diff --git a/tests/Unit/Service/ContributionAggregatorTest.php b/tests/Unit/Service/ContributionAggregatorTest.php
new file mode 100644
index 0000000..95f1d8f
--- /dev/null
+++ b/tests/Unit/Service/ContributionAggregatorTest.php
@@ -0,0 +1,109 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\ContributionAggregator;
+use App\Service\ProviderInterface;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+
+#[CoversClass(ContributionAggregator::class)]
+final class ContributionAggregatorTest extends TestCase
+{
+    private LoggerInterface $logger;
+
+    protected function setUp(): void
+    {
+        $this->logger = $this->createStub(LoggerInterface::class);
+    }
+
+    #[Test]
+    public function it_returns_empty_array_when_no_providers_are_given(): void
+    {
+        $aggregator = new ContributionAggregator([], $this->logger);
+
+        $result = $aggregator->aggregate();
+
+        $this->assertSame([], $result);
+    }
+
+    #[Test]
+    public function it_skips_unconfigured_providers(): void
+    {
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('isConfigured')->willReturn(false);
+
+        $aggregator = new ContributionAggregator([$provider], $this->logger);
+
+        $result = $aggregator->aggregate();
+
+        $this->assertSame([], $result);
+    }
+
+    #[Test]
+    public function it_returns_contributions_from_a_configured_provider(): void
+    {
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('isConfigured')->willReturn(true);
+        $provider->method('fetch')->willReturn(['2024-01-01' => 3]);
+
+        $aggregator = new ContributionAggregator([$provider], $this->logger);
+
+        $result = $aggregator->aggregate();
+
+        $this->assertSame(['2024-01-01' => 3], $result);
+    }
+
+    #[Test]
+    public function it_sums_contributions_from_multiple_providers_on_the_same_date(): void
+    {
+        $providerA = $this->createStub(ProviderInterface::class);
+        $providerA->method('isConfigured')->willReturn(true);
+        $providerA->method('fetch')->willReturn(['2024-01-01' => 3, '2024-01-02' => 1]);
+
+        $providerB = $this->createStub(ProviderInterface::class);
+        $providerB->method('isConfigured')->willReturn(true);
+        $providerB->method('fetch')->willReturn(['2024-01-01' => 2, '2024-01-03' => 5]);
+
+        $aggregator = new ContributionAggregator([$providerA, $providerB], $this->logger);
+
+        $result = $aggregator->aggregate();
+
+        $this->assertSame(['2024-01-01' => 5, '2024-01-02' => 1, '2024-01-03' => 5], $result);
+    }
+
+    #[Test]
+    public function it_continues_fetching_remaining_providers_when_one_throws(): void
+    {
+        $failing = $this->createStub(ProviderInterface::class);
+        $failing->method('isConfigured')->willReturn(true);
+        $failing->method('fetch')->willThrowException(new \RuntimeException('Network error'));
+
+        $healthy = $this->createStub(ProviderInterface::class);
+        $healthy->method('isConfigured')->willReturn(true);
+        $healthy->method('fetch')->willReturn(['2024-01-01' => 7]);
+
+        $aggregator = new ContributionAggregator([$failing, $healthy], $this->logger);
+
+        $result = $aggregator->aggregate();
+
+        $this->assertSame(['2024-01-01' => 7], $result);
+    }
+
+    #[Test]
+    public function it_logs_a_warning_when_a_provider_fetch_throws(): void
+    {
+        $logger = $this->createMock(LoggerInterface::class);
+        $logger->expects($this->once())->method('warning');
+
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('isConfigured')->willReturn(true);
+        $provider->method('fetch')->willThrowException(new \RuntimeException('fail'));
+
+        (new ContributionAggregator([$provider], $logger))->aggregate();
+    }
+}
diff --git a/tests/Unit/Service/GitHubProviderTest.php b/tests/Unit/Service/GitHubProviderTest.php
new file mode 100644
index 0000000..daeace5
--- /dev/null
+++ b/tests/Unit/Service/GitHubProviderTest.php
@@ -0,0 +1,146 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\GitHubProvider;
+use IDCI\Bundle\GraphQLClientBundle\Client\GraphQLApiClient;
