diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 294b48c..88b99a7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -3,34 +3,12 @@ name: CI
 on: [push]
 
 jobs:
-  phpunit:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macOS-latest]
-        php-version: ['8.2']
-    name: 'PHPUnit'
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-      - name: Setup PHP
-        uses: shivammathur/setup-php@v2
-        with:
-          php-version: ${{ matrix.php-version }}
-          extensions: mbstring, intl
-          coverage: none
-      - name: Composer
-        uses: "ramsey/composer-install@v2"
-      - name: PHPUnit
-        run: vendor/bin/phpunit
-        env:
-          BLACKBOX_SET_SIZE: 20
   blackbox:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest]
-        php-version: ['8.2']
+        php-version: ['8.2', '8.3']
         dependency-versions: ['lowest', 'highest']
     name: 'BlackBox'
     steps:
@@ -48,14 +26,16 @@ jobs:
           dependency-versions: ${{ matrix.dependencies }}
       - name: BlackBox
         run: php blackbox.php
-  blackbox_coverage:
+        env:
+          BLACKBOX_SET_SIZE: 20
+  coverage:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
         os: [ubuntu-latest, macOS-latest]
-        php-version: ['8.2']
+        php-version: ['8.2', '8.3']
         dependency-versions: ['lowest', 'highest']
-    name: 'BlackBox Coverage'
+    name: 'Coverage'
     steps:
       - name: Checkout
         uses: actions/checkout@v2
@@ -73,30 +53,6 @@ jobs:
         run: php blackbox.php
         env:
           ENABLE_COVERAGE: 'true'
-      - uses: codecov/codecov-action@v1
-        with:
-          token: ${{ secrets.CODECOV_TOKEN }}
-  coverage:
-    runs-on: ${{ matrix.os }}
-    strategy:
-      matrix:
-        os: [ubuntu-latest, macOS-latest]
-        php-version: ['8.2']
-    name: 'Coverage'
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-      - name: Setup PHP
-        uses: shivammathur/setup-php@v2
-        with:
-          php-version: ${{ matrix.php-version }}
-          extensions: mbstring, intl
-          coverage: xdebug
-      - name: Composer
-        uses: "ramsey/composer-install@v2"
-      - name: PHPUnit
-        run: vendor/bin/phpunit --coverage-clover=coverage.clover
-        env:
           BLACKBOX_SET_SIZE: 1
       - uses: codecov/codecov-action@v1
         with:
@@ -105,7 +61,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php-version: ['8.2']
+        php-version: ['8.2', '8.3']
     name: 'Psalm'
     steps:
       - name: Checkout
diff --git a/.github/workflows/documentation.yml b/.github/workflows/documentation.yml
deleted file mode 100644
index 9f64211..0000000
--- a/.github/workflows/documentation.yml
+++ /dev/null
@@ -1,26 +0,0 @@
-name: Documentation
-
-on:
-  push:
-    branches: [master]
-
-jobs:
-  publish:
-    runs-on: ubuntu-latest
-    name: 'Publish documentation'
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v2
-      - name: Setup PHP
-        uses: shivammathur/setup-php@v2
-        with:
-          php-version: '8.0'
-      - name: Install halsey/journal
-        run: composer global require halsey/journal
-      - name: Generate
-        run: composer global exec 'journal generate'
-      - name: Push
-        uses: peaceiris/actions-gh-pages@v3
-        with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: ./.tmp_journal/
diff --git a/.gitignore b/.gitignore
index 3ccfb21..987e2a2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,2 @@
 composer.lock
 vendor
-.phpunit.result.cache
-.couscous
-.php-cs-fixer.cache
diff --git a/.journal b/.journal
deleted file mode 100644
index 5167faf..0000000
--- a/.journal
+++ /dev/null
@@ -1,83 +0,0 @@
-<?php
-declare(strict_types = 1);
-
-use Halsey\Journal\{
-    Config,
-    Menu\Entry,
-};
-use Innmind\Url\Path;
-
-return static function(Config $config): Config
-{
-    return $config
-        ->package('innmind', 'immutable', null, 'Immutable')
-        ->locatedAt(Path::of('docs/'))
-        ->menu(
-            Entry::markdown(
-                'Getting started',
-                Path::of('README.md'),
-            ),
-            Entry::section(
-                'Structures',
-                Entry::markdown(
-                    'Sequence',
-                    Path::of('SEQUENCE.md'),
-                ),
-                Entry::markdown(
-                    'Set',
-                    Path::of('SET.md'),
-                ),
-                Entry::markdown(
-                    'Map',
-                    Path::of('MAP.md'),
-                ),
-                Entry::markdown(
-                    'Str',
-                    Path::of('STR.md'),
-                ),
-                Entry::markdown(
-                    'RegExp',
-                    Path::of('REGEXP.md'),
-                ),
-                Entry::markdown(
-                    'Maybe',
-                    Path::of('MAYBE.md'),
-                ),
-                Entry::markdown(
-                    'Either',
-                    Path::of('EITHER.md'),
-                ),
-                Entry::markdown(
-                    'State',
-                    Path::of('STATE.md'),
-                ),
-                Entry::markdown(
-                    'Fold',
-                    Path::of('FOLD.md'),
-                ),
-                Entry::markdown(
-                    'Monoids',
-                    Path::of('MONOIDS.md'),
-                ),
-            )->alwaysOpen(),
-            Entry::section(
-                'Use cases',
-                Entry::markdown(
-                    'How to read a file',
-                    Path::of('LAZY_FILE.md'),
-                ),
-                Entry::markdown(
-                    'Parsing strings',
-                    Path::of('PARSING.md'),
-                ),
-            )->alwaysOpen(),
-            Entry::markdown(
-                'Blackbox',
-                Path::of('BLACKBOX.md'),
-            ),
-            Entry::markdown(
-                'Philosophy',
-                Path::of('PHILOSOPHY.md'),
-            ),
-        );
-};
diff --git a/CHANGELOG.md b/CHANGELOG.md
index b041e44..357110d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,15 @@
 # Changelog
 
+## 5.0.0 - 2023-09-16
+
+### Changed
+
+- `Innmind\Immutable\Str` only use `Innmind\Immutable\Str\Encoding` to represent the encoding to work with
+
+### Removed
+
+- `Fixtures\Innmind\Immutable\Map`
+
 ## 4.15.0 - 2023-07-08
 
 ### Added
diff --git a/README.md b/README.md
index f3ac552..a18c096 100644
--- a/README.md
+++ b/README.md
@@ -6,9 +6,19 @@
 
 A set of classes to wrap PHP primitives to build immutable data.
 
