Split assertTrue using && into multiple assertions

core/modules/comment/tests/src/Functional/CommentEntityTest.php:89:
    $this->assertFalse(isset($settings['ajaxPageState']['libraries']) && in_array('comment/drupal.comment-new-indicator', explode(',', $settings['ajaxPageState']['libraries'])), 'drupal.comment-new-indicator library is present.');
    $this->assertFalse(isset($settings['history']['lastReadTimestamps']) && in_array($term->id(), array_keys($settings['history']['lastReadTimestamps'])), 'history.lastReadTimestamps is present.');

Not sure what the intent of this is, as neither ajaxPageState nor history seem to be set, never mind the child items or the part after &&, so this is largely useless.

Work in progress, there are many more to do.

Thanks for picking this up, I assume you're happy with what I did in #3 except for the test fails, then I can RTBC this once the review issues are fixed.

1. +++ b/core/modules/search/tests/src/Functional/SearchAdvancedSearchFormTest.php
   @@ -101,12 +101,10 @@ public function testFormRefill() {
   -        $elements = $this->xpath('//input[@name=:name]', [':name' => $key]);
   -        $this->assertTrue(isset($elements[0]) && $elements[0]->getValue() == $value, "Field $key is set to $value");
   +        $this->assertSession()->fieldValueEquals($key, $value);
          }
          else {
   -        $elements = $this->xpath('//input[@name=:name]', [':name' => $key]);
   -        $this->assertTrue(isset($elements[0]) && !empty($elements[0]->getAttribute('checked')), "Field $key is checked");
   +        $this->assertSession()->checkboxChecked($key);
   

   So much nicer!

2. +++ b/core/tests/Drupal/KernelTests/Core/Cache/GenericCacheBackendUnitTestBase.php
   @@ -138,7 +138,8 @@ public function testSetGet() {
   -    $this->assertTrue($cached->created >= REQUEST_TIME && $cached->created <= round(microtime(TRUE), 3), 'Created time is correct.');
   +    $this->assertLessThanOrEqual($cached->created, REQUEST_TIME);
   +    $this->assertGreaterThanOrEqual($cached->created, round(microtime(TRUE), 3));
   

   I think $expected and $actual are the wrong way round here (and therefore LessThan should be GreaterThan and vice versa), same for a number of other instances in this file.

I read through all changes in the patch and only have one comment that doesn't need changes, and one question:

1. +++ b/core/modules/field/tests/src/Kernel/BulkDeleteTest.php
   @@ -397,7 +398,8 @@ public function testPurgeFieldStorage() {
   +    $this->assertArrayHasKey($field->uuid(), $fields);
   +    $this->assertTrue($fields[$field->uuid()]->isDeleted());
   

   I do wonder if it's overkill asserting that the key exists first, as the second line will fail anyway with an error if the key isn't set. I guess really it doesn't matter though, this and similar instances can be left as-is.

2. +++ b/core/modules/locale/tests/src/Functional/LocaleTranslationUiTest.php
   @@ -141,13 +141,15 @@ public function testStringTranslation() {
   -    $this->assertTrue($name != $translation && t($name, [], ['langcode' => $langcode]) == $translation, 't() works for non-English.');
   +    $this->assertNotEquals($name, $translation);
   +    $this->assertEquals(t($name, [], ['langcode' => $langcode]), $translation, 't() works for non-English.');
   ...
   -    $this->assertTrue($name != $translation_to_en && t($name, [], ['langcode' => 'en']) == $translation_to_en, 't() works for English.');
   +    $this->assertNotEquals($name, $translation_to_en);
   +    $this->assertEquals(t($name, [], ['langcode' => 'en']), $translation_to_en, 't() works for English.');
   

   I think $expected and $actual are the wrong way round here?

Otherwise I think this is good to go.

Looks perfect now - RTBC assuming testbot agrees.