diff --git a/core/modules/simpletest/src/InstallerTestBase.php b/core/modules/simpletest/src/InstallerTestBase.php
index 57ca485fdb..593f257a4d 100644
--- a/core/modules/simpletest/src/InstallerTestBase.php
+++ b/core/modules/simpletest/src/InstallerTestBase.php
@@ -241,13 +241,16 @@ protected function refreshVariables() {
   /**
    * Continues installation when an expected warning is found.
    *
-   * @param string[] $allowed_warnings
-   *   A list of warning summaries to ignore (e.g. 'PHP', 'PHP OPcode caching',
-   *   etc.).
+   * @param string[] $expected_warnings
+   *   A list of warning summaries to expect on the requirements screen (e.g.
+   *   'PHP', 'PHP OPcode caching', etc.). If only the expected warnings
+   *   are found, the test will click the "continue anyway" link to go to the
+   *   next screen of the installer. If an expected warning is not found, or if
+   *   a warning not in the list is present, a fail is raised.
    */
-  protected function continueOnExpectedWarnings($allowed_warnings = []) {
+  protected function continueOnExpectedWarnings($expected_warnings = []) {
     // Don't try to continue if there are errors.
-    if (strpos($this->getTextContent(), 'Errors found')) {
+    if (strpos($this->getTextContent(), 'Errors found') !== FALSE) {
       return;
     }
     // Allow only details elements that are directly after the warning header
@@ -259,16 +262,17 @@ protected function continueOnExpectedWarnings($allowed_warnings = []) {
     // We add one more selector than expected warnings to confirm that there
     // isn't any other warning before clicking the link.
     $selectors = [];
-    for ($i = 0; $i <= count($allowed_warnings); $i++) {
+    for ($i = 0; $i <= count($expected_warnings); $i++) {
       $selectors[] = 'h3#warning' . implode('', array_fill(0, $i + 1, '+details')) . ' summary';
     }
     $warning_elements = $this->cssSelect(implode(', ', $selectors));
+
     // Confirm that there are only the expected warnings.
     $warnings = [];
     foreach ($warning_elements as $warning) {
       $warnings[] = trim((string) $warning);
     }
-    $this->assertEqual($allowed_warnings, $warnings);
+    $this->assertEqual($expected_warnings, $warnings);
     $this->clickLink('continue anyway');
   }