+[Documentation](docs/)
+
+## Installation
+
+```sh
+composer require innmind/immutable
+```
+
+## Usage
+
 Here are some examples of what you can do:
 
-## Sequence
+### Sequence
 
 To be used to wrap an ordered list of elements (elements can be of mixed types).
 
@@ -38,7 +48,7 @@ $lines->foreach(fn($line) => echo($line));
 
 For a complete list of methods check [`Sequence`](src/Sequence.php).
 
-## Set
+### Set
 
 To be used as a collection of unordered elements (elements must be of the same type).
 
@@ -52,7 +62,7 @@ $set->add(42.0); // psalm will raise an error
 
 For a complete list of methods check [`Set`](src/Set.php).
 
-## Map
+### Map
 
 To be used as a collection of key/value pairs (both keys and values must be of the same type).
 
@@ -72,7 +82,7 @@ $map->values()->toList(); // [42, 66]
 
 For a complete list of methods check [`Map`](src/Map.php).
 
-## Strings
+### Strings
 
 ```php
 use Innmind\Immutable\Str;
@@ -100,9 +110,9 @@ $regexp->matches(Str::of('foobar')); // false
 $regexp->capture(Str::of('foo123bar')); // Map<int|string, Str> with index `i` set to Str::of('123')
 ```
 
-## [BlackBox](https://github.com/innmind/blackbox/)
+### [BlackBox](https://github.com/innmind/blackbox/)
 
-This library provides 3 `Set`s that can be used with [`innmind/black-box`](https://packagist.org/packages/innmind/black-box).
+This library provides 2 `Set`s that can be used with [`innmind/black-box`](https://packagist.org/packages/innmind/black-box).
 
 You can use them as follow:
 
@@ -121,10 +131,6 @@ class SomeTest extends \PHPUnit\Framework\TestCase
     {
         $this
             ->forAll(
-                Immutable\Map::of(
-                    Set\Integers::any(),
-                    Set\Strings::any(),
-                ),
                 Immutable\Set::of(
                     Set\RealNumbers::any(),
                 ),
@@ -132,8 +138,7 @@ class SomeTest extends \PHPUnit\Framework\TestCase
                     Set\Uuid::any(),
                 ),
             )
-            ->then(function($map, $set, $sequence) {
-                // $map is an instance of \Innmind\Immutable\Map<int, string>
+            ->then(function($set, $sequence) {
                 // $set is an instance of \Innmind\Immutable\Set<float>
                 // $sequence is an instance of \Innmind\Immutable\Sequence<string>
 
diff --git a/blackbox.php b/blackbox.php
index a8cd695..bf1804d 100644
--- a/blackbox.php
+++ b/blackbox.php
@@ -10,18 +10,19 @@
 };
 
 Application::new($argv)
-    ->codeCoverage(
-        CodeCoverage::of(
-            __DIR__.'/src/',
-            __DIR__.'/proofs/',
-            __DIR__.'/fixtures/',
-        )
-            ->dumpTo('coverage.clover')
-            ->enableWhen(\getenv('ENABLE_COVERAGE') !== false),
+    ->when(
+        \getenv('ENABLE_COVERAGE') !== false,
+        static fn(Application $app) => $app
+            ->codeCoverage(
+                CodeCoverage::of(
+                    __DIR__.'/src/',
+                    __DIR__.'/proofs/',
+                    __DIR__.'/fixtures/',
+                )
+                    ->dumpTo('coverage.clover')
+                    ->enableWhen(true),
+            )
+            ->scenariiPerProof(1),
     )
-    ->scenariiPerProof(match (\getenv('ENABLE_COVERAGE')) {
-        false => 100,
-        default => 1,
-    })
     ->tryToProve(Load::everythingIn(__DIR__.'/proofs/'))
     ->exit();
diff --git a/composer.json b/composer.json
index fd11042..90bc86c 100644
--- a/composer.json
+++ b/composer.json
@@ -30,9 +30,8 @@
         }
     },
     "require-dev": {
-        "phpunit/phpunit": "~10.0",
         "vimeo/psalm": "~5.6",
-        "innmind/black-box": "~5.0",
+        "innmind/black-box": "^5.5.1",
         "innmind/coding-standard": "~2.0"
     },
     "conflict": {
diff --git a/docs/EITHER.md b/docs/EITHER.md
index bd9a13c..92453df 100644
--- a/docs/EITHER.md
+++ b/docs/EITHER.md
@@ -32,7 +32,8 @@ function accessResource(User $user): Either {
 }
 ```
 
-> **Note** `ServerRequest`, `User`, `Resource` and `Error` are imaginary classes.
+> **Note**
+> `ServerRequest`, `User`, `Resource` and `Error` are imaginary classes.
 
 ## `::left()`
 
@@ -42,7 +43,8 @@ This builds an `Either` instance with the given value in the left hand side.
 $either = Either::left($anyValue);
 ```
 
-> **Note** usually this side is used for errors.
+> **Note**
+> usually this side is used for errors.
 
 ## `::right()`
 
@@ -52,7 +54,8 @@ This builds an `Either` instance with the given value in the right hand side.
 $either = Either::right($anyValue);
 ```
 
-> **Note** usually this side is used for valid values.
+> **Note**
+> usually this side is used for valid values.
 
 ## `::defer()`
 
@@ -110,7 +113,8 @@ $response = identify($serverRequest)
     );
 ```
 
-> **Note** `Response` is an imaginary class.
+> **Note**
+> `Response` is an imaginary class.
 
