="BROWSERTEST_OUTPUT_DIRECTORY" value=""/>
+    <!-- To disable deprecation testing uncomment the next line. -->
+    <!-- <env name="SYMFONY_DEPRECATIONS_HELPER" value="disabled"/> -->
   </php>
   <testsuites>
     <testsuite name="unit">
only in patch2:
unchanged:
--- a/core/scripts/run-tests.sh
+++ b/core/scripts/run-tests.sh
@@ -305,6 +305,10 @@ function simpletest_script_help() {
   --non-html  Removes escaping from output. Useful for reading results on the
               CLI.
 
+  --suppress-deprecations
+
+              Stops tests from failing if deprecation errors are triggered. 
+
   <test1>[,<test2>[,<test3> ...]]
 
               One or more tests to be run. By default, these are interpreted
@@ -369,6 +373,7 @@ function simpletest_script_parse_args() {
     'test_names' => array(),
     'repeat' => 1,
     'die-on-fail' => FALSE,
+    'suppress-deprecations' => FALSE,
     'browser' => FALSE,
     // Used internally.
     'test-id' => 0,
@@ -784,6 +789,12 @@ function simpletest_script_run_one_test($test_id, $test_class) {
       $methods = array();
     }
     $test = new $class_name($test_id);
+    if ($args['suppress-deprecations']) {
+      putenv('SYMFONY_DEPRECATIONS_HELPER=disabled');
+    }
+    else {
+      putenv('SYMFONY_DEPRECATIONS_HELPER=strict');
+    }
     if (is_subclass_of($test_class, TestCase::class)) {
       $status = simpletest_script_run_phpunit($test_id, $test_class);
     }
@@ -834,7 +845,7 @@ function simpletest_script_command($test_id, $test_class) {
   }
   $command .= ' --php ' . escapeshellarg($php);
   $command .= " --test-id $test_id";
-  foreach (array('verbose', 'keep-results', 'color', 'die-on-fail') as $arg) {
+  foreach (array('verbose', 'keep-results', 'color', 'die-on-fail', 'suppress-deprecations') as $arg) {
     if ($args[$arg]) {
       $command .= ' --' . $arg;
     }