diff --git a/core/lib/Drupal/Core/Test/AssertMailTrait.php b/core/lib/Drupal/Core/Test/AssertMailTrait.php
index 9e60079e12..ed08a187ef 100644
--- a/core/lib/Drupal/Core/Test/AssertMailTrait.php
+++ b/core/lib/Drupal/Core/Test/AssertMailTrait.php
@@ -57,12 +57,15 @@ protected function getMails(array $filter = []) {
    *   this default.
    *
    * @return bool
-   *   TRUE on pass, FALSE on fail.
+   *   TRUE on pass.
    */
   protected function assertMail($name, $value = '', $message = '', $group = 'Email') {
     $captured_emails = $this->container->get('state')->get('system.test_mail_collector') ?: [];
     $email = end($captured_emails);
-    return $this->assertTrue($email && isset($email[$name]) && $email[$name] == $value, $message, $group);
+    $this->assertNotEmpty($email, $message);
+    $this->assertArrayHasKey($name, $email, $message);
+    $this->assertSame($value, $email[$name], $message);
+    return TRUE;
   }
 
   /**
diff --git a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
index 574a1557f7..cc99a7e2a0 100644
--- a/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
+++ b/core/modules/big_pipe/tests/src/Functional/BigPipeTest.php
@@ -268,7 +268,8 @@ public function testBigPipeNoJs() {
     $this->assertNoRaw(BigPipe::STOP_SIGNAL, 'BigPipe stop signal absent.');
 
     // Verifying BigPipe assets are absent.
-    $this->assertTrue(!isset($this->getDrupalSettings()['bigPipePlaceholderIds']) && empty($this->getDrupalSettings()['ajaxPageState']), 'BigPipe drupalSettings and BigPipe asset library absent.');
+    $this->assertArrayNotHasKey('bigPipePlaceholderIds', $this->getDrupalSettings());
+    $this->assertArrayNotHasKey('ajaxPageState', $this->getDrupalSettings());
     $this->assertRaw('</body>', 'Closing body tag present.');
 
     // Verify that 4xx responses work fine. (4xx responses are handled by
diff --git a/core/modules/block/tests/src/Kernel/BlockViewBuilderTest.php b/core/modules/block/tests/src/Kernel/BlockViewBuilderTest.php
index 70d7e1e152..07a1b18cd0 100644
--- a/core/modules/block/tests/src/Kernel/BlockViewBuilderTest.php
+++ b/core/modules/block/tests/src/Kernel/BlockViewBuilderTest.php
@@ -207,7 +207,9 @@ public function testBlockViewBuilderViewAlter() {
     $build = $this->getBlockRenderArray();
     $this->assertFalse(isset($build['#prefix']), 'The appended #pre_render callback has not yet run before rendering.');
     $this->assertIdentical((string) $this->renderer->renderRoot($build), 'Hiya!<br>');
-    $this->assertTrue(isset($build['#prefix']) && $build['#prefix'] === 'Hiya!<br>', 'A cached block without content is altered.');
+    // Check that a cached block without content is altered.
+    $this->assertArrayHasKey('#prefix', $build);
+    $this->assertSame('Hiya!<br>', $build['#prefix']);
   }
 
   /**
diff --git a/core/modules/block_content/tests/src/Kernel/Migrate/d6/MigrateBlockContentTest.php b/core/modules/block_content/tests/src/Kernel/Migrate/d6/MigrateBlockContentTest.php
index b2df21206b..4e9637c107 100644
--- a/core/modules/block_content/tests/src/Kernel/Migrate/d6/MigrateBlockContentTest.php
+++ b/core/modules/block_content/tests/src/Kernel/Migrate/d6/MigrateBlockContentTest.php
@@ -40,14 +40,16 @@ public function testBlockMigration() {
     /** @var \Drupal\block_content\Entity\BlockContent $block */
     $block = BlockContent::load(1);
     $this->assertIdentical('My block 1', $block->label());
-    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
+    $this->assertGreaterThanOrEqual(REQUEST_TIME, $block->getChangedTime());
+    $this->assertLessThanOrEqual(time(), $block->getChangedTime());
     $this->assertIdentical('en', $block->language()->getId());
     $this->assertIdentical('<h3>My first custom block body</h3>', $block->body->value);
     $this->assertIdentical('full_html', $block->body->format);
 