+use IDCI\Bundle\GraphQLClientBundle\Client\GraphQLApiClientRegistryInterface;
+use IDCI\Bundle\GraphQLClientBundle\Query\GraphQLQuery;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\HttpKernel\Exception\ServiceUnavailableHttpException;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+use Symfony\Contracts\HttpClient\ResponseInterface;
+
+#[CoversClass(GitHubProvider::class)]
+final class GitHubProviderTest extends TestCase
+{
+    private function makeProvider(
+        string $username = 'user',
+        string $token = 'token',
+        ?HttpClientInterface $client = null,
+        ?GraphQLApiClientRegistryInterface $registry = null,
+    ): GitHubProvider {
+        if ($registry === null) {
+            $graphqlQuery = $this->createStub(GraphQLQuery::class);
+            $graphqlQuery->method('getGraphQLQuery')->willReturn('query {}');
+
+            $graphqlClient = $this->createStub(GraphQLApiClient::class);
+            $graphqlClient->method('buildQuery')->willReturn($graphqlQuery);
+
+            $registry = $this->createStub(GraphQLApiClientRegistryInterface::class);
+            $registry->method('get')->willReturn($graphqlClient);
+        }
+
+        return new GitHubProvider(
+            $client ?? $this->createStub(HttpClientInterface::class),
+            $registry,
+            $username,
+            $token,
+            $this->createStub(LoggerInterface::class),
+        );
+    }
+
+    private function stubGraphqlResponse(array $weeks): ResponseInterface
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('toArray')->willReturn([
+            'data' => [
+                'user' => [
+                    'contributionsCollection' => [
+                        'contributionCalendar' => ['weeks' => $weeks],
+                    ],
+                ],
+            ],
+        ]);
+
+        return $response;
+    }
+
+    #[Test]
+    public function it_returns_github_as_name(): void
+    {
+        $this->assertSame('github', $this->makeProvider()->getName());
+    }
+
+    #[Test]
+    public function it_is_configured_when_credentials_are_set(): void
+    {
+        $this->assertTrue($this->makeProvider()->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_username_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(username: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_token_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(token: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_parses_contribution_days_from_the_graphql_response(): void
+    {
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubGraphqlResponse([
+            ['contributionDays' => [
+                ['date' => '2024-06-10', 'contributionCount' => 4],
+                ['date' => '2024-06-11', 'contributionCount' => 2],
+            ]],
+        ]));
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame(4, $result['2024-06-10']);
+        $this->assertSame(2, $result['2024-06-11']);
+    }
+
+    #[Test]
+    public function it_skips_days_with_zero_contributions(): void
+    {
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubGraphqlResponse([
+            ['contributionDays' => [
+                ['date' => '2024-06-11', 'contributionCount' => 0],
+            ]],
+        ]));
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertArrayNotHasKey('2024-06-11', $result);
+    }
+
+    #[Test]
+    public function it_throws_service_unavailable_exception_on_graphql_errors(): void
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('toArray')->willReturn([
+            'errors' => [['message' => 'Bad credentials']],
+        ]);
+
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($response);
+
+        $this->expectException(ServiceUnavailableHttpException::class);
+
+        $this->makeProvider(client: $client)->fetch();
+    }
+
+    #[Test]
+    public function it_returns_empty_when_response_has_no_weeks(): void
+    {
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubGraphqlResponse([]));
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame([], $result);
+    }
+}
diff --git a/tests/Unit/Service/GitLabProviderTest.php b/tests/Unit/Service/GitLabProviderTest.php
