diff --git a/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php b/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php
index 5b80264681..5912ff048c 100644
--- a/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php
+++ b/core/tests/Drupal/Tests/Traits/PHPUnit8Warnings.php
@@ -23,7 +23,20 @@ trait PHPUnit8Warnings {
    * @var string[]
    */
   private static $ignoredWarnings = [
     'expectExceptionMessageRegExp() is deprecated in PHPUnit 8 and will be removed in PHPUnit 9.',
+    'Using assertContains() with string haystacks is deprecated and will not be supported in PHPUnit 9. Refactor your test to use assertStringContainsString() or assertStringContainsStringIgnoringCase() instead.',
+    'Using assertNotContains() with string haystacks is deprecated and will not be supported in PHPUnit 9. Refactor your test to use assertStringNotContainsString() or assertStringNotContainsStringIgnoringCase() instead.',
+    'assertArraySubset() is deprecated and will be removed in PHPUnit 9.',
+    'assertInternalType() is deprecated and will be removed in PHPUnit 9. Refactor your test to use assertIsArray(), assertIsBool(), assertIsFloat(), assertIsInt(), assertIsNumeric(), assertIsObject(), assertIsResource(), assertIsString(), assertIsScalar(), assertIsCallable(), or assertIsIterable() instead.',
+    'readAttribute() is deprecated and will be removed in PHPUnit 9.',
+    'getObjectAttribute() is deprecated and will be removed in PHPUnit 9.',
+    'The optional $canonicalize parameter of assertEquals() is deprecated and will be removed in PHPUnit 9. Refactor your test to use assertEqualsCanonicalizing() instead.',
+    'assertAttributeEquals() is deprecated and will be removed in PHPUnit 9.',
+    'assertAttributeSame() is deprecated and will be removed in PHPUnit 9.',
+    'assertAttributeInstanceOf() is deprecated and will be removed in PHPUnit 9.',
+    'assertAttributeEmpty() is deprecated and will be removed in PHPUnit 9.',
+    'The optional $ignoreCase parameter of assertContains() is deprecated and will be removed in PHPUnit 9.',
+    'The optional $ignoreCase parameter of assertNotContains() is deprecated and will be removed in PHPUnit 9.',
   ];
 
   /**