 ## `->otherwise()`
 
diff --git a/docs/MAP.md b/docs/MAP.md
index 1f9fcef..86c2dc7 100644
--- a/docs/MAP.md
+++ b/docs/MAP.md
@@ -177,7 +177,8 @@ $values = Map::of([24, 1], [42, 2])->values();
 $values->equals(Sequence::of(1, 2)); // true
 ```
 
-> **Note** it returns a `Sequence` because it can contain duplicates, the order is not guaranteed as a map is not ordered.
+> **Note**
+> it returns a `Sequence` because it can contain duplicates, the order is not guaranteed as a map is not ordered.
 
 ## `->map()`
 
diff --git a/docs/MAYBE.md b/docs/MAYBE.md
index a724dea..f96bcd5 100644
--- a/docs/MAYBE.md
+++ b/docs/MAYBE.md
@@ -190,7 +190,8 @@ $vars = Sequence::of('DB_URL', 'MAILER_URL', /* and so on */)
     ->flatMap(static fn($var) => env($var)->toSequence());
 ```
 
-> **Note** this example uses the `env` function defined at the start of this documentation.
+> **Note**
+> this example uses the `env` function defined at the start of this documentation.
 
 This is equivalent to:
 
diff --git a/docs/README.md b/docs/README.md
index 9107033..2c72926 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -2,13 +2,15 @@
 
 This project brings a set of immutable data structure to bring a uniformity on how to handle data.
 
+Before diving in the documentation you may want to read about the [philosophy](PHILOSOPHY.md) behind the structures design.
+
 ## Installation
 
 ```sh
 composer require innmind/immutable
 ```
 
-## Usage
+## Structures
 
 This library provides the 7 following structures:
 
@@ -25,3 +27,12 @@ This library provides the 7 following structures:
 See the documentation for each structure to understand how to use them.
 
 All structures are typed with [`vimeo/psalm`](https://psalm.dev), you must use it in order to verify that you use this library correctly.
+
+## Use cases
+
+- [How to read a file](LAZY_FILE.md)
+- [Parsing strings](PARSING.md)
+
+## Testing
+
+This package provides sets that can be used with [BlackBox](BLACKBOX.md).
diff --git a/docs/SEQUENCE.md b/docs/SEQUENCE.md
index 6e9b657..07863e8 100644
--- a/docs/SEQUENCE.md
+++ b/docs/SEQUENCE.md
@@ -49,7 +49,8 @@ Same as `::lazy()` except you don't need to manually build the generator.
 $sequence = Sequence::lazyStartingWith(1, 2, 3);
 ```
 
-> **Note** this is useful when you know the first items of the sequence and you'll `append` another lazy sequence at the end.
+> **Note**
+> this is useful when you know the first items of the sequence and you'll `append` another lazy sequence at the end.
 
 ## `::mixed()`
 
@@ -551,7 +552,8 @@ $lines = Sequence::of(...$chunks)
 $lines; // ['foo', 'bar', 'baz', '']
 ```
 
-> **Note** The `flatMap` is here in case there is only one chunk in the sequence, in which case the `aggregate` is not called
+> **Note**
+> The `flatMap` is here in case there is only one chunk in the sequence, in which case the `aggregate` is not called
 
 ## `->memoize()`
 
diff --git a/docs/STR.md b/docs/STR.md
index 9315c00..079ef77 100644
--- a/docs/STR.md
+++ b/docs/STR.md
@@ -16,11 +16,14 @@ $str instanceof Str; // true
 You can also specify the encoding to use for manupilating the string.
 
 ```php
-$str = Str::of('👋', 'UTF-8');
+$str = Str::of('👋', Str\Encoding::utf8);
 $str->length(); // 1
 Str::of('👋')->length(); // 4
 ```
 
+> **Note**
+> `Str\Encoding::utf8` is the default value when not specified
+
 ## `->toString()`
 
 This will return the encapsulated string.
@@ -34,7 +37,7 @@ Str::of('whataver')->toString(); // 'whatever'
 This will return the encoding used to manipulate the string.
 
 ```php
-Str::of('', 'UTF-8')->encoding()->equals(Str::of('UTF-8')); // true
+Str::of('', 'UTF-8')->encoding() === Str\Encoding::utf8; // true
 ```
 
 ## `->toEncoding()`
@@ -42,7 +45,7 @@ Str::of('', 'UTF-8')->encoding()->equals(Str::of('UTF-8')); // true
 Use this method to change the encoding used to manipulate the string.
 
 ```php
-Str::of('👋')->toEncoding('UTF-8');
+Str::of('👋')->toEncoding(Str\Encoding::utf8);
 ```
 
 ## `->split()`
@@ -112,7 +115,7 @@ Str::of('FOOBAR')->toUpper()->equals(Str::of('foobar'));
 Returns the length of the string depending on the used encoding.
 
 ```php
-Str::of('👋', 'UTF-8')->length(); // 1
+Str::of('👋', Str\Encoding::utf8)->length(); // 1
 Str::of('👋')->length(); // 4
 ```
 
@@ -122,7 +125,7 @@ Check if the string is an empty string.
 
 ```php
 Str::of('')->empty(); // true
-Str::of('', 'UTF-8')->empty(); // true
+Str::of('', Str\Encoding::utf8)->empty(); // true
 Str::of('null')->empty(); // false
 Str::of('0')->empty(); // false
 Str::of('false')->empty(); // false
@@ -336,7 +339,7 @@ Check if the 2 strings are equal.
 