new file mode 100644
index 0000000..5e09aa7
--- /dev/null
+++ b/tests/Unit/Service/GitLabProviderTest.php
@@ -0,0 +1,128 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\GitLabProvider;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+use Symfony\Contracts\HttpClient\ResponseInterface;
+
+#[CoversClass(GitLabProvider::class)]
+final class GitLabProviderTest extends TestCase
+{
+    private function makeProvider(
+        string $username = 'user',
+        string $token = 'token',
+        string $baseUrl = '',
+        ?HttpClientInterface $client = null,
+    ): GitLabProvider {
+        return new GitLabProvider(
+            $client ?? $this->createStub(HttpClientInterface::class),
+            $username,
+            $token,
+            $this->createStub(LoggerInterface::class),
+            $baseUrl,
+        );
+    }
+
+    private function stubResponse(array $data): ResponseInterface
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('toArray')->willReturn($data);
+
+        return $response;
+    }
+
+    #[Test]
+    public function it_returns_gitlab_as_name(): void
+    {
+        $this->assertSame('gitlab', $this->makeProvider()->getName());
+    }
+
+    #[Test]
+    public function it_is_configured_when_credentials_are_set(): void
+    {
+        $this->assertTrue($this->makeProvider()->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_username_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(username: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_token_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(token: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_throws_not_found_exception_when_user_does_not_exist(): void
+    {
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubResponse([]));
+
+        $this->expectException(NotFoundHttpException::class);
+
+        $this->makeProvider(client: $client)->fetch();
+    }
+
+    #[Test]
+    public function it_fetches_events_and_counts_them_by_date(): void
+    {
+        $client = $this->createMock(HttpClientInterface::class);
+        $client->method('request')->willReturnCallback(
+            function (string $method, string $url): ResponseInterface {
+                if (str_contains($url, '/events')) {
+                    return $this->stubResponse([
+                        ['created_at' => '2024-06-10T12:00:00.000Z'],
+                        ['created_at' => '2024-06-10T14:00:00.000Z'],
+                        ['created_at' => '2024-06-11T08:00:00.000Z'],
+                    ]);
+                }
+
+                return $this->stubResponse([['id' => 42]]);
+            }
+        );
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame(2, $result['2024-06-10']);
+        $this->assertSame(1, $result['2024-06-11']);
+    }
+
+    #[Test]
+    public function it_fetches_multiple_pages_until_page_has_fewer_than_100_events(): void
+    {
+        $callCount = 0;
+
+        $client = $this->createMock(HttpClientInterface::class);
+        $client->method('request')->willReturnCallback(
+            function (string $method, string $url) use (&$callCount): ResponseInterface {
+                if (!str_contains($url, '/events')) {
+                    return $this->stubResponse([['id' => 42]]);
+                }
+
+                $callCount++;
+                $data = $callCount === 1
+                    ? array_fill(0, 100, ['created_at' => '2024-06-10T12:00:00.000Z'])
+                    : [['created_at' => '2024-06-11T08:00:00.000Z']];
+
+                return $this->stubResponse($data);
+            }
+        );
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame(2, $callCount);
+        $this->assertSame(100, $result['2024-06-10']);
+        $this->assertSame(1, $result['2024-06-11']);
+    }
+}
diff --git a/tests/Unit/Service/GiteaProviderTest.php b/tests/Unit/Service/GiteaProviderTest.php
new file mode 100644
index 0000000..9593f29
--- /dev/null
+++ b/tests/Unit/Service/GiteaProviderTest.php
@@ -0,0 +1,111 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\GiteaProvider;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Psr\Log\LoggerInterface;