     $block = BlockContent::load(2);
     $this->assertIdentical('My block 2', $block->label());
-    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
+    $this->assertGreaterThanOrEqual(REQUEST_TIME, $block->getChangedTime());
+    $this->assertLessThanOrEqual(time(), $block->getChangedTime());
     $this->assertIdentical('en', $block->language()->getId());
     $this->assertIdentical('<h3>My second custom block body</h3>', $block->body->value);
     $this->assertIdentical('full_html', $block->body->format);
diff --git a/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php b/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
index 2af323a516..bfd03eef24 100644
--- a/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentInterfaceTest.php
@@ -101,8 +101,8 @@ public function testCommentInterface() {
 
     // Test changing the comment author to "Anonymous".
     $comment = $this->postComment(NULL, $comment->comment_body->value, $comment->getSubject(), ['uid' => '']);
-    $this->assertTrue($comment->getAuthorName() == 'Anonymous', 'Comment author successfully changed to anonymous.');
-    $this->assertTrue($comment->getOwnerId() == 0, 'Comment author successfully changed to anonymous.');
+    $this->assertSame('Anonymous', $comment->getAuthorName());
+    $this->assertEquals(0, $comment->getOwnerId());
 
     // Test changing the comment author to an unverified user.
     $random_name = $this->randomMachineName();
@@ -114,7 +114,8 @@ public function testCommentInterface() {
     // Test changing the comment author to a verified user.
     $this->drupalGet('comment/' . $comment->id() . '/edit');
     $comment = $this->postComment(NULL, $comment->comment_body->value, $comment->getSubject(), ['uid' => $this->webUser->getAccountName() . ' (' . $this->webUser->id() . ')']);
-    $this->assertTrue($comment->getAuthorName() == $this->webUser->getAccountName() && $comment->getOwnerId() == $this->webUser->id(), 'Comment author successfully changed to a registered user.');
+    $this->assertSame($this->webUser->getAccountName(), $comment->getAuthorName());
+    $this->assertSame($this->webUser->id(), $comment->getOwnerId());
 
     $this->drupalLogout();
 
diff --git a/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php b/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
index f0fbe3bd8a..0b9bfffca4 100644
--- a/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
+++ b/core/modules/comment/tests/src/Functional/CommentNonNodeTest.php
@@ -176,7 +176,8 @@ public function postComment(EntityInterface $entity, $comment, $subject = '', $c
         $this->assertText($subject, 'Comment subject posted.');
       }
       $this->assertText($comment, 'Comment body posted.');
-      $this->assertTrue((!empty($match) && !empty($match[1])), 'Comment ID found.');
+      // Check the comment ID was extracted.
+      $this->assertArrayHasKey(1, $match);
     }
 
     if (isset($match[1])) {
diff --git a/core/modules/comment/tests/src/Functional/CommentTestBase.php b/core/modules/comment/tests/src/Functional/CommentTestBase.php
index abdae813e0..13b2abdcdc 100644
--- a/core/modules/comment/tests/src/Functional/CommentTestBase.php
+++ b/core/modules/comment/tests/src/Functional/CommentTestBase.php
@@ -175,7 +175,8 @@ public function postComment($entity, $comment, $subject = '', $contact = NULL, $
         $this->assertText($subject, 'Comment subject posted.');
       }
       $this->assertText($comment, 'Comment body posted.');
-      $this->assertTrue((!empty($match) && !empty($match[1])), 'Comment id found.');
+      // Check the comment ID was extracted.
+      $this->assertArrayHasKey(1, $match);
     }
 
     if (isset($match[1])) {
diff --git a/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php b/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
index ea9232f645..ccad0f0775 100644
--- a/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
+++ b/core/modules/config/tests/src/Functional/ConfigInstallProfileOverrideTest.php
@@ -70,8 +70,7 @@ public function testInstallProfileConfigOverwrite() {
 