 ```php
 Str::of('foo')->equals(Str::of('foo')); // true
-Str::of('foo')->equals(Str::of('foo', 'UTF-8')); // true
+Str::of('foo')->equals(Str::of('foo', Str\Encoding::utf8)); // true
 Str::of('foo')->equals(Str::of('bar')); // false
 ```
 
diff --git a/fixtures/Map.php b/fixtures/Map.php
deleted file mode 100644
index aa47176..0000000
--- a/fixtures/Map.php
+++ /dev/null
@@ -1,67 +0,0 @@
-<?php
-declare(strict_types = 1);
-
-namespace Fixtures\Innmind\Immutable;
-
-use Innmind\BlackBox\{
-    Set,
-    Random,
-};
-use Innmind\Immutable\{
-    Map as Structure,
-    Set as ISet,
-    Sequence as ISequence,
-};
-
-final class Map
-{
-    /**
-     * @deprecated Will be removed in the next major release
-     *
-     * @template I
-     * @template J
-     *
-     * @param Set<I> $keys
-     * @param Set<J> $values
-     *
-     * @return Set<Structure<I, J>>
-     */
-    public static function of(
-        Set $keys,
-        Set $values,
-        Set\Integers $sizes = null,
-    ): Set {
-        // this is not optimal but it allows to avoid a BC break
-        $sizes ??= Set\Integers::between(0, 100);
-        $range = [
-            $sizes->values(Random::default)->current()->unwrap(),
-            $sizes->values(Random::default)->current()->unwrap(),
-        ];
-        $min = \min($range);
-        $max = \max($range);
-
-        return Set\Decorate::immutable(
-            static fn(array $pairs): Structure => \array_reduce(
-                $pairs,
-                static fn(Structure $map, array $pair): Structure => ($map)($pair[0], $pair[1]),
-                Structure::of(),
-            ),
-            Set\Sequence::of(
-                Set\Randomize::of( // forced to randomize as the composite will try to reuse the same key
-                    Set\Composite::immutable(
-                        static fn($key, $value): array => [$key, $value],
-                        $keys,
-                        $values,
-                    ),
-                ),
-            )
-                ->between($min, $max)
-                ->filter(static function(array $pairs): bool {
-                    $keys = \array_column($pairs, 0);
-
-                    // checks unicity of values
-                    return ISequence::mixed(...$keys)->size() === ISet::mixed(...$keys)->size();
-                }),
-        );
-    }
-}
diff --git a/phpunit.xml.dist b/phpunit.xml.dist
deleted file mode 100644
index 2c4d515..0000000
--- a/phpunit.xml.dist
+++ /dev/null
@@ -1,23 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" colors="true" bootstrap="vendor/autoload.php" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.2/phpunit.xsd">
-  <extensions>
-    <bootstrap class="Innmind\BlackBox\PHPUnit\Extension">
-    </bootstrap>
-  </extensions>
-  <coverage/>
-  <testsuites>
-    <testsuite name="Immutable primitive wrappers test suite">
-      <directory>./tests</directory>
-    </testsuite>
-  </testsuites>
-  <source>
-    <include>
-      <directory>.</directory>
-    </include>
-    <exclude>
-      <directory>./tests</directory>
-      <directory>./vendor</directory>
-      <directory>./benchmarks</directory>
-    </exclude>
-  </source>
-</phpunit>
diff --git a/proofs/monoid/mergeMap.php b/proofs/monoid/mergeMap.php
index ce8fe7e..0c0b52a 100644
--- a/proofs/monoid/mergeMap.php
+++ b/proofs/monoid/mergeMap.php
@@ -1,18 +1,33 @@
 <?php
 declare(strict_types = 1);
 
-use Innmind\Immutable\Monoid\MergeMap;
+use Innmind\Immutable\{
+    Monoid\MergeMap,
+    Map,
+    Sequence,
+};
 use Innmind\BlackBox\Set;
-use Fixtures\Innmind\Immutable\Map;
 use Properties\Innmind\Immutable\Monoid;
 
 return static function() {
     $equals = static fn($a, $b) => $a->equals($b);
-    $set = Map::of(
-        Set\Integers::between(0, 200),
-        Set\Integers::between(0, 200),
-        Set\Integers::between(1, 10),
-    );
+    $set = Set\Sequence::of(
+        Set\Randomize::of( // forced to randomize as the composite will try to reuse the same key
+            Set\Composite::immutable(
+                static fn($key, $value): array => [$key, $value],
+                Set\Integers::between(0, 200),
+                Set\Integers::between(0, 200),
+            ),
+        ),
+    )
+        ->between(1, 10)
+        ->filter(static function(array $pairs): bool {
+            $keys = \array_column($pairs, 0);
+
+            // checks unicity of values
+            return Sequence::of(...$keys)->size() === Sequence::of(...$keys)->distinct()->size();
+        })
+        ->map(static fn($pairs) => Map::of(...$pairs));
 
     yield properties(
         'MergeMap properties',
diff --git a/proofs/phpunit.php b/proofs/phpunit.php
new file mode 100644
index 0000000..a1ef0da
--- /dev/null
+++ b/proofs/phpunit.php
@@ -0,0 +1,8 @@
+<?php
+declare(strict_types = 1);
+
+use Innmind\BlackBox\PHPUnit\Load;
+
+return static function() {
+    yield from Load::testsAt(__DIR__.'/../tests/');
+};
diff --git a/src/RegExp.php b/src/RegExp.php
index 74942a6..563d352 100644
--- a/src/RegExp.php
+++ b/src/RegExp.php
@@ -17,6 +17,7 @@ final class RegExp
 
     private function __construct(string $pattern)
     {
+        /** @psalm-suppress ArgumentTypeCoercion */
         if (@\preg_match($pattern, '') === false) {
             /** @psalm-suppress ImpureFunctionCall */
             throw new LogicException($pattern, \preg_last_error());
@@ -38,6 +39,7 @@ public static function of(string $pattern): self
      */
     public function matches(Str $string): bool
     {
+        /** @psalm-suppress ArgumentTypeCoercion */
         $value = \preg_match($this->pattern, $string->toString());
 
         if ($value === false) {
@@ -56,6 +58,7 @@ public function matches(Str $string): bool
     public function capture(Str $string): Map
     {
         $matches = [];
+        /** @psalm-suppress ArgumentTypeCoercion */
         $value = \preg_match($this->pattern, $string->toString(), $matches);
 
         if ($value === false) {