+use Symfony\Contracts\HttpClient\HttpClientInterface;
+use Symfony\Contracts\HttpClient\ResponseInterface;
+
+#[CoversClass(GiteaProvider::class)]
+final class GiteaProviderTest extends TestCase
+{
+    private function makeProvider(
+        string $username = 'user',
+        string $token = 'token',
+        string $baseUrl = 'https://gitea.example.com',
+        ?HttpClientInterface $client = null,
+    ): GiteaProvider {
+        return new GiteaProvider(
+            $client ?? $this->createStub(HttpClientInterface::class),
+            $username,
+            $token,
+            $baseUrl,
+            $this->createStub(LoggerInterface::class),
+        );
+    }
+
+    private function stubResponse(array $data): ResponseInterface
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('toArray')->willReturn($data);
+
+        return $response;
+    }
+
+    #[Test]
+    public function it_returns_gitea_as_name(): void
+    {
+        $this->assertSame('gitea', $this->makeProvider()->getName());
+    }
+
+    #[Test]
+    public function it_is_configured_when_all_credentials_are_set(): void
+    {
+        $this->assertTrue($this->makeProvider()->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_username_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(username: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_token_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(token: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_is_not_configured_when_base_url_is_empty(): void
+    {
+        $this->assertFalse($this->makeProvider(baseUrl: '')->isConfigured());
+    }
+
+    #[Test]
+    public function it_parses_heatmap_entries_into_contributions(): void
+    {
+        $now = time();
+
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubResponse([
+            ['timestamp' => $now, 'contributions' => 5],
+        ]));
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame(5, $result[date('Y-m-d', $now)]);
+    }
+
+    #[Test]
+    public function it_filters_out_entries_older_than_365_days(): void
+    {
+        $old = (new \DateTimeImmutable('-366 days'))->getTimestamp();
+
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubResponse([
+            ['timestamp' => $old, 'contributions' => 3],
+        ]));
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame([], $result);
+    }
+
+    #[Test]
+    public function it_returns_empty_when_response_has_no_entries(): void
+    {
+        $client = $this->createStub(HttpClientInterface::class);
+        $client->method('request')->willReturn($this->stubResponse([]));
+
+        $result = $this->makeProvider(client: $client)->fetch();
+
+        $this->assertSame([], $result);
+    }
+}
diff --git a/tests/Unit/Service/ProbeTraitTest.php b/tests/Unit/Service/ProbeTraitTest.php
new file mode 100644
index 0000000..64b5a28
--- /dev/null
+++ b/tests/Unit/Service/ProbeTraitTest.php
@@ -0,0 +1,128 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\ProbeTrait;
+use App\Service\ProviderErrorCode;
+use App\Service\ProviderInterface;
+use App\Service\ProviderStatusType;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Symfony\Contracts\HttpClient\Exception\ClientExceptionInterface;
+use Symfony\Contracts\HttpClient\Exception\TransportExceptionInterface;
+use Symfony\Contracts\HttpClient\ResponseInterface;
+
+#[CoversClass(ProbeTrait::class)]
+final class ProbeTraitTest extends TestCase
+{
+    private function makeProvider(bool $configured, \Closure $ping): ProviderInterface
+    {
+        return new class($configured, $ping) implements ProviderInterface {
+            use ProbeTrait;
+
+            public function __construct(
+                private bool $configured,
+                private \Closure $ping,
+            ) {}
+
+            public function isConfigured(): bool { return $this->configured; }
+            public function getName(): string { return 'test'; }
+            public function ping(): void { ($this->ping)(); }
+            public function fetch(): array { return []; }
+        };
+    }
+
+    #[Test]
+    public function it_returns_not_configured_when_provider_is_not_configured(): void
