Implemented /metrics endpoint and reimplemented /stats

closes #418 (/metrics endpoint)

Usage:
```yaml
scrape_configs:
  - job_name: 'engelsystem'
    static_configs:
    - targets: ['engelsystem.example.com:80']
```

9 files changed, 725 insertions, 52 deletions

diff --git a/config/routes.php b/config/routes.php
index 2267bc88..8322cb2f 100644
--- a/config/routes.php
+++ b/config/routes.php
@@ -4,4 +4,9 @@ use FastRoute\RouteCollector;
 
 /** @var RouteCollector $route */
 
+// Pages
 $route->get('/credits', 'CreditsController@index');
+
+// Stats
+$route->get('/metrics', 'Metrics\\Controller@metrics');
+$route->get('/stats', 'Metrics\\Controller@stats');
diff --git a/includes/pages/guest_stats.php b/includes/pages/guest_stats.php
deleted file mode 100644
index d9012748..00000000
--- a/includes/pages/guest_stats.php
+++ /dev/null
@@ -1,47 +0,0 @@
-<?php
-
-use Engelsystem\Database\DB;
-use Engelsystem\Models\User\State;
-use Engelsystem\Models\User\User;
-
-function guest_stats()
-{
-    $apiKey = config('api_key');
-    $request = request();
-
-    if ($request->has('api_key')) {
-        if (!empty($apiKey) && $request->input('api_key') == $apiKey) {
-            $stats = [];
-
-            $stats['user_count'] = User::all()->count();
-            $stats['arrived_user_count'] = State::whereArrived(true)->count();
-
-            $done_shifts_seconds = DB::selectOne('
-                SELECT SUM(`Shifts`.`end` - `Shifts`.`start`)
-                FROM `ShiftEntry`
-                JOIN `Shifts` USING (`SID`)
-                WHERE `Shifts`.`end` < UNIX_TIMESTAMP()
-            ');
-            $done_shifts_seconds = (int)array_shift($done_shifts_seconds);
-            $stats['done_work_hours'] = round($done_shifts_seconds / (60 * 60), 0);
-
-            $users_in_action = DB::select('
-                SELECT `Shifts`.`start`, `Shifts`.`end`
-                FROM `ShiftEntry`
-                JOIN `Shifts` ON `Shifts`.`SID`=`ShiftEntry`.`SID`
-                WHERE UNIX_TIMESTAMP() BETWEEN `Shifts`.`start` AND `Shifts`.`end`
-            ');
-            $stats['users_in_action'] = count($users_in_action);
-
-            header('Content-Type: application/json');
-            raw_output(json_encode($stats));
-            return;
-        }
-        raw_output(json_encode([
-            'error' => 'Wrong api_key.'
-        ]));
-    }
-    raw_output(json_encode([
-        'error' => 'Missing parameter api_key.'
-    ]));
-}
diff --git a/src/Controllers/Metrics/Controller.php b/src/Controllers/Metrics/Controller.php
new file mode 100644
index 00000000..01fe1d6a
--- /dev/null
+++ b/src/Controllers/Metrics/Controller.php
@@ -0,0 +1,131 @@
+<?php
+
+namespace Engelsystem\Controllers\Metrics;
+
+use Engelsystem\Config\Config;
+use Engelsystem\Controllers\BaseController;
+use Engelsystem\Http\Exceptions\HttpForbidden;
+use Engelsystem\Http\Request;
+use Engelsystem\Http\Response;
+
+class Controller extends BaseController
+{
+    /** @var Config */
+    protected $config;
+
+    /** @var MetricsEngine */
+    protected $engine;
+
+    /** @var Request */
+    protected $request;
+
+    /** @var Response */
+    protected $response;
+
+    /** @var Stats */
+    protected $stats;
+
+    /**
+     * @param Response      $response
+     * @param MetricsEngine $engine
+     * @param Config        $config
+     * @param Request       $request
+     * @param Stats         $stats
+     */
+    public function __construct(
+        Response $response,
+        MetricsEngine $engine,
+        Config $config,
+        Request $request,
+        Stats $stats
+    ) {
+        $this->config = $config;
+        $this->engine = $engine;
+        $this->request = $request;
+        $this->response = $response;
+        $this->stats = $stats;
+    }
+
+    /**
+     * @return Response
+     */
+    public function metrics()
+    {
+        $now = microtime(true);
+        $this->checkAuth();
+
+        $data = [
+            $this->config->get('app_name') . ' stats',
+            'users'                => [
+                'type' => 'gauge',
+                ['labels' => ['state' => 'incoming'], 'value' => $this->stats->newUsers()],
+                ['labels' => ['state' => 'arrived', 'working' => 'no'], 'value' => $this->stats->arrivedUsers(false)],
+                ['labels' => ['state' => 'arrived', 'working' => 'yes'], 'value' => $this->stats->arrivedUsers(true)],
+            ],
+            'users_working'        => [
+                'type' => 'gauge',
+                ['labels' => ['freeloader' => false], $this->stats->currentlyWorkingUsers(false)],