     $config = $this->config('system.site');
     // Verify the system.site config has a valid UUID.
-    $site_uuid = $config->get('uuid');
-    $this->assertTrue(Uuid::isValid($site_uuid) && strlen($site_uuid) > 0, "Site UUID '$site_uuid' is valid");
+    $this->assertTrue(Uuid::isValid($config->get('uuid')));
     // Verify the profile overrides have been used.
     $this->assertEquals(91, $config->get('weight_select_max'));
     // Ensure the site configure form is used.
diff --git a/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php b/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php
index 27e9cdf192..502a7f0549 100644
--- a/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php
+++ b/core/modules/content_translation/tests/src/Functional/ContentTranslationSettingsTest.php
@@ -148,7 +148,8 @@ public function testSettingsUI() {
     $field_override = BaseFieldOverride::loadByName('entity_test_mul', 'entity_test_mul', 'name');
     $this->assertTrue($field_override->isTranslatable(), 'Base fields can be overridden with a base field bundle override entity.');
     $definitions = $entity_field_manager->getFieldDefinitions('entity_test_mul', 'entity_test_mul');
-    $this->assertTrue($definitions['name']->isTranslatable() && !$definitions['user_id']->isTranslatable(), 'Base field bundle overrides were correctly altered.');
+    $this->assertTrue($definitions['name']->isTranslatable());
+    $this->assertFalse($definitions['user_id']->isTranslatable());
 
     // Test that language settings are correctly stored.
     $language_configuration = ContentLanguageSettings::loadByEntityTypeBundle('comment', 'comment_article');
diff --git a/core/modules/editor/tests/src/Functional/EditorAdminTest.php b/core/modules/editor/tests/src/Functional/EditorAdminTest.php
index e2ffd5ecfb..5f8baf0c94 100644
--- a/core/modules/editor/tests/src/Functional/EditorAdminTest.php
+++ b/core/modules/editor/tests/src/Functional/EditorAdminTest.php
@@ -62,7 +62,8 @@ public function testNoEditorAvailable() {
     $roles_pos = strpos($raw_content, 'Roles');
     $editor_pos = strpos($raw_content, 'Text editor');
     $filters_pos = strpos($raw_content, 'Enabled filters');
-    $this->assertTrue($roles_pos < $editor_pos && $editor_pos < $filters_pos, '"Text Editor" select appears in the correct location of the text format configuration UI.');
+    $this->assertGreaterThan($roles_pos, $editor_pos);
+    $this->assertLessThan($filters_pos, $editor_pos);
 
     // Verify the <select>.
     $select = $this->xpath('//select[@name="editor[editor]"]');
diff --git a/core/modules/field/tests/src/Kernel/BulkDeleteTest.php b/core/modules/field/tests/src/Kernel/BulkDeleteTest.php
index e3743791e4..766d890808 100644
--- a/core/modules/field/tests/src/Kernel/BulkDeleteTest.php
+++ b/core/modules/field/tests/src/Kernel/BulkDeleteTest.php
@@ -266,8 +266,9 @@ public function testPurgeWithDeletedAndActiveField() {
 
     // The field still exists, deleted, with the same field name.
     $fields = \Drupal::entityTypeManager()->getStorage('field_config')->loadByProperties(['uuid' => $deleted_field_uuid, 'include_deleted' => TRUE]);
-    $this->assertTrue(isset($fields[$deleted_field_uuid]) && $fields[$deleted_field_uuid]->isDeleted(), 'The field exists and is deleted');
-    $this->assertTrue(isset($fields[$deleted_field_uuid]) && $fields[$deleted_field_uuid]->getName() == $field_name);
+    $this->assertArrayHasKey($deleted_field_uuid, $fields);
+    $this->assertTrue($fields[$deleted_field_uuid]->isDeleted());
+    $this->assertSame($field_name, $fields[$deleted_field_uuid]->getName());
 
     for ($i = 0; $i < 10; $i++) {
       $entity = $this->container->get('entity_type.manager')
@@ -397,7 +398,8 @@ public function testPurgeFieldStorage() {
 