+    {
+        $provider = $this->makeProvider(false, fn() => null);
+
+        $status = $provider->probe();
+
+        $this->assertSame(ProviderStatusType::NotConfigured, $status->status);
+        $this->assertNull($status->error);
+    }
+
+    #[Test]
+    public function it_returns_ok_when_ping_succeeds(): void
+    {
+        $provider = $this->makeProvider(true, fn() => null);
+
+        $status = $provider->probe();
+
+        $this->assertSame(ProviderStatusType::Ok, $status->status);
+        $this->assertNull($status->error);
+    }
+
+    #[Test]
+    public function it_returns_url_unreachable_on_transport_failure(): void
+    {
+        $exception = $this->createStub(TransportExceptionInterface::class);
+        $provider  = $this->makeProvider(true, fn() => throw $exception);
+
+        $status = $provider->probe();
+
+        $this->assertSame(ProviderStatusType::Error, $status->status);
+        $this->assertSame(ProviderErrorCode::UrlUnreachable, $status->error);
+    }
+
+    #[Test]
+    public function it_returns_auth_failed_on_401(): void
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(401);
+
+        $exception = $this->createStub(ClientExceptionInterface::class);
+        $exception->method('getResponse')->willReturn($response);
+
+        $status = $this->makeProvider(true, fn() => throw $exception)->probe();
+
+        $this->assertSame(ProviderStatusType::Error, $status->status);
+        $this->assertSame(ProviderErrorCode::AuthFailed, $status->error);
+    }
+
+    #[Test]
+    public function it_returns_auth_failed_on_403(): void
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(403);
+
+        $exception = $this->createStub(ClientExceptionInterface::class);
+        $exception->method('getResponse')->willReturn($response);
+
+        $status = $this->makeProvider(true, fn() => throw $exception)->probe();
+
+        $this->assertSame(ProviderStatusType::Error, $status->status);
+        $this->assertSame(ProviderErrorCode::AuthFailed, $status->error);
+    }
+
+    #[Test]
+    public function it_returns_url_unreachable_on_404(): void
+    {
+        $response = $this->createStub(ResponseInterface::class);
+        $response->method('getStatusCode')->willReturn(404);
+
+        $exception = $this->createStub(ClientExceptionInterface::class);
+        $exception->method('getResponse')->willReturn($response);
+
+        $status = $this->makeProvider(true, fn() => throw $exception)->probe();
+
+        $this->assertSame(ProviderStatusType::Error, $status->status);
+        $this->assertSame(ProviderErrorCode::UrlUnreachable, $status->error);
+    }
+
+    #[Test]
+    public function it_returns_unknown_error_on_unexpected_exception(): void
+    {
+        $provider = $this->makeProvider(true, fn() => throw new \RuntimeException('Something went wrong'));
+
+        $status = $provider->probe();
+
+        $this->assertSame(ProviderStatusType::Error, $status->status);
+        $this->assertSame(ProviderErrorCode::Unknown, $status->error);
+        $this->assertSame('Something went wrong', $status->message);
+    }
+}
diff --git a/tests/Unit/Service/ProviderHealthCheckerTest.php b/tests/Unit/Service/ProviderHealthCheckerTest.php
new file mode 100644
index 0000000..ebda929
--- /dev/null
+++ b/tests/Unit/Service/ProviderHealthCheckerTest.php
@@ -0,0 +1,88 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\ProviderErrorCode;
+use App\Service\ProviderHealthChecker;
+use App\Service\ProviderInterface;
+use App\Service\ProviderStatus;
+use App\Service\ProviderStatusType;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(ProviderHealthChecker::class)]
+final class ProviderHealthCheckerTest extends TestCase
+{
+    #[Test]
+    public function it_returns_ok_when_all_providers_are_healthy(): void
+    {
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('probe')->willReturn(new ProviderStatus('test', ProviderStatusType::Ok));
+
+        $result = (new ProviderHealthChecker([$provider]))->check();
+
+        $this->assertSame('ok', $result['status']);
+    }
+
+    #[Test]
+    public function it_returns_degraded_when_a_provider_has_an_error(): void