+                ['labels' => ['freeloader' => true], $this->stats->currentlyWorkingUsers(true)],
+            ],
+            'work_seconds'         => [
+                'type' => 'gauge',
+                ['labels' => ['state' => 'done'], 'value' => $this->stats->workSeconds(true, false)],
+                ['labels' => ['state' => 'planned'], 'value' => $this->stats->workSeconds(false, false)],
+                ['labels' => ['state' => 'freeloaded'], 'value' => $this->stats->workSeconds(null, true)],
+            ],
+            'registration_enabled' => ['type' => 'gauge', $this->config->get('registration_enabled')],
+        ];
+
+        $data['scrape_duration_seconds'] = [
+            'type' => 'gauge',
+            'help' => 'Duration of the current request',
+            microtime(true) - $this->request->server->get('REQUEST_TIME_FLOAT', $now)
+        ];
+
+        return $this->response
+            ->withHeader('Content-Type', 'text/plain; version=0.0.4')
+            ->withContent($this->engine->get('/metrics', $data));
+    }
+
+    /**
+     * @return Response
+     */
+    public function stats()
+    {
+        $this->checkAuth(true);
+
+        $data = [
+            'user_count'         => $this->stats->newUsers() + $this->stats->arrivedUsers(),
+            'arrived_user_count' => $this->stats->arrivedUsers(),
+            'done_work_hours'    => round($this->stats->workSeconds(true) / 60 / 60, 0),
+            'users_in_action'    => $this->stats->currentlyWorkingUsers(),
+        ];
+
+        return $this->response
+            ->withHeader('Content-Type', 'application/json')
+            ->withContent(json_encode($data));
+    }
+
+    /**
+     * Ensure that the if the request is authorized
+     *
+     * @param bool $isJson
+     */
+    protected function checkAuth($isJson = false)
+    {
+        $apiKey = $this->config->get('api_key');
+        if (empty($apiKey) || $this->request->get('api_key') == $apiKey) {
+            return;
+        }
+
+        $message = 'The api_key is invalid';
+        $headers = [];
+
+        if ($isJson) {
+            $message = json_encode(['error' => $message]);
+            $headers['Content-Type'] = 'application/json';
+        }
+
+        throw new HttpForbidden($message, $headers);
+    }
+}
diff --git a/src/Controllers/Metrics/MetricsEngine.php b/src/Controllers/Metrics/MetricsEngine.php
new file mode 100644
index 00000000..eeb47d8a
--- /dev/null
+++ b/src/Controllers/Metrics/MetricsEngine.php
@@ -0,0 +1,137 @@
+<?php
+
+namespace Engelsystem\Controllers\Metrics;
+
+use Engelsystem\Renderer\EngineInterface;
+
+class MetricsEngine implements EngineInterface
+{
+    /**
+     * Render metrics
+     *
+     * @example $data = ['foo' => [['labels' => ['foo'=>'bar'], 'value'=>42]], 'bar'=>123]
+     *
+     * @param string  $path
+     * @param mixed[] $data
+     * @return string
+     */
+    public function get($path, $data = []): string
+    {
+        $return = [];
+        foreach ($data as $name => $list) {
+            if (is_int($name)) {
+                $return[] = '# ' . $this->escape($list);
+                continue;
+            }
+
+            $list = is_array($list) ? $list : [$list];
+            $name = 'engelsystem_' . $name;
+
+            if (isset($list['help'])) {
+                $return[] = sprintf('# HELP %s %s', $name, $this->escape($list['help']));
+                unset($list['help']);
+            }
+
+            if (isset($list['type'])) {
+                $return[] = sprintf('# TYPE %s %s', $name, $list['type']);
+                unset($list['type']);
+            }
+
+            $list = (!isset($list['value']) || !isset($list['labels'])) ? $list : [$list];
+            foreach ($list as $row) {
+                $row = is_array($row) ? $row : [$row];
+
+                $return[] = $this->formatData($name, $row);
+            }
+        }
+
+        return implode("\n", $return);
+    }
+
+    /**
+     * @param string $path
+     * @return bool
+     */
+    public function canRender($path): bool
+    {
+        return $path == '/metrics';
+    }
+
+    /**
+     * @param string      $name
+     * @param array|mixed $row
+     * @see https://prometheus.io/docs/instrumenting/exposition_formats/
+     * @return string
+     */
+    protected function formatData($name, $row): string
+    {
+        return sprintf(
+            '%s%s %s',
+            $name,
+            $this->renderLabels($row),
+            $this->renderValue($row));
+    }
+
+    /**
+     * @param array|mixed $row
+     * @return mixed
+     */
