diff --git a/README.md b/README.md
index 27d31a5..36461f2 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,6 @@
 # VDF Converter
 
 ![Tests](https://github.com/exayer/vdf-converter/workflows/Tests/badge.svg)
-[![Total Downloads](https://img.shields.io/packagist/dt/EXayer/vdf-converter)](https://packagist.org/packages/exayer/vdf-converter)
 ![Latest Stable Version](https://img.shields.io/packagist/v/exayer/vdf-converter)
 
 A memory efficient parser for the Valve Data Format (*.vdf) written in PHP.
@@ -144,7 +143,7 @@ After creating your formatter, you can specify its class name in the `uniqueKeyF
 You can also specify a signer for a specific webhook call:
 
 ```php
-$config = (new VdfConverterConfig())
+$config = VdfConverterConfig::create()
     ->uniqueKeyFormatter(YourCustomFormatter::class);
 
 $iterator = VdfConverter::fromString($vdf, $config);
diff --git a/tests/ParserTest.php b/tests/ParserTest.php
index b4db7be..6d8cc52 100644
--- a/tests/ParserTest.php
+++ b/tests/ParserTest.php
@@ -5,6 +5,7 @@
 use EXayer\VdfConverter\Exception\CouldNotParseException;
 use EXayer\VdfConverter\Lexer;
 use EXayer\VdfConverter\Parser;
+use EXayer\VdfConverter\VdfConverterConfig;
 use PHPUnit\Framework\TestCase;
 
 class ParserTest extends TestCase
@@ -16,7 +17,7 @@ class ParserTest extends TestCase
      */
     public function testSyntax($vdf, $expectedResult)
     {
-        $parser = new Parser(new Lexer(new \ArrayIterator([$vdf])));
+        $parser = new Parser(new Lexer(new \ArrayIterator([$vdf])), new VdfConverterConfig());
         $result = iterator_to_array($parser);
 
         $this->assertEquals($expectedResult, $result);
@@ -87,13 +88,13 @@ public function syntaxDataProvider()
                 [
                     'a' => [
                         'b' => 1,
-                        'x' => ['x' => 1, 'x__2' => 2],
+                        'x' => ['x' => 1, 'x__[2]' => 2],
                         'e' => [
-                            'f' => ['x' => 1, '' => 1, '__2' => 2, 'x__2' => 2],
-                            'f__2' => [],
+                            'f' => ['x' => 1, '' => 1, '__[2]' => 2, 'x__[2]' => 2],
+                            'f__[2]' => [],
                         ],
-                        'x__2' => [],
-                        'e__2' => [],
+                        'x__[2]' => [],
+                        'e__[2]' => [],
                     ],
                 ],
             ],
@@ -103,14 +104,14 @@ public function syntaxDataProvider()
 
                 [
                     'a' => 1,
-                    'b' => ['c' => 1, 'c__2' => 2],
-                    'a__2' => [
-                        'b' => ['c' => 1, 'c__2' => 2],
-                        'b__2' => [],
+                    'b' => ['c' => 1, 'c__[2]' => 2],
+                    'a__[2]' => [
+                        'b' => ['c' => 1, 'c__[2]' => 2],
+                        'b__[2]' => [],
                     ],
-                    'a__3' => [],
+                    'a__[3]' => [],
                     'c' => [],
-                    'c__2' => [],
+                    'c__[2]' => [],
                 ],
             ],
             // all duplicates
@@ -118,13 +119,13 @@ public function syntaxDataProvider()
                 '{"x" "1" "x" {"x" "1" "x" "2"} "x" {"x" {"x" "1" "x" "2"} "x" {}} "x" {} "x" {}}',
                 [
                     'x' => 1,
-                    'x__2' => ['x' => 1, 'x__2' => 2],
-                    'x__3' => [
-                        'x' => ['x' => 1, 'x__2' => 2],
-                        'x__2' => [],
+                    'x__[2]' => ['x' => 1, 'x__[2]' => 2],
+                    'x__[3]' => [
+                        'x' => ['x' => 1, 'x__[2]' => 2],
+                        'x__[2]' => [],
                     ],
-                    'x__4' => [],
-                    'x__5' => [],