+    {
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('probe')->willReturn(
+            new ProviderStatus('test', ProviderStatusType::Error, ProviderErrorCode::AuthFailed, 'Invalid token'),
+        );
+
+        $result = (new ProviderHealthChecker([$provider]))->check();
+
+        $this->assertSame('degraded', $result['status']);
+    }
+
+    #[Test]
+    public function it_does_not_degrade_when_a_provider_is_not_configured(): void
+    {
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('probe')->willReturn(new ProviderStatus('test', ProviderStatusType::NotConfigured));
+
+        $result = (new ProviderHealthChecker([$provider]))->check();
+
+        $this->assertSame('ok', $result['status']);
+    }
+
+    #[Test]
+    public function it_indexes_provider_statuses_by_name(): void
+    {
+        $provider = $this->createStub(ProviderInterface::class);
+        $provider->method('probe')->willReturn(new ProviderStatus('github', ProviderStatusType::Ok));
+
+        $result = (new ProviderHealthChecker([$provider]))->check();
+
+        $this->assertArrayHasKey('github', $result['providers']);
+    }
+
+    #[Test]
+    public function it_returns_ok_with_no_providers(): void
+    {
+        $result = (new ProviderHealthChecker([]))->check();
+
+        $this->assertSame('ok', $result['status']);
+        $this->assertSame([], $result['providers']);
+    }
+
+    #[Test]
+    public function it_includes_all_provider_statuses_in_output(): void
+    {
+        $github = $this->createStub(ProviderInterface::class);
+        $github->method('probe')->willReturn(new ProviderStatus('github', ProviderStatusType::Ok));
+
+        $gitlab = $this->createStub(ProviderInterface::class);
+        $gitlab->method('probe')->willReturn(new ProviderStatus('gitlab', ProviderStatusType::NotConfigured));
+
+        $result = (new ProviderHealthChecker([$github, $gitlab]))->check();
+
+        $this->assertArrayHasKey('github', $result['providers']);
+        $this->assertArrayHasKey('gitlab', $result['providers']);
+    }
+}
diff --git a/tests/Unit/Service/ProviderStatusTest.php b/tests/Unit/Service/ProviderStatusTest.php
new file mode 100644
index 0000000..9ff6119
--- /dev/null
+++ b/tests/Unit/Service/ProviderStatusTest.php
@@ -0,0 +1,64 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Service;
+
+use App\Service\ProviderErrorCode;
+use App\Service\ProviderStatus;
+use App\Service\ProviderStatusType;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(ProviderStatus::class)]
+final class ProviderStatusTest extends TestCase
+{
+    #[Test]
+    public function it_serializes_ok_status(): void
+    {
+        $status = new ProviderStatus('github', ProviderStatusType::Ok);
+
+        $this->assertSame(['status' => 'ok'], $status->toArray());
+    }
+
+    #[Test]
+    public function it_serializes_not_configured_status(): void
+    {
+        $status = new ProviderStatus('github', ProviderStatusType::NotConfigured);
+
+        $this->assertSame(['status' => 'not_configured'], $status->toArray());
+    }
+
+    #[Test]
+    public function it_serializes_error_status_with_code_and_message(): void
+    {
+        $status = new ProviderStatus('github', ProviderStatusType::Error, ProviderErrorCode::AuthFailed, 'Token expired');
+
+        $this->assertSame([
+            'status'  => 'error',
+            'error'   => 'auth_failed',
+            'message' => 'Token expired',
+        ], $status->toArray());
+    }
+
+    #[Test]
+    public function it_omits_null_error_fields_from_array(): void
+    {
+        $status = new ProviderStatus('github', ProviderStatusType::Ok);
+
+        $array = $status->toArray();
+
+        $this->assertArrayNotHasKey('error', $array);
+        $this->assertArrayNotHasKey('message', $array);
+    }
+
+    #[Test]
+    public function it_exposes_typed_status_property(): void
+    {
+        $status = new ProviderStatus('github', ProviderStatusType::Error, ProviderErrorCode::Unknown, 'msg');
+
+        $this->assertSame(ProviderStatusType::Error, $status->status);
+        $this->assertSame(ProviderErrorCode::Unknown, $status->error);
+    }
+}