@@ -72,7 +75,7 @@ public function capture(Str $string): Map
                 $key,
                 Str::of(
                     (string) $match,
-                    $string->encoding()->toString(),
+                    $string->encoding(),
                 ),
             );
         }
diff --git a/src/Sequence/Defer.php b/src/Sequence/Defer.php
index fc04f3d..392f3e1 100644
--- a/src/Sequence/Defer.php
+++ b/src/Sequence/Defer.php
@@ -413,6 +413,7 @@ public function slice(int $from, int $until): Implementation
         return new self(
             (static function(\Iterator $values, int $from, int $until): \Generator {
                 $index = 0;
+
                 /** @var T $value */
                 foreach ($values as $value) {
                     if ($index >= $from && $index < $until) {
@@ -434,6 +435,7 @@ public function take(int $size): Implementation
         return new self(
             (static function(\Iterator $values, int $size): \Generator {
                 $taken = 0;
+
                 /** @var T $value */
                 foreach ($values as $value) {
                     if ($taken >= $size) {
diff --git a/src/Str.php b/src/Str.php
index 992efd0..3a169f1 100644
--- a/src/Str.php
+++ b/src/Str.php
@@ -11,16 +11,12 @@
 final class Str implements \Stringable
 {
     private string $value;
-    private string $encoding;
+    private Str\Encoding $encoding;
 
-    private function __construct(string $value, string $encoding = null)
+    private function __construct(string $value, Str\Encoding $encoding = null)
     {
         $this->value = $value;
-        /**
-         * @psalm-suppress ImpureFunctionCall
-         * @var string
-         */
-        $this->encoding = $encoding ?? \mb_internal_encoding();
+        $this->encoding = $encoding ?? Str\Encoding::utf8;
     }
 
     public function __toString(): string
@@ -30,15 +26,9 @@ public function __toString(): string
 
     /**
      * @psalm-pure
-     *
-     * @param string|Str\Encoding|null $encoding $encoding Strings will no longer be accepted in the next major release
      */
-    public static function of(string $value, string|Str\Encoding $encoding = null): self
+    public static function of(string $value, Str\Encoding $encoding = null): self
     {
-        if ($encoding instanceof Str\Encoding) {
-            $encoding = $encoding->toString();
-        }
-
         return new self($value, $encoding);
     }
 
@@ -60,15 +50,12 @@ public function toString(): string
         return $this->value;
     }
 
-    public function encoding(): self
+    public function encoding(): Str\Encoding
     {
-        return new self($this->encoding);
+        return $this->encoding;
     }
 
-    /**
-     * @param string|Str\Encoding $encoding $encoding Strings will no longer be accepted in the next major release
-     */
-    public function toEncoding(string|Str\Encoding $encoding): self
+    public function toEncoding(Str\Encoding $encoding): self
     {
         return self::of($this->value, $encoding);
     }
@@ -116,7 +103,7 @@ public function chunk(int $size = 1): Sequence
     {
         /** @var Sequence<self> */
         $sequence = Sequence::of();
-        $parts = \mb_str_split($this->value, $size, $this->encoding);
+        $parts = \mb_str_split($this->value, $size, $this->encoding->toString());
 
         foreach ($parts as $value) {
             $sequence = ($sequence)(new self($value, $this->encoding));
@@ -134,7 +121,7 @@ public function chunk(int $size = 1): Sequence
      */
     public function position(string|\Stringable $needle, int $offset = 0): Maybe
     {
-        $position = \mb_strpos($this->value, (string) $needle, $offset, $this->encoding);
+        $position = \mb_strpos($this->value, (string) $needle, $offset, $this->encoding->toString());
 
         if ($position === false) {
             /** @var Maybe<0|positive-int> */
@@ -184,7 +171,7 @@ public function toLower(): self
      */
     public function length(): int
     {
-        return \mb_strlen($this->value, $this->encoding);
+        return \mb_strlen($this->value, $this->encoding->toString());
     }
 
     public function empty(): bool
@@ -296,6 +283,7 @@ public function words(string|\Stringable $charlist = ''): Map
      */
     public function pregSplit(string|\Stringable $regex, int $limit = -1): Sequence
     {
+        /** @psalm-suppress ArgumentTypeCoercion */
         $strings = \preg_split((string) $regex, $this->value, $limit);
         /** @var Sequence<self> */
         $sequence = Sequence::of();
@@ -339,6 +327,7 @@ public function pregReplace(
         string|\Stringable $replacement,
         int $limit = -1,
     ): self {
+        /** @psalm-suppress ArgumentTypeCoercion */
         $value = \preg_replace(
             (string) $regex,
             (string) $replacement,
@@ -365,7 +354,7 @@ public function substring(int $start, int $length = null): self
             return $this;
         }
 
-        $sub = \mb_substr($this->value, $start, $length, $this->encoding);
+        $sub = \mb_substr($this->value, $start, $length, $this->encoding->toString());
 
         return new self($sub, $this->encoding);
     }
@@ -508,7 +497,7 @@ public function leftTrim(string $mask = null): self
      */
     public function contains(string|\Stringable $value): bool
     {
-        return \mb_strpos($this->value, (string) $value, 0, $this->encoding) !== false;
+        return \mb_strpos($this->value, (string) $value, 0, $this->encoding->toString()) !== false;
     }
 
     /**
@@ -520,7 +509,7 @@ public function startsWith(string|\Stringable $value): bool
             return true;
         }
 
-        return \mb_strpos($this->value, (string) $value, 0, $this->encoding) === 0;
+        return \mb_strpos($this->value, (string) $value, 0, $this->encoding->toString()) === 0;
     }
 
     /**
@@ -548,7 +537,7 @@ public function pregQuote(string|\Stringable $delimiter = ''): self
     }
 
     /**
