diff --git a/tests/TapFunctionTest.php b/tests/TapFunctionTest.php
new file mode 100644
index 0000000..49b8f54
--- /dev/null
+++ b/tests/TapFunctionTest.php
@@ -0,0 +1,95 @@
+<?php
+
+namespace Tests\Koded\Stdlib;
+
+use Error;
+use Koded\Stdlib\Arguments;
+use Koded\Stdlib\Config;
+use Koded\Stdlib\Tapped;
+use PHPUnit\Framework\TestCase;
+use function Koded\Stdlib\tap;
+
+class TapFunctionTest extends TestCase
+{
+    use ObjectPropertyTrait;
+
+    public function test_object_with_callback()
+    {
+        $conf = tap(new Config, function(Config $c) {
+            $c->silent(true);
+            $c->foo = 'bar';
+        });
+
+        $this->assertInstanceOf(Config::class, $conf);
+        $this->assertTrue($this->property($conf, 'silent'));
+        $this->assertSame('bar', $conf->foo);
+    }
+
+    public function test_object_without_callback()
+    {
+        $conf = tap(new Config);
+        $conf->foo = 'bar';
+
+        $this->assertInstanceOf(Tapped::class, $conf);
+        $this->assertSame('bar', $conf->foo);
+    }
+
+    public function test_with_array_value()
+    {
+        $arr = tap([], function(&$data) {
+            $data['foo'] = 'bar';
+        });
+
+        $this->assertSame(['foo' => 'bar'], $arr);
+    }
+
+    public function test_chainable_methods()
+    {
+        $data = tap(new Arguments(['foo' => 'bar']), function ($args) {
+            $args
+                ->set('bar', [1, 2 , 3])
+                ->delete('bar.1')
+                ->import([
+                    100 => true,
+                    101 => false,
+                    102 => true
+                ]);
+        });
+
+        $this->assertSame(
+            [
+                'foo' => 'bar',
+                'bar' => [1, 2 ,3],
+                100 => true,
+                101 => false,
+                102 => true
+            ],
+            $data->toArray()
+        );
+    }
+
+    public function test_with_primitive_value()
+    {
+        $val1 = tap(42, function($v) {
+            $v = 'fubar';
+        });
+        $this->assertSame(42, $val1,
+            'The tapped value is not changed');
+
+        $val2 = tap(42, function(&$v) {
+            $v = 'fubar';
+        });
+        $this->assertSame('fubar', $val2,
+            'The tapped value is changed (passed by reference)');
+    }
+
+    public function test_unreasonable_use()
+    {
+        $this->expectException(Error::class);
+        $this->expectExceptionMessage('Attempt to assign property "foo" on int');
+
+        tap(42, function($v) {
+            $v->foo = 'bar';
+        });
+    }
+}