Add unit tests for complex deep array merge cases

patch applied cleanly for 8.x

+++ b/core/modules/system/lib/Drupal/system/Tests/Bootstrap/DeepMergeUnitTest.php
@@ -0,0 +1,112 @@
+class DeepMergeUnitTest extends UnitTestBase {

This isn't a phpunit unit test but a simpletest unit test. Note: \Drupal\Tests\Component\Utility\NestedArrayTest. seem to cover that function already. Maybe you have some more cases than that file?

So yeah this is probably a won't fix, unless someone reopens it.

You totally should.

Thank you for that last bit.

You actually need the :: with @covers or it does not work. Running a coverage test without it will fail the whole test.

I also switched assertEquals to assertSame since the latter uses strict comparisons.
And unlike simpletest, the assertTrue/assertFalse also use strict comparisons.

Also unlike simpletest, assertSame specifies the params as assertSame($expected, $actual, $message = ''), so I switched the order on some of the assertions that were backwards. This is useful when running tests in PHPStorm for example, because it will show you a comparison between expected and actual

The rest was just fixing doxygen stuff.

EDIT: Ah! I didn't read the actual patch past the missing ::, and I just fixed the file after applying the patch locally. So I touched a bit more than the previous patches did, and many of the things I mentioned above were pre-existing, my apologies :(

13: nested-array-test-1696172-13.patch queued for re-testing.

Random fail.

Committed 2826a61 and pushed to 8.x. Thanks!

diff --git a/core/tests/Drupal/Tests/Component/Utility/NestedArrayTest.php b/core/tests/Drupal/Tests/Component/Utility/NestedArrayTest.php
index 49dc874..08c9f78 100644
--- a/core/tests/Drupal/Tests/Component/Utility/NestedArrayTest.php
+++ b/core/tests/Drupal/Tests/Component/Utility/NestedArrayTest.php
@@ -90,7 +90,7 @@ public function testGetValue() {
   }
 
   /**
-   * Tests setting nested array values:
+   * Tests setting nested array values.
    *
    * @covers ::setValue
    */

Fixed during commit.