-     * @param callable(string, string): string $map Second string is the encoding
+     * @param callable(string, Str\Encoding): string $map Second string is the encoding
      */
     public function map(callable $map): self
     {
@@ -557,7 +546,7 @@ public function map(callable $map): self
     }
 
     /**
-     * @param callable(string, string): self $map Second string is the encoding
+     * @param callable(string, Str\Encoding): self $map Second string is the encoding
      */
     public function flatMap(callable $map): self
     {
diff --git a/tests/AccumulateTest.php b/tests/AccumulateTest.php
index 4882d18..d1638e4 100644
--- a/tests/AccumulateTest.php
+++ b/tests/AccumulateTest.php
@@ -4,7 +4,7 @@
 namespace Tests\Innmind\Immutable;
 
 use Innmind\Immutable\Accumulate;
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class AccumulateTest extends TestCase
 {
diff --git a/tests/EitherTest.php b/tests/EitherTest.php
index 527c176..50e9eb3 100644
--- a/tests/EitherTest.php
+++ b/tests/EitherTest.php
@@ -4,9 +4,9 @@
 namespace Tests\Innmind\Immutable;
 
 use Innmind\Immutable\Either;
-use PHPUnit\Framework\TestCase;
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set,
 };
 
diff --git a/tests/Fixtures/MapTest.php b/tests/Fixtures/MapTest.php
deleted file mode 100644
index d92d65b..0000000
--- a/tests/Fixtures/MapTest.php
+++ /dev/null
@@ -1,42 +0,0 @@
-<?php
-declare(strict_types = 1);
-
-namespace Tests\Innmind\Immutable\Fixtures;
-
-use Innmind\Immutable\Map as Structure;
-use Innmind\BlackBox\{
-    PHPUnit\BlackBox,
-    Set,
-};
-use Fixtures\Innmind\Immutable\Map;
-use PHPUnit\Framework\TestCase;
-
-class MapTest extends TestCase
-{
-    use BlackBox;
-
-    public function testOf()
-    {
-        $this->assertInstanceOf(
-            Set::class,
-            Map::of(
-                Set\Strings::madeOf(Set\Chars::any())->between(1, 2),
-                Set\Strings::madeOf(Set\Chars::any())->between(1, 2),
-            ),
-        );
-    }
-
-    public function testGenerate()
-    {
-        $this
-            ->forAll(Map::of(
-                Set\Strings::madeOf(Set\Chars::any())->between(1, 2),
-                Set\Strings::madeOf(Set\Chars::any())->between(1, 2),
-                Set\Integers::between(0, 5),
-            ))
-            ->then(function($map) {
-                $this->assertInstanceOf(Structure::class, $map);
-                $this->assertLessThanOrEqual(5, $map->size());
-            });
-    }
-}
diff --git a/tests/Fixtures/SequenceTest.php b/tests/Fixtures/SequenceTest.php
index a78f004..eabbe9a 100644
--- a/tests/Fixtures/SequenceTest.php
+++ b/tests/Fixtures/SequenceTest.php
@@ -6,10 +6,10 @@
 use Innmind\Immutable\Sequence as Structure;
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set,
 };
 use Fixtures\Innmind\Immutable\Sequence;
-use PHPUnit\Framework\TestCase;
 
 class SequenceTest extends TestCase
 {
diff --git a/tests/Fixtures/SetTest.php b/tests/Fixtures/SetTest.php
index f478cf8..058b088 100644
--- a/tests/Fixtures/SetTest.php
+++ b/tests/Fixtures/SetTest.php
@@ -6,10 +6,10 @@
 use Innmind\Immutable\Set as Structure;
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set as DataSet,
 };
 use Fixtures\Innmind\Immutable\Set;
-use PHPUnit\Framework\TestCase;
 
 class SetTest extends TestCase
 {
diff --git a/tests/FoldTest.php b/tests/FoldTest.php
index 777e2a1..3660b80 100644
--- a/tests/FoldTest.php
+++ b/tests/FoldTest.php
@@ -4,9 +4,9 @@
 namespace Tests\Innmind\Immutable;
 
 use Innmind\Immutable\Fold;
-use PHPUnit\Framework\TestCase;
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set,
 };
 
diff --git a/tests/Map/DoubleIndexTest.php b/tests/Map/DoubleIndexTest.php
index 82826cb..132ee16 100644
--- a/tests/Map/DoubleIndexTest.php
+++ b/tests/Map/DoubleIndexTest.php
@@ -12,7 +12,7 @@
     Set,
     Sequence,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class DoubleIndexTest extends TestCase
 {
diff --git a/tests/Map/ObjectKeysTest.php b/tests/Map/ObjectKeysTest.php
index 48cee09..a4ce325 100644
--- a/tests/Map/ObjectKeysTest.php
+++ b/tests/Map/ObjectKeysTest.php
@@ -13,7 +13,7 @@
     Set,
     Sequence,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class ObjectKeysTest extends TestCase
 {
diff --git a/tests/Map/PrimitiveTest.php b/tests/Map/PrimitiveTest.php
index 760c007..dcd3a01 100644
--- a/tests/Map/PrimitiveTest.php
+++ b/tests/Map/PrimitiveTest.php
@@ -12,7 +12,7 @@
     Set,
     Sequence,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class PrimitiveTest extends TestCase
 {
diff --git a/tests/MapTest.php b/tests/MapTest.php
index 31e826e..434e295 100644
--- a/tests/MapTest.php
+++ b/tests/MapTest.php
@@ -10,7 +10,7 @@
     Set,
     Sequence,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class MapTest extends TestCase
 {
diff --git a/tests/MaybeTest.php b/tests/MaybeTest.php
index 2cf3c26..1f361e1 100644
--- a/tests/MaybeTest.php
+++ b/tests/MaybeTest.php
@@ -8,9 +8,9 @@
     Either,
     Predicate,
 };
-use PHPUnit\Framework\TestCase;
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set,
 };
 
diff --git a/tests/Monoid/AppendTest.php b/tests/Monoid/AppendTest.php
index d6ee095..072712b 100644
--- a/tests/Monoid/AppendTest.php
+++ b/tests/Monoid/AppendTest.php
@@ -8,7 +8,7 @@
     Monoid,
     Sequence,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class AppendTest extends TestCase
 {
diff --git a/tests/Monoid/ConcatTest.php b/tests/Monoid/ConcatTest.php
index 3f1a277..5ddbca1 100644
--- a/tests/Monoid/ConcatTest.php
+++ b/tests/Monoid/ConcatTest.php
@@ -8,7 +8,7 @@
     Monoid,
     Str,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class ConcatTest extends TestCase
 {
diff --git a/tests/Monoid/MergeMapTest.php b/tests/Monoid/MergeMapTest.php
index 2baf5b0..81d24ad 100644
--- a/tests/Monoid/MergeMapTest.php
+++ b/tests/Monoid/MergeMapTest.php
@@ -8,7 +8,7 @@
     Monoid,
     Map,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class MergeMapTest extends TestCase