     // The field still exists, deleted.
     $fields = \Drupal::entityTypeManager()->getStorage('field_config')->loadByProperties(['uuid' => $field->uuid(), 'include_deleted' => TRUE]);
-    $this->assertTrue(isset($fields[$field->uuid()]) && $fields[$field->uuid()]->isDeleted(), 'The field exists and is deleted');
+    $this->assertArrayHasKey($field->uuid(), $fields);
+    $this->assertTrue($fields[$field->uuid()]->isDeleted());
 
     // Purge again to purge the field.
     field_purge_batch(0);
@@ -407,7 +409,8 @@ public function testPurgeFieldStorage() {
     $this->assertCount(0, $fields, 'The field is purged.');
     // The field storage still exists, not deleted.
     $storages = \Drupal::entityTypeManager()->getStorage('field_storage_config')->loadByProperties(['uuid' => $field_storage->uuid(), 'include_deleted' => TRUE]);
-    $this->assertTrue(isset($storages[$field_storage->uuid()]) && !$storages[$field_storage->uuid()]->isDeleted(), 'The field storage exists and is not deleted');
+    $this->assertArrayHasKey($field_storage->uuid(), $storages);
+    $this->assertFalse($storages[$field_storage->uuid()]->isDeleted());
 
     // Delete the second field.
     $bundle = next($this->bundles);
@@ -429,9 +432,11 @@ public function testPurgeFieldStorage() {
 
     // The field and the storage still exist, deleted.
     $fields = \Drupal::entityTypeManager()->getStorage('field_config')->loadByProperties(['uuid' => $field->uuid(), 'include_deleted' => TRUE]);
-    $this->assertTrue(isset($fields[$field->uuid()]) && $fields[$field->uuid()]->isDeleted(), 'The field exists and is deleted');
+    $this->assertArrayHasKey($field->uuid(), $fields);
+    $this->assertTrue($fields[$field->uuid()]->isDeleted());
     $storages = \Drupal::entityTypeManager()->getStorage('field_storage_config')->loadByProperties(['uuid' => $field_storage->uuid(), 'include_deleted' => TRUE]);
-    $this->assertTrue(isset($storages[$field_storage->uuid()]) && $storages[$field_storage->uuid()]->isDeleted(), 'The field storage exists and is deleted');
+    $this->assertArrayHasKey($field_storage->uuid(), $storages);
+    $this->assertTrue($storages[$field_storage->uuid()]->isDeleted());
 
     // Purge again to purge the field and the storage.
     field_purge_batch(0);
diff --git a/core/modules/field/tests/src/Kernel/FieldCrudTest.php b/core/modules/field/tests/src/Kernel/FieldCrudTest.php
index dd40dcff59..46415c731e 100644
--- a/core/modules/field/tests/src/Kernel/FieldCrudTest.php
+++ b/core/modules/field/tests/src/Kernel/FieldCrudTest.php
@@ -284,7 +284,7 @@ public function testDeleteFieldNoData() {
 
     // Test that the first field is not deleted, and then delete it.
     $field = current(\Drupal::entityTypeManager()->getStorage('field_config')->loadByProperties(['entity_type' => 'entity_test', 'field_name' => $this->fieldDefinition['field_name'], 'bundle' => $this->fieldDefinition['bundle'], 'include_deleted' => TRUE]));
-    $this->assertTrue(!empty($field) && empty($field->deleted), 'A new field is not marked for deletion.');
+    $this->assertFalse($field->isDeleted());
     $field->delete();
 
     // Make sure the field was deleted without being marked for purging as there
@@ -298,7 +298,7 @@ public function testDeleteFieldNoData() {
 
     // Make sure the other field is not deleted.
     $another_field = FieldConfig::load('entity_test.' . $another_field_definition['bundle'] . '.' . $another_field_definition['field_name']);
-    $this->assertTrue(!empty($another_field) && !$another_field->isDeleted(), 'A non-deleted field is not marked for deletion.');
+    $this->assertFalse($another_field->isDeleted());
   }
 