+                    'x__[4]' => [],
+                    'x__[5]' => [],
                 ],
             ],
         ];
@@ -138,7 +139,7 @@ public function testSyntaxError(string $brokenVdf)
     {
         $this->expectException(CouldNotParseException::class);
 
-        iterator_to_array(new Parser(new Lexer(new \ArrayIterator([$brokenVdf]))));
+        iterator_to_array(new Parser(new Lexer(new \ArrayIterator([$brokenVdf])), new VdfConverterConfig()));
     }
 
     public function syntaxErrorDataProvider()
@@ -162,7 +163,7 @@ public function testUnexpectedEndError(string $vdf)
     {
         $this->expectExceptionMessage(CouldNotParseException::unexpectedEnding()->getMessage());
 
-        iterator_to_array(new Parser(new Lexer(new \ArrayIterator([$vdf]))));
+        iterator_to_array(new Parser(new Lexer(new \ArrayIterator([$vdf])), new VdfConverterConfig()));
     }
 
     public function unexpectedEndExceptionDataProvider()
diff --git a/tests/UniqueKey/DefaultFormatterTest.php b/tests/UniqueKey/DefaultFormatterTest.php
new file mode 100644
index 0000000..98285a7
--- /dev/null
+++ b/tests/UniqueKey/DefaultFormatterTest.php
@@ -0,0 +1,17 @@
+<?php
+
+namespace EXayer\VdfConverter\Tests\UniqueKey;
+
+use EXayer\VdfConverter\UniqueKey\DefaultFormatter;
+use PHPUnit\Framework\TestCase;
+
+class DefaultFormatterTest extends TestCase
+{
+    public function testBuildName()
+    {
+        $formatter = new DefaultFormatter();
+        $formattedKey = $formatter->buildKeyName('sample_key', 9);
+
+        $this->assertEquals($formattedKey, 'sample_key__[9]');
+    }
+}
\ No newline at end of file
diff --git a/tests/UniqueKeyTest.php b/tests/UniqueKey/UniqueKeyTest.php
similarity index 81%
rename from tests/UniqueKeyTest.php
rename to tests/UniqueKey/UniqueKeyTest.php
index 890553b..188baa7 100644
--- a/tests/UniqueKeyTest.php
+++ b/tests/UniqueKey/UniqueKeyTest.php
@@ -1,8 +1,9 @@
 <?php
 
-namespace EXayer\VdfConverter\Tests;
+namespace EXayer\VdfConverter\Tests\UniqueKey;
 
-use EXayer\VdfConverter\UniqueKeyHandler;
+use EXayer\VdfConverter\UniqueKey\DefaultFormatter;
+use EXayer\VdfConverter\UniqueKey\UniqueKeyHandler;
 use PHPUnit\Framework\TestCase;
 
 class UniqueKeyTest extends TestCase
@@ -15,7 +16,7 @@ class UniqueKeyTest extends TestCase
      */
     public function testStorage(array $initStorage, array $levelsToClear, array $expected)
     {
-        $uniqueKey = new UniqueKeyHandler();
+        $uniqueKey = new UniqueKeyHandler(new DefaultFormatter());
 
         foreach ($initStorage as $pairs) {
             foreach ($pairs as $level => $key) {
@@ -44,7 +45,7 @@ public function storageDataProvider()
             [
                 [[1 => 'key'], [1 => 'key']],
                 [],
-                [1, 'key', 'key__3']
+                [1, 'key', 'key__[3]']
             ],
             [
                 [[1 => 'key'], [1 => 'key'], [2 => 'key'], [3 => 'key']],
@@ -54,7 +55,7 @@ public function storageDataProvider()
             [
                 [[1 => 'key'], [2 => 'key'], [3 => 'key']],
                 [2, 3],
-                [1, 'key', 'key__2']
+                [1, 'key', 'key__[2]']
             ],
         ];
     }
diff --git a/tests/VdfConverterConfigTest.php b/tests/VdfConverterConfigTest.php
new file mode 100644
index 0000000..78fb014
--- /dev/null
+++ b/tests/VdfConverterConfigTest.php
@@ -0,0 +1,16 @@
+<?php
+
+use EXayer\VdfConverter\UniqueKey\DefaultFormatter;
+use EXayer\VdfConverter\VdfConverterConfig;
+use PHPUnit\Framework\TestCase;
+
+class VdfConverterConfigTest extends TestCase
+{
+    public function testUniqueKeyFormatterCreation()
+    {
+        $config = VdfConverterConfig::create()
+            ->uniqueKeyFormatter(DefaultFormatter::class);
+
+        $this->assertEquals(new DefaultFormatter(), $config->getUniqueKeyFormatter());
+    }
+}
\ No newline at end of file