diff --git a/tests/mock/RepoEntity.php b/tests/mock/RepoEntity.php
new file mode 100644
index 0000000..01bbb45
--- /dev/null
+++ b/tests/mock/RepoEntity.php
@@ -0,0 +1,40 @@
+<?php
+
+namespace Mock;
+
+use Palladium\Contract\HasId;
+
+class RepoEntity implements HasId
+{
+    private $value;
+
+
+    public function __construct($value = 'default')
+    {
+        $this->value = $value;
+    }
+
+
+    public function getId()
+    {
+        return $this->value;
+    }
+
+
+    public function setId($value)
+    {
+        $this->value = $value;
+    }
+
+
+    public function setAction($action)
+    {
+        $this->value = $action;
+    }
+
+
+    public function getAction()
+    {
+        return $this->value;
+    }
+}
diff --git a/tests/mock/RepoMapper.php b/tests/mock/RepoMapper.php
new file mode 100644
index 0000000..b8fed8f
--- /dev/null
+++ b/tests/mock/RepoMapper.php
@@ -0,0 +1,38 @@
+<?php
+
+namespace Mock;
+
+use Palladium\Component\DataMapper;
+
+class RepoMapper extends DataMapper
+{
+    private $value;
+
+    public function __construct($value = null)
+    {
+        $this->value = $value;
+    }
+
+    public function fetch(RepoEntity $entity)
+    {
+        $entity->setAction('loaded');
+        return $this->value;
+    }
+
+    public function store(RepoEntity $entity)
+    {
+        $entity->setAction('saved');
+        return $this->value;
+    }
+
+    public function remove(RepoEntity $entity)
+    {
+        $entity->setAction('deleted');
+        return $this->value;
+    }
+
+    public function exists(RepoEntity $entity)
+    {
+        return $this->value;
+    }
+}
diff --git a/tests/unit/Palladium/Repository/IdentityTest.php b/tests/unit/Palladium/Repository/IdentityTest.php
new file mode 100644
index 0000000..a3e6dd8
--- /dev/null
+++ b/tests/unit/Palladium/Repository/IdentityTest.php
@@ -0,0 +1,122 @@
+<?php
+
+namespace Palladium\Repository;
+
+use PHPUnit\Framework\TestCase;
+use PDO;
+use PDOStatement;
+use Palladium\Entity;
+
+/**
+ * @covers Palladium\Repository\Identity
+ * @SuppressWarnings(PHPMD.CamelCaseMethodName)
+ * @SuppressWarnings(PHPMD.TooManyPublicMethods)
+ */
+final class IdentityTest extends TestCase
+{
+    /**
+     * @test
+     */
+    public function use_assigned_mapper_for_loading_entity()
+    {
+        $instance = new Identity(new \Mock\Factory([
+            \Mock\RepoMapper::class => new \Mock\RepoMapper,
+        ]));
+        $instance->define(\Mock\RepoEntity::class, \Mock\RepoMapper::class);
+
+        $item = new \Mock\RepoEntity;
+        $instance->load($item);
+
+        $this->assertSame('loaded', $item->getAction());
+    }
+
+
+    /**
+     * @test
+     */
+    public function use_assigned_mapper_for_storing_entity()
+    {
+        $instance = new Identity(new \Mock\Factory([
+            \Mock\RepoMapper::class => new \Mock\RepoMapper,
+        ]));
+        $instance->define(\Mock\RepoEntity::class, \Mock\RepoMapper::class);
+
+        $item = new \Mock\RepoEntity;
+        $instance->save($item);
+
+        $this->assertSame('saved', $item->getAction());
+    }
+
+
+    /**
+     * @test
+     */
+    public function use_assigned_mapper_for_deleting_entity()
+    {
+        $instance = new Identity(new \Mock\Factory([
+            \Mock\RepoMapper::class => new \Mock\RepoMapper,
+        ]));
+        $instance->define(\Mock\RepoEntity::class, \Mock\RepoMapper::class);
+
+        $item = new \Mock\RepoEntity;
+        $instance->delete($item);
+
+        $this->assertSame('deleted', $item->getAction());
+    }
+
+
+    /**
+     * @test
+     */
+    public function use_assigned_mapper_for_checking_whether_entity_exists()
+    {
+        $instance = new Identity(new \Mock\Factory([
+            \Mock\RepoMapper::class => new \Mock\RepoMapper(true),
+        ]));
+        $instance->define(\Mock\RepoEntity::class, \Mock\RepoMapper::class);
+
+        $item = new \Mock\RepoEntity;
+        $this->assertSame(true, $instance->has($item));
+    }
+
+
+    /**
+     * @test
+     */
+    public function deny_definition_of_fake_entity_in_repo()
+    {
+        $this->expectException(\RuntimeException::class);
+
+        $instance = new Identity(new \Mock\Factory([]));
+        $instance->define('FooBar', \Mock\RepoMapper::class);
+    }
+
+
+    /**
+     * @test
+     */
+    public function deny_definition_of_fake_mapper_in_repo()
+    {
+        $this->expectException(\RuntimeException::class);
+
+        $instance = new Identity(new \Mock\Factory([]));
+        $instance->define(\Mock\RepoEntity::class, 'FooBar');
+    }
+
+
+    /**
+     * @test
+     */
+    public function deny_override_with_undefined_mapper()
+    {
+        $this->expectException(\RuntimeException::class);
+
+        $instance = new Identity(new \Mock\Factory([
+            \Mock\RepoMapper::class => new \Mock\RepoMapper,
+        ]));
+        $instance->define(\Mock\RepoEntity::class, \Mock\RepoMapper::class);
+
+        $item = new \Mock\RepoEntity;
+        $instance->load($item, 'FooBar');
+    }
+}