diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
new file mode 100644
index 0000000..bf88843
--- /dev/null
+++ b/.github/workflows/tests.yml
@@ -0,0 +1,53 @@
+on: [pull_request]
+name: PHPUnit
+
+jobs:
+  tests:
+    name: Tests
+    runs-on: Ubuntu-20.04
+
+    strategy:
+      matrix:
+        include:
+          # Lowest deps (PHP 8.1 & sf 6.4)
+          - php: 8.1
+            symfony-require: 6.4.*
+            composer-flags: '--prefer-stable --prefer-lowest'
+          # Normal deps with different php versions
+          - php: 8.2
+            symfony-require: 7.0.*
+            composer-flags: '--prefer-stable'
+          - php: 8.3
+            symfony-require: 7.0.*
+            composer-flags: '--prefer-stable'
+          # Development release
+          - php: nightly
+            symfony-require: 7.1.*@dev
+            stability: dev
+            can-fail: true
+      fail-fast: false
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: none
+
+      - name: Configure Composer minimum stability
+        if: matrix.stability
+        run: composer config minimum-stability ${{ matrix.stability }}
+
+      - name: Install dependencies
+        env:
+          SYMFONY_REQUIRE: ${{ matrix.symfony-require }}
+        run: composer update ${{ matrix.composer-flags }} --no-interaction --no-progress --optimize-autoloader
+
+      - name: Run PHPUnit
+        env:
+          HELLOASSO_CLIENT_ID: ${{ secrets.TESTS_HELLOASSO_ID }}
+          HELLOASSO_CLIENT_SECRET: ${{ secrets.TESTS_HELLOASSO_SECRET }}
+        run: vendor/bin/phpunit
diff --git a/.gitignore b/.gitignore
index b33fdab..399b9fb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -5,3 +5,4 @@ composer.lock
 
 /tools/*/composer.lock
 /tools/*/vendor
+/.phpunit.cache
diff --git a/composer.json b/composer.json
index e3b5e92..a8d3d94 100644
--- a/composer.json
+++ b/composer.json
@@ -23,10 +23,18 @@
             "Helloasso\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "Helloasso\\Tests\\": "tests/"
+        }
+    },
     "authors": [
         {
             "name": "Doskyft",
             "email": "doskyft@gmail.com"
         }
-    ]
+    ],
+    "require-dev": {
+        "phpunit/phpunit": "^10.5"
+    }
 }
diff --git a/phpstan.neon b/phpstan.neon
index f5ab67f..8edd531 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -5,3 +5,4 @@ parameters:
     level: 5
     paths:
       - src
+      - tests
diff --git a/phpunit.xml b/phpunit.xml
new file mode 100644
index 0000000..5f79d00
--- /dev/null
+++ b/phpunit.xml
@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/10.5/phpunit.xsd"
+         bootstrap="vendor/autoload.php"
+         cacheDirectory=".phpunit.cache"
+         executionOrder="depends,defects"
+         beStrictAboutOutputDuringTests="true"
+         failOnRisky="true"
+         failOnWarning="true">
+    <testsuites>
+        <testsuite name="default">
+            <directory>tests</directory>
+        </testsuite>
+    </testsuites>
+
+    <source restrictDeprecations="true" restrictNotices="true" restrictWarnings="true">
+        <include>
+            <directory>src</directory>
+        </include>
+    </source>
+</phpunit>
diff --git a/tests/Functional/Service/CheckoutIntentServiceTest.php b/tests/Functional/Service/CheckoutIntentServiceTest.php
new file mode 100644
index 0000000..1eedcd9
--- /dev/null
+++ b/tests/Functional/Service/CheckoutIntentServiceTest.php
@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Helloasso\Tests\Functional\Service;
+
+use Helloasso\Models\Carts\CheckoutPayer;
+use Helloasso\Models\Carts\InitCheckoutBody;
+use Helloasso\Models\Carts\InitCheckoutResponse;
+use Helloasso\Service\CheckoutIntentService;
+
+final class CheckoutIntentServiceTest extends ServiceTestCase
+{
+    public function testCreate(): void
+    {
+        $service = $this->createService(CheckoutIntentService::class);
+
+        $payer = new CheckoutPayer();
+        $payer
+            ->setFirstName('Greta')
+            ->setLastName('Thunberg')
+            ->setDateOfBirth(new \DateTimeImmutable('-20 years'))
+        ;
+
+        $body = new InitCheckoutBody();
+        $body
+            ->setItemName('Awesome product')
+            ->setInitialAmount(4200)
+            ->setTotalAmount(4200)
+            ->setBackUrl('https://my-app.fr/back_url')
+            ->setReturnUrl('https://my-app.fr/return_url')
+            ->setErrorUrl('https://my-app.fr/error_url')
+            ->setPayer($payer)
+        ;
+
+        $response = $service->create($body);
+
+        $this->assertInstanceOf(InitCheckoutResponse::class, $response);
+    }
+}
diff --git a/tests/Functional/Service/ServiceTestCase.php b/tests/Functional/Service/ServiceTestCase.php
new file mode 100644
index 0000000..131940d
--- /dev/null
+++ b/tests/Functional/Service/ServiceTestCase.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Helloasso\Tests\Functional\Service;
+
+use Helloasso\Service\ApiRequest;
+use PHPUnit\Framework\TestCase;
+
+abstract class ServiceTestCase extends TestCase
+{
+    /**
+     * @template T of ApiRequest
+     *
+     * @param class-string<T> $className
+     *
+     * @return T
+     */
+    protected function createService(string $className): ApiRequest
+    {
+        $clientId = getenv('HELLOASSO_CLIENT_ID');
+        $clientSecret = getenv('HELLOASSO_CLIENT_SECRET');
+        $organisationSlug = getenv('HELLOASSO_ORGANISATION') ? getenv('HELLOASSO_ORGANISATION_SLUG') : 'helloasso-php-sdk';
+
+        if (false === $clientId || false === $clientSecret) {
+            throw new \RuntimeException('Some mandatory environment variables ("HELLOASSO_CLIENT_ID", "HELLOASSO_CLIENT_SECRET") have not been set. Please consider creating an account on https://www.helloasso-sandbox.com/ and run tests using HELLOASSO_CLIENT_ID=[YourClientId] HELLOASSO_CLIENT_SECRET=[YourClientSecret] HELLOASSO_ORGANISATION_SLUG=[YourOrganisation] vendor/bin/phpunit');
+        }
+
+        return new $className($clientId, $clientSecret, $organisationSlug, true);
+    }
+}