 {
diff --git a/tests/Monoid/MergeSetTest.php b/tests/Monoid/MergeSetTest.php
index 0411677..877c627 100644
--- a/tests/Monoid/MergeSetTest.php
+++ b/tests/Monoid/MergeSetTest.php
@@ -8,7 +8,7 @@
     Monoid,
     Set,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class MergeSetTest extends TestCase
 {
diff --git a/tests/PairTest.php b/tests/PairTest.php
index 792afc6..7211714 100644
--- a/tests/PairTest.php
+++ b/tests/PairTest.php
@@ -4,7 +4,7 @@
 namespace Tests\Innmind\Immutable;
 
 use Innmind\Immutable\Pair;
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class PairTest extends TestCase
 {
diff --git a/tests/RegExpTest.php b/tests/RegExpTest.php
index b998653..ad1a6c4 100644
--- a/tests/RegExpTest.php
+++ b/tests/RegExpTest.php
@@ -7,9 +7,9 @@
     RegExp,
     Str,
     Map,
-    Exception\LogicException
+    Exception\LogicException,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class RegExpTest extends TestCase
 {
diff --git a/tests/Sequence/DeferTest.php b/tests/Sequence/DeferTest.php
index df87b43..a591b9c 100644
--- a/tests/Sequence/DeferTest.php
+++ b/tests/Sequence/DeferTest.php
@@ -12,7 +12,7 @@
     Set,
     SideEffect,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class DeferTest extends TestCase
 {
diff --git a/tests/Sequence/LazyTest.php b/tests/Sequence/LazyTest.php
index 619b73b..465bcde 100644
--- a/tests/Sequence/LazyTest.php
+++ b/tests/Sequence/LazyTest.php
@@ -12,7 +12,7 @@
     Set,
     SideEffect,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class LazyTest extends TestCase
 {
diff --git a/tests/Sequence/PrimitiveTest.php b/tests/Sequence/PrimitiveTest.php
index 263ce36..da3f75e 100644
--- a/tests/Sequence/PrimitiveTest.php
+++ b/tests/Sequence/PrimitiveTest.php
@@ -12,7 +12,7 @@
     Set,
     SideEffect,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class PrimitiveTest extends TestCase
 {
diff --git a/tests/SequenceTest.php b/tests/SequenceTest.php
index 414a74f..a7babe4 100644
--- a/tests/SequenceTest.php
+++ b/tests/SequenceTest.php
@@ -14,9 +14,9 @@
 };
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set as DataSet,
 };
-use PHPUnit\Framework\TestCase;
 
 class SequenceTest extends TestCase
 {
diff --git a/tests/Set/DeferTest.php b/tests/Set/DeferTest.php
index 94146f3..aa02f97 100644
--- a/tests/Set/DeferTest.php
+++ b/tests/Set/DeferTest.php
@@ -12,7 +12,7 @@
     Sequence,
     SideEffect,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class DeferTest extends TestCase
 {
diff --git a/tests/Set/LazyTest.php b/tests/Set/LazyTest.php
index 8aaa6fd..2612e66 100644
--- a/tests/Set/LazyTest.php
+++ b/tests/Set/LazyTest.php
@@ -12,7 +12,7 @@
     Sequence,
     SideEffect,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class LazyTest extends TestCase
 {
diff --git a/tests/Set/PrimitiveTest.php b/tests/Set/PrimitiveTest.php
index a4c8d86..d2d00f8 100644
--- a/tests/Set/PrimitiveTest.php
+++ b/tests/Set/PrimitiveTest.php
@@ -12,7 +12,7 @@
     Sequence,
     SideEffect,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class PrimitiveTest extends TestCase
 {
diff --git a/tests/SetTest.php b/tests/SetTest.php
index a454651..1418b61 100644
--- a/tests/SetTest.php
+++ b/tests/SetTest.php
@@ -10,7 +10,7 @@
     Sequence,
     Predicate,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class SetTest extends TestCase
 {
diff --git a/tests/StateTest.php b/tests/StateTest.php
index 7235194..647636c 100644
--- a/tests/StateTest.php
+++ b/tests/StateTest.php
@@ -7,9 +7,9 @@
     State,
     State\Result,
 };
-use PHPUnit\Framework\TestCase;
 use Innmind\BlackBox\{
     PHPUnit\BlackBox,
+    PHPUnit\Framework\TestCase,
     Set,
 };
 
diff --git a/tests/StrTest.php b/tests/StrTest.php
index 8e7a724..1490ea3 100644
--- a/tests/StrTest.php
+++ b/tests/StrTest.php
@@ -10,7 +10,7 @@
     Set,
     Exception\InvalidRegex,
 };
-use PHPUnit\Framework\TestCase;
+use Innmind\BlackBox\PHPUnit\Framework\TestCase;
 
 class StrTest extends TestCase
 {
@@ -23,7 +23,7 @@ public function testInterfaces()
 
     public function testOf()
     {
-        $str = S::of('foo', 'ASCII');
+        $str = S::of('foo', S\Encoding::ascii);
 
         $this->assertInstanceOf(S::class, $str);
         $this->assertSame('foo', $str->toString());
@@ -32,24 +32,20 @@ public function testOf()
 
     public function testEncoding()
     {
-        $this->assertInstanceOf(S::class, S::of('')->encoding());
-        $this->assertSame('UTF-8', S::of('')->encoding()->toString());
+        $this->assertSame(S\Encoding::utf8, S::of('')->encoding());
     }
 
     public function testToEncoding()
     {
         $str = S::of('foo🙏bar');
-        $str2 = $str->toEncoding('ASCII');
-        $str3 = $str->toEncoding(S\Encoding::ascii);
+        $str2 = $str->toEncoding(S\Encoding::ascii);
 
         $this->assertInstanceOf(S::class, $str2);
         $this->assertNotSame($str, $str2);
-        $this->assertSame('UTF-8', $str->encoding()->toString());
-        $this->assertSame('ASCII', $str2->encoding()->toString());
-        $this->assertSame('ASCII', $str3->encoding()->toString());
+        $this->assertSame(S\Encoding::utf8, $str->encoding());
+        $this->assertSame(S\Encoding::ascii, $str2->encoding());
         $this->assertSame(7, $str->length());
         $this->assertSame(10, $str2->length());
-        $this->assertSame(10, $str3->length());
     }
 
     public function testSplit()
@@ -68,14 +64,14 @@ public function testSplit()
         $this->assertSame('o', $this->get($sequence, 1)->toString());
         $this->assertSame('o', $this->get($sequence, 2)->toString());
 
-        $parts = S::of('🤩👍🤔', 'UTF-8')->split();
+        $parts = S::of('🤩👍🤔', S\Encoding::utf8)->split();
 
         $this->assertSame('🤩', $this->get($parts, 0)->toString());
         $this->assertSame('👍', $this->get($parts, 1)->toString());
         $this->assertSame('🤔', $this->get($parts, 2)->toString());
         $this->assertNotSame(
             '🤩',