   /**
diff --git a/core/modules/field/tests/src/Kernel/FieldStorageCrudTest.php b/core/modules/field/tests/src/Kernel/FieldStorageCrudTest.php
index 362bb85084..dd01b9ab86 100644
--- a/core/modules/field/tests/src/Kernel/FieldStorageCrudTest.php
+++ b/core/modules/field/tests/src/Kernel/FieldStorageCrudTest.php
@@ -319,7 +319,7 @@ public function testDeleteNoData() {
     // Test that the first field is not deleted, and then delete it.
     $field_storage_config_storage = \Drupal::entityTypeManager()->getStorage('field_storage_config');
     $field_storage = current($field_storage_config_storage->loadByProperties(['field_name' => $field_storage_definition['field_name'], 'include_deleted' => TRUE]));
-    $this->assertTrue(!empty($field_storage) && !$field_storage->isDeleted(), 'A new storage is not marked for deletion.');
+    $this->assertFalse($field_storage->isDeleted());
     FieldStorageConfig::loadByName('entity_test', $field_storage_definition['field_name'])->delete();
 
     // Make sure that the field storage is deleted as it had no data.
@@ -341,18 +341,18 @@ public function testDeleteNoData() {
 
     // Make sure the other field and its storage are not deleted.
     $another_field_storage = FieldStorageConfig::load('entity_test.' . $another_field_storage_definition['field_name']);
-    $this->assertTrue(!empty($another_field_storage) && !$another_field_storage->isDeleted(), 'A non-deleted storage is not marked for deletion.');
+    $this->assertFalse($another_field_storage->isDeleted());
     $another_field = FieldConfig::load('entity_test.' . $another_field_definition['bundle'] . '.' . $another_field_definition['field_name']);
-    $this->assertTrue(!empty($another_field) && !$another_field->isDeleted(), 'A field whose storage was not deleted is not marked for deletion.');
+    $this->assertFalse($another_field->isDeleted());
 
     // Try to create a new field the same name as a deleted field and
     // write data into it.
     FieldStorageConfig::create($field_storage_definition)->save();
     FieldConfig::create($field_definition)->save();
     $field_storage = FieldStorageConfig::load('entity_test.' . $field_storage_definition['field_name']);
-    $this->assertTrue(!empty($field_storage) && !$field_storage->isDeleted(), 'A new storage with a previously used name is created.');
+    $this->assertFalse($field_storage->isDeleted());
     $field = FieldConfig::load('entity_test.' . $field_definition['bundle'] . '.' . $field_definition['field_name']);
-    $this->assertTrue(!empty($field) && !$field->isDeleted(), 'A new field for a previously used field name is created.');
+    $this->assertFalse($field->isDeleted());
 
     // Save an entity with data for the field
     $entity = EntityTest::create();
diff --git a/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php b/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php
index 9695cd5769..f306250b48 100644
--- a/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php
+++ b/core/modules/language/tests/src/Functional/LanguageNegotiationContentEntityTest.php
@@ -2,7 +2,6 @@
 
 namespace Drupal\Tests\language\Functional;
 
-use Drupal\Component\Render\FormattableMarkup;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\entity_test\Entity\EntityTest;
 use Drupal\language\Entity\ConfigurableLanguage;
@@ -72,21 +71,24 @@ public function testDefaultConfiguration() {
     $last = $this->container->get('state')->get('language_test.language_negotiation_last');
     $last_content_language = $last[LanguageInterface::TYPE_CONTENT];
     $last_interface_language = $last[LanguageInterface::TYPE_INTERFACE];
-    $this->assertTrue(($last_interface_language == $last_content_language) && ($last_content_language == $translation->language()->getId()), new FormattableMarkup('Interface language %interface_language and Content language %content_language are the same as the translation language %translation_language of the entity.', ['%interface_language' => $last_interface_language, '%content_language' => $last_content_language, '%translation_language' => $translation->language()->getId()]));
+    $this->assertSame($last_content_language, $last_interface_language);
+    $this->assertSame($translation->language()->getId(), $last_content_language);
 
