UuidItem should implement generateSampleValue

Thank you, the patch is perfect!

We now need to add a test that this works properly. I found \Drupal\Tests\field\Kernel\String\UuidFormatterTest which you could use as inspiration for a new UuidItemTest with a testRandomValue() method.

The test looks great, very nice. And quite impressive if that's your first test!!! Nice work, @faline

Some notes:

1. +++ b/core/modules/field/tests/src/Kernel/String/UuidItemTest.php
   @@ -0,0 +1,29 @@
   + * Tests the values of a UUID field.
   

   I think we should just say "Tests the UUID field." so it still makes sense when we add some more tests to this at some point.

2. +++ b/core/modules/field/tests/src/Kernel/String/UuidItemTest.php
   @@ -0,0 +1,29 @@
   +   * Tests 'uuid' random values.
   ...
   +  public function testUuidRandomValue() {
   

   I know I suggested this method name, so this is my fault, but the method we are testing is generateSampleValue() so I think the test method should be testSampleValue() (I think we can leave the UUID part out of the method name as that is in the class name).

3. +++ b/core/modules/field/tests/src/Kernel/String/UuidItemTest.php
   @@ -0,0 +1,29 @@
   +    $this->entityValidateAndSave($entity);
   

   I think we shouldn't really care about saving the entity. I think

   $this->assertTrue(\Drupal::service('uuid')->isValid($uuid_field->value));
   

   or something like that would be a more precise assertion for what we are testing here.

Perfect, the test looks great.

In the future it would be nice if you could generate an interdiff along with your patch, so it is visible what changed between two patches. See https://www.drupal.org/documentation/git/interdiff for more information. In this case it's not that big of a deal, because the patch is pretty small, but it's considered a best practice to always provide one.

I have one super minor quibble:

+++ b/core/modules/field/tests/src/Kernel/String/UuidItemTest.php
@@ -0,0 +1,30 @@
+     $this->assertTrue(Uuid::isValid($uuid_field->value));

This line is not indented correctly.

Also, it would be awesome if you could upload a "tests-only" patch, i.e. a patch file that only contains the added test. This will fail, but that will prove that your test actually tests what we want it to.

Thanks!

That's absolutely perfect. Thank you for your persistence!