-            $this->get(S::of('🤩👍🤔', 'ASCII')->split(), 0)->toString(),
+            $this->get(S::of('🤩👍🤔', S\Encoding::ascii)->split(), 0)->toString(),
         );
 
         $sequence = $str->split('');
@@ -127,7 +123,7 @@ public function testSplitUtf8ManipulatedAsAscii()
         $this->assertSame('a', $this->get($splits, 5)->toString());
         $this->assertSame('r', $this->get($splits, 6)->toString());
 
-        $splits = $str->toEncoding('ASCII')->split();
+        $splits = $str->toEncoding(S\Encoding::ascii)->split();
 
         $this->assertSame('f', $this->get($splits, 0)->toString());
         $this->assertSame('o', $this->get($splits, 1)->toString());
@@ -149,12 +145,12 @@ public function testSplitUtf8ManipulatedAsAsciiWithDelimiter()
         $this->assertSame('foo', $this->get($splits, 0)->toString());
         $this->assertSame('bar', $this->get($splits, 1)->toString());
 
-        $splits = $str->toEncoding('ASCII')->split('🙏');
+        $splits = $str->toEncoding(S\Encoding::ascii)->split('🙏');
 
         $this->assertSame('foo', $this->get($splits, 0)->toString());
         $this->assertSame('bar', $this->get($splits, 1)->toString());
 
-        $splits = $str->toEncoding('ASCII')->split(
+        $splits = $str->toEncoding(S\Encoding::ascii)->split(
             \mb_substr('🙏', 0, 1, 'ASCII'),
         );
 
@@ -182,7 +178,7 @@ public function testChunk()
     public function testChunkUtf8ManipulatedAsAscii()
     {
         $splits = S::of('foo🙏bar')
-            ->toEncoding('ASCII')
+            ->toEncoding(S\Encoding::ascii)
             ->chunk();
 
         $this->assertSame('f', $this->get($splits, 0)->toString());
@@ -197,7 +193,7 @@ public function testChunkUtf8ManipulatedAsAscii()
         $this->assertSame('r', $this->get($splits, 9)->toString());
 
         $splits = S::of('foo🙏bar')
-            ->toEncoding('ASCII')
+            ->toEncoding(S\Encoding::ascii)
             ->chunk(3);
 
         $this->assertSame('foo', $this->get($splits, 0)->toString());
@@ -249,7 +245,7 @@ public function testPosition()
         );
         $this->assertSame(
             7,
-            $emoji->toEncoding('ASCII')->position('bar')->match(
+            $emoji->toEncoding(S\Encoding::ascii)->position('bar')->match(
                 static fn($value) => $value,
                 static fn() => null,
             ),
@@ -301,7 +297,7 @@ public function testReplaceWithDifferentEncoding()
             $str2->toString(),
         );
 
-        $str3 = $str->toEncoding('ASCII')->replace(
+        $str3 = $str->toEncoding(S\Encoding::ascii)->replace(
             \mb_substr('🙏', 0, 1, 'ASCII'),
             'baz',
         );
@@ -340,14 +336,14 @@ public function testToLower()
     public function testLength()
     {
         $this->assertSame(4, S::of('foo🙏')->length());
-        $this->assertSame(7, S::of('foo🙏')->toEncoding('ASCII')->length());
+        $this->assertSame(7, S::of('foo🙏')->toEncoding(S\Encoding::ascii)->length());
     }
 
     public function testEmpty()
     {
         $this->assertTrue(S::of('')->empty());
         $this->assertFalse(S::of('🙏')->empty());
-        $this->assertFalse(S::of('🙏', 'ASCII')->substring(0, 1)->empty());
+        $this->assertFalse(S::of('🙏', S\Encoding::ascii)->substring(0, 1)->empty());
     }
 
     public function testReverse()
@@ -361,7 +357,7 @@ public function testReverse()
         $this->assertSame('foo🙏', $str->toString());
         $this->assertSame(
             \strrev('🙏').'oof',
-            $str->toEncoding('ASCII')->reverse()->toString(),
+            $str->toEncoding(S\Encoding::ascii)->reverse()->toString(),
         );
     }
 
@@ -373,7 +369,7 @@ public function testReverseKeepTheGivenEncoding()
         );
         $this->assertSame(
             'ASCII',
-            S::of('foo', 'ASCII')->reverse()->encoding()->toString(),
+            S::of('foo', S\Encoding::ascii)->reverse()->encoding()->toString(),
         );
     }
 
@@ -413,7 +409,7 @@ public function testRepeat()
         $this->assertSame('foofoofoo', $str2->toString());
         $this->assertSame('foo', $str->toString());
         $this->assertSame('🙏🙏', S::of('🙏')->repeat(2)->toString());
-        $this->assertSame('🙏🙏', S::of('🙏')->toEncoding('ASCII')->repeat(2)->toString());
+        $this->assertSame('🙏🙏', S::of('🙏')->toEncoding(S\Encoding::ascii)->repeat(2)->toString());
     }
 
     public function testStripSlashes()
@@ -511,7 +507,7 @@ public function testMatches()
         $this->assertTrue($str->matches('/^abc/'));
 
         $this->assertTrue(S::of('foo🙏bar')->matches('/🙏/'));
-        $this->assertTrue(S::of('foo🙏bar')->toEncoding('ASCII')->matches('/🙏/'));
+        $this->assertTrue(S::of('foo🙏bar')->toEncoding(S\Encoding::ascii)->matches('/🙏/'));
         $this->assertTrue(S::of('foo🙏bar')->matches(S::of('/🙏/')));
     }
 
@@ -636,7 +632,7 @@ public function testDropEnd()
 
     public function testSubstringUtf8ManipulatedAsAscii()
     {
-        $str = S::of('foo🙏bar')->toEncoding('ASCII');
+        $str = S::of('foo🙏bar')->toEncoding(S\Encoding::ascii);
 
         $this->assertSame('🙏bar', $str->substring(3)->toString());
         $this->assertSame('🙏', $str->substring(3, 4)->toString());
@@ -817,7 +813,7 @@ public function testMap()
         $a = S::of('foo');
         $b = $a->map(function($string, $encoding) use ($a) {
             $this->assertSame('foo', $string);
-            $this->assertSame($a->encoding()->toString(), $encoding);
+            $this->assertSame($a->encoding(), $encoding);
 
             return 'bar';
         });
@@ -833,7 +829,7 @@ public function testFlatMap()
         $a = S::of('foo');
         $b = $a->flatMap(function($string, $encoding) use ($a, $expected) {
             $this->assertSame('foo', $string);
-            $this->assertSame($a->encoding()->toString(), $encoding);
+            $this->assertSame($a->encoding(), $encoding);
 
             return $expected;
         });