     $translation = $this->entity->getTranslation('es');
     $this->drupalGet($translation->toUrl());
     $last = $this->container->get('state')->get('language_test.language_negotiation_last');
     $last_content_language = $last[LanguageInterface::TYPE_CONTENT];
     $last_interface_language = $last[LanguageInterface::TYPE_INTERFACE];
-    $this->assertTrue(($last_interface_language == $last_content_language) && ($last_content_language == $translation->language()->getId()), new FormattableMarkup('Interface language %interface_language and Content language %content_language are the same as the translation language %translation_language of the entity.', ['%interface_language' => $last_interface_language, '%content_language' => $last_content_language, '%translation_language' => $translation->language()->getId()]));
+    $this->assertSame($last_content_language, $last_interface_language);
+    $this->assertSame($translation->language()->getId(), $last_content_language);
 
     $translation = $this->entity->getTranslation('fr');
     $this->drupalGet($translation->toUrl());
     $last = $this->container->get('state')->get('language_test.language_negotiation_last');
     $last_content_language = $last[LanguageInterface::TYPE_CONTENT];
     $last_interface_language = $last[LanguageInterface::TYPE_INTERFACE];
-    $this->assertTrue(($last_interface_language == $last_content_language) && ($last_content_language == $translation->language()->getId()), new FormattableMarkup('Interface language %interface_language and Content language %content_language are the same as the translation language %translation_language of the entity.', ['%interface_language' => $last_interface_language, '%content_language' => $last_content_language, '%translation_language' => $translation->language()->getId()]));
+    $this->assertSame($last_content_language, $last_interface_language);
+    $this->assertSame($translation->language()->getId(), $last_content_language);
   }
 
   /**
@@ -137,7 +139,11 @@ public function testEnabledLanguageContentNegotiator() {
     $last = $this->container->get('state')->get('language_test.language_negotiation_last');
     $last_content_language = $last[LanguageInterface::TYPE_CONTENT];
     $last_interface_language = $last[LanguageInterface::TYPE_INTERFACE];
-    $this->assertTrue(($last_interface_language == $default_site_langcode) && ($last_interface_language == $last_content_language) && ($last_content_language == $translation->language()->getId()), 'Interface language and Content language are the same as the default translation language of the entity.');
+    // Check that interface language and content language are the same as the
+    // default translation language of the entity.
+    $this->assertSame($default_site_langcode, $last_interface_language);
+    $this->assertSame($last_content_language, $last_interface_language);
+    $this->assertSame($translation->language()->getId(), $last_content_language);
     $this->assertTrue($last_interface_language == $default_site_langcode, 'Interface language did not change from the default site language.');
     $this->assertTrue($last_content_language == $translation->language()->getId(), 'Content language matches the current entity translation language.');
 
diff --git a/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php b/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php
index 2f0edcf43d..36b1405a3f 100644
--- a/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleConfigTranslationTest.php
@@ -139,7 +139,9 @@ public function testConfigTranslation() {
     $string = $this->storage->findString(['source' => 'Medium (220×220)', 'context' => '', 'type' => 'configuration']);
     $this->assertNotEmpty($string, 'Configuration strings have been created upon installation.');
     $locations = $string->getLocations();
-    $this->assertTrue(isset($locations['configuration']) && isset($locations['configuration']['image.style.medium']), 'Configuration string has been created with the right location');
+    // Check the configuration string has been created with the right location.
+    $this->assertArrayHasKey('configuration', $locations);
+    $this->assertArrayHasKey('image.style.medium', $locations['configuration']);
 
     // Check the string is unique and has no translation yet.
     $translations = $this->storage->getTranslations(['language' => $this->langcode, 'type' => 'configuration', 'name' => 'image.style.medium']);
diff --git a/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php b/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php
index 3b40098974..096cac3b2b 100644
--- a/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php
+++ b/core/modules/locale/tests/src/Functional/LocaleJavascriptTranslationTest.php
@@ -103,8 +103,8 @@ public function testFileParsing() {
         $this->assertTrue(isset($source_strings[$str]), new FormattableMarkup('Found source string: %source', $args));
 
         // Make sure that the proper context was matched.
-        $message = $context ? new FormattableMarkup('Context for %source is %context', $args) : new FormattableMarkup('Context for %source is blank', $args);
-        $this->assertTrue(isset($source_strings[$str]) && $source_strings[$str] === $context, $message);
+        $this->assertArrayHasKey($str, $source_strings);
+        $this->assertSame($context, $source_strings[$str]);
       }
 
