Use dataprovider for constructor test in ContentEntityTest

Thanks for the patch. Here's some feedback (mostly nitpicks):

1. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -88,155 +88,47 @@ class ContentEntityTest extends KernelTestBase {
   +        'The entity type (node_type) is not supported. The "content_entity" source plugin only supports content entities.',
   

   Nitpick: Add quotes around node_type?

2. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -88,155 +88,47 @@ class ContentEntityTest extends KernelTestBase {
   +        \InvalidArgumentException::class,
   

   Nitpick: Include class to avoid backslash to be consistent with InvalidPluginDefinitionException.

3. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -88,155 +88,47 @@ class ContentEntityTest extends KernelTestBase {
   +        'A bundle was provided but the entity type (user) is not bundleable.',
   

   Nitpick: Add quotes around user?

4. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -88,155 +88,47 @@ class ContentEntityTest extends KernelTestBase {
   +        \InvalidArgumentException::class,
   

   Same as above.

5. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -88,155 +88,47 @@ class ContentEntityTest extends KernelTestBase {
   +        'The provided bundle (foo) is not valid for the (node) entity type.',
   

   Nitpick: Add quotes around foo and node?

6. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
   +   * Setup for the tests.
   

   Nitpick: Since the function is called prepare and there is no longer a setUp function, consider rewording.

7. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
   +  protected function prepare() {
   

   Note: Looking through other code, didn't find any other protected function called prepare except in HtmlRenderer but the other prepare functions were not used for tests. The only other test-related prepare function I saw was in MultilingualReviewPageTestBase which is public. But, since this is for internal processing, protected seems okay.

8. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
   +    );
   +    // Create a term reference field on user.
   

   Nitpick: Add an empty line above comment.

9. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
   @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
   +    // Create some data.
   

   Nitpick: Could use a better comment.

10. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
    @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
    +    $term = Term::create([
    

    Nitpick: Consider adding a comment.

11. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
    @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
    +    $this->anon = User::create([
    

    Unclear where $this->anon is being used.

12. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
    @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
    +    $node = Node::create([
    

    Nitpick: Consider adding a comment.

13. +++ b/core/modules/migrate_drupal/tests/src/Kernel/Plugin/migrate/source/ContentEntityTest.php
    @@ -527,4 +424,102 @@ protected function migrationDefinition($plugin_id, array $configuration = []) {
    +    $this->sourcePluginManager = $this->container->get('plugin.manager.migrate.source');
    

    Nitpick: Consider adding a comment.

Would it be cleaner to break the constructor test out into its own test class, and move prepare() back to setUp()? The constructor test is testing different things to the other test methods.

This makes the conversion simple and straightforward now.

Committed and pushed c14450bc96 to 9.3.x and d6ead31b37 to 9.2.x. Thanks!

Backported to 9.2.x because this is about tests only.