diff --git a/src/CachePoolTest.php b/src/CachePoolTest.php
index 217a2f8..15b121e 100644
--- a/src/CachePoolTest.php
+++ b/src/CachePoolTest.php
@@ -34,6 +34,16 @@ abstract class CachePoolTest extends TestCase
      */
     abstract public function createCachePool(): CacheItemPoolInterface;
 
+    /**
+     * A second pool backed by the same storage as createCachePool(), under a different namespace.
+     *
+     * Return null when the implementation cannot provide one, the test is then skipped.
+     */
+    public function createCachePoolWithOtherNamespace(): ?CacheItemPoolInterface
+    {
+        return null;
+    }
+
     #[Before]
     public function setupService()
     {
@@ -318,6 +328,34 @@ public function testClearWithDeferredItems()
         $this->assertFalse($this->cache->getItem('key')->isHit(), 'Deferred items must be cleared on clear(). ');
     }
 
+    public function testClearDoesNotAffectOtherNamespaces()
+    {
+        if (isset($this->skippedTests[__FUNCTION__])) {
+            $this->markTestSkipped($this->skippedTests[__FUNCTION__]);
+        }
+
+        $other = $this->createCachePoolWithOtherNamespace();
+
+        if (null === $other) {
+            $this->markTestSkipped('This implementation cannot provide a second pool on the same storage with another namespace.');
+        }
+
+        try {
+            $this->cache->save($this->cache->getItem('key')->set('value'));
+            $other->save($other->getItem('key')->set('other value'));
+
+            $this->assertTrue($this->cache->clear(), 'clear() must return true if cache was cleared. ');
+            $this->assertFalse($this->cache->hasItem('key'), 'The cleared pool should be empty after it is cleared.');
+
+            $otherItem = $other->getItem('key');
+            $this->assertTrue($otherItem->isHit(), 'Clearing a pool must not clear a pool using another namespace on the same storage.');
+            $this->assertSame('other value', $otherItem->get(), 'The item stored in the other namespace must keep its own value.');
+        } finally {
+            // The tearDownService() hook only clears $this->cache, so the other pool is cleared here.
+            $other->clear();
+        }
+    }
+
     public function testDeleteItem()
     {
         if (isset($this->skippedTests[__FUNCTION__])) {
diff --git a/src/TaggableCachePoolTest.php b/src/TaggableCachePoolTest.php
index 3e9216e..a82e8f7 100644
--- a/src/TaggableCachePoolTest.php
+++ b/src/TaggableCachePoolTest.php
@@ -34,6 +34,16 @@ abstract class TaggableCachePoolTest extends TestCase
      */
     abstract public function createCachePool(): TaggableCacheItemPoolInterface;
 
+    /**
+     * A second pool backed by the same storage as createCachePool(), under a different namespace.
+     *
+     * Return null when the implementation cannot provide one, the test is then skipped.
+     */
+    public function createCachePoolWithOtherNamespace(): ?TaggableCacheItemPoolInterface
+    {
+        return null;
+    }
+
     #[Before]
     public function setupService()
     {
@@ -221,7 +231,7 @@ public function testRemoveTagWhenItemIsRemoved()
 
         // Save the item and then delete it
         $this->cache->save($item);
-        $this->cache->deleteItem('key');
+        $this->assertTrue($this->cache->deleteItem('key'), 'deleteItem() must return true when a tagged item is deleted');
 
         // Create a new item (same key) (no tags)
         $item = $this->cache->getItem('key')->set('value');
@@ -286,16 +296,28 @@ public function testInvalidateTags()
             $this->markTestSkipped($this->skippedTests[__FUNCTION__]);
         }
 
+        // Matched through both invalidated tags at once.
         $item = $this->cache->getItem('key')->set('value');
         $item->setTags(['tag1', 'tag2']);
         $this->cache->save($item);
+        // Matched through tag2 only, so tag2 must be handled on its own.
         $item = $this->cache->getItem('key2')->set('value');
+        $item->setTags(['tag2']);
+        $this->cache->save($item);
+        // Matched through tag1 only, so tag1 must be handled on its own.
+        $item = $this->cache->getItem('key3')->set('value');
         $item->setTags(['tag1']);
         $this->cache->save($item);
+        // Matched by none of the invalidated tags.
+        $item = $this->cache->getItem('key4')->set('value');
+        $item->setTags(['tag3']);
+        $this->cache->save($item);
 
         $this->cache->invalidateTags(['tag1', 'tag2']);
         $this->assertFalse($this->cache->hasItem('key'), 'Item should be cleared when tag is invalidated');
         $this->assertFalse($this->cache->hasItem('key2'), 'Item should be cleared when tag is invalidated');
+        $this->assertFalse($this->cache->hasItem('key3'), 'Item should be cleared when tag is invalidated');
+        $this->assertTrue($this->cache->hasItem('key4'), 'An item tagged with none of the invalidated tags must survive');
 
         // Create a new item (no tags)
         $item = $this->cache->getItem('key')->set('value');
@@ -305,6 +327,34 @@ public function testInvalidateTags()
         $this->assertTrue($this->cache->hasItem('key'), 'Item k list should be removed when clearing the tags');
     }
 
+    public function testInvalidateTagsDoesNotAffectOtherNamespaces()
+    {
+        if (isset($this->skippedTests[__FUNCTION__])) {
+            $this->markTestSkipped($this->skippedTests[__FUNCTION__]);
+        }
+
+        $other = $this->createCachePoolWithOtherNamespace();
+
+        if (null === $other) {
+            $this->markTestSkipped('This implementation cannot provide a second pool on the same storage with another namespace.');
+        }
+
+        try {
+            $this->cache->save($this->cache->getItem('key')->set('value')->setTags(['tag1']));
+            $other->save($other->getItem('key')->set('other value')->setTags(['tag1']));
+
+            $this->assertTrue($this->cache->invalidateTags(['tag1']));
+            $this->assertFalse($this->cache->hasItem('key'), 'The invalidated item should be gone from its own pool.');
+
+            $otherItem = $other->getItem('key');
+            $this->assertTrue($otherItem->isHit(), 'Invalidating a tag must not reach items of a pool using another namespace on the same storage.');
+            $this->assertSame('other value', $otherItem->get(), 'The item stored in the other namespace must keep its own value.');
+        } finally {
+            // The tearDownService() hook only clears $this->cache, so the other pool is cleared here.
+            $other->clear();
+        }
+    }
+
     public function testInvalidateTagsValidatesEveryTagBeforeMutation()
     {
         if (isset($this->skippedTests[__FUNCTION__])) {
diff --git a/tests/CachePoolTest.php b/tests/CachePoolTest.php
index 9586745..dda4adf 100644
--- a/tests/CachePoolTest.php
+++ b/tests/CachePoolTest.php
@@ -25,6 +25,8 @@ final class CachePoolTest extends CachePoolContract
 {
     private ?string $namespace = null;
 
+    private ?string $otherNamespace = null;
+
     public function createCachePool(): CacheItemPoolInterface
     {
         $this->namespace ??= bin2hex(random_bytes(16));
@@ -32,6 +34,13 @@ public function createCachePool(): CacheItemPoolInterface
         return new ValidatingCachePool(new FilesystemAdapter($this->namespace));
     }
 
+    public function createCachePoolWithOtherNamespace(): CacheItemPoolInterface
+    {
+        $this->otherNamespace ??= bin2hex(random_bytes(16));
+
+        return new ValidatingCachePool(new FilesystemAdapter($this->otherNamespace));
+    }
+
     public function testDataProvidersExposeCases()
     {
         self::assertNotEmpty(self::invalidKeys());
diff --git a/tests/Fixtures/TaggableCachePool.php b/tests/Fixtures/TaggableCachePool.php
index bffb7d7..093ee82 100644
--- a/tests/Fixtures/TaggableCachePool.php
+++ b/tests/Fixtures/TaggableCachePool.php
@@ -16,19 +16,25 @@
 use Cache\TagInterop\TaggableCacheItemInterface;
 use Cache\TagInterop\TaggableCacheItemPoolInterface;
 use Psr\Cache\CacheItemInterface;
+use Symfony\Component\Cache\Adapter\AdapterInterface;
 use Symfony\Component\Cache\Adapter\ArrayAdapter;
+use Symfony\Component\Cache\Adapter\ProxyAdapter;
 use Symfony\Component\Cache\Exception\InvalidArgumentException;
 
 final class TaggableCachePool implements TaggableCacheItemPoolInterface
 {
-    private readonly ArrayAdapter $pool;
+    private readonly AdapterInterface $pool;
 
     /** @var array<string, array<string, string>> */
     private array $tagsByKey = [];
 
-    public function __construct()
+    /**
+     * Passing a storage and a namespace puts several pools on one key space, where the
+     * namespace is a real key prefix, as a shared table or collection would.
+     */
+    public function __construct(?AdapterInterface $storage = null, string $namespace = '')
     {
-        $this->pool = new ArrayAdapter();
+        $this->pool = null === $storage ? new ArrayAdapter() : new ProxyAdapter($storage, $namespace);
     }
 
     public function getItem(string $key): TaggableCacheItemInterface
diff --git a/tests/TaggableCachePoolTest.php b/tests/TaggableCachePoolTest.php
index 34fa489..539f90c 100644
--- a/tests/TaggableCachePoolTest.php
+++ b/tests/TaggableCachePoolTest.php
@@ -17,12 +17,25 @@
 use Cache\IntegrationTests\Tests\Fixtures\TaggableCachePool;
 use Cache\TagInterop\TaggableCacheItemPoolInterface;
 use PHPUnit\Framework\SkippedTest;
+use Symfony\Component\Cache\Adapter\ArrayAdapter;
 
 final class TaggableCachePoolTest extends TaggableCachePoolContract
 {
+    private ?ArrayAdapter $storage = null;
+
     public function createCachePool(): TaggableCacheItemPoolInterface
     {
-        return new TaggableCachePool();
+        return new TaggableCachePool($this->sharedStorage(), 'first');
+    }
+
+    public function createCachePoolWithOtherNamespace(): TaggableCacheItemPoolInterface
+    {
+        return new TaggableCachePool($this->sharedStorage(), 'second');
+    }
+
+    private function sharedStorage(): ArrayAdapter
+    {
+        return $this->storage ??= new ArrayAdapter();
     }
 
     public function testDataProviderExposesCases()