       $this->assertSame(count($test_strings), count($source_strings), 'Found correct number of source strings.');
diff --git a/core/tests/Drupal/KernelTests/AssertContentTrait.php b/core/tests/Drupal/KernelTests/AssertContentTrait.php
index f459779848..ac4c93b471 100644
--- a/core/tests/Drupal/KernelTests/AssertContentTrait.php
+++ b/core/tests/Drupal/KernelTests/AssertContentTrait.php
@@ -917,7 +917,7 @@ protected function assertThemeOutput($callback, array $variables = [], $expected
    *   this default.
    *
    * @return bool
-   *   TRUE on pass, FALSE on fail.
+   *   TRUE on pass.
    */
   protected function assertFieldsByValue($fields, $value = NULL, $message = '', $group = 'Other') {
     // If value specified then check array for match.
@@ -951,7 +951,9 @@ protected function assertFieldsByValue($fields, $value = NULL, $message = '', $g
         }
       }
     }
-    return $this->assertTrue($fields && $found, $message, $group);
+    $this->assertNotEmpty($fields);
+    $this->assertTrue($found, $message);
+    return TRUE;
   }
 
   /**
@@ -1026,7 +1028,7 @@ protected function getSelectedItem(\SimpleXMLElement $element) {
    *   this default.
    *
    * @return bool
-   *   TRUE on pass, FALSE on fail.
+   *   TRUE on pass.
    */
   protected function assertNoFieldByXPath($xpath, $value = NULL, $message = '', $group = 'Other') {
     $fields = $this->xpath($xpath);
@@ -1043,7 +1045,9 @@ protected function assertNoFieldByXPath($xpath, $value = NULL, $message = '', $g
         }
       }
     }
-    return $this->assertFalse($fields && $found, $message, $group);
+    $this->assertNotEmpty($fields);
+    $this->assertTrue($found, $message);
+    return TRUE;
   }
 
   /**
diff --git a/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php b/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php
index 19c61996de..e7f72e8440 100644
--- a/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Asset/LibraryDiscoveryIntegrationTest.php
@@ -84,7 +84,8 @@ public function testLibrariesOverride() {
     $library = $this->libraryDiscovery->getLibraryByName('core', 'jquery');
     foreach ($library['js'] as $definition) {
       if ($definition['data'] == 'core/modules/system/tests/themes/test_theme/js/collapse.js') {
-        $this->assertTrue($definition['minified'] && $definition['weight'] == -20, 'Previous attributes retained');
+        $this->assertTrue($definition['minified']);
+        $this->assertSame(-20, $definition['weight'], 'Previous attributes retained');
         break;
       }
     }
diff --git a/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php b/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
index c9f3544462..7478840c5d 100644
--- a/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/RendererPlaceholdersTest.php
@@ -1034,12 +1034,13 @@ public function testRenderChildrenPlaceholdersDifferentArguments() {
       ],
     ];
 
+    // Verify that the correct data is cached: the stored #markup is not
+    // affected by placeholder #lazy_builder callbacks.
     $dom = Html::load($cached_element['#markup']);
     $xpath = new \DOMXPath($dom);
-    $parent = $xpath->query('//details/summary[text()="Parent"]')->length;
-    $child = $xpath->query('//details/div[@class="details-wrapper"]/details/summary[text()="Child"]')->length;
-    $subchild = $xpath->query('//details/div[@class="details-wrapper"]/details/div[@class="details-wrapper" and text()="Subchild"]')->length;
-    $this->assertTrue($parent && $child && $subchild, 'The correct data is cached: the stored #markup is not affected by placeholder #lazy_builder callbacks.');
+    $this->assertNotEmpty($xpath->query('//details/summary[text()="Parent"]')->length);
+    $this->assertNotEmpty($xpath->query('//details/div[@class="details-wrapper"]/details/summary[text()="Child"]')->length);
+    $this->assertNotEmpty($xpath->query('//details/div[@class="details-wrapper"]/details/div[@class="details-wrapper" and text()="Subchild"]')->length);
 
     // Remove markup because it's compared above in the xpath.
     unset($cached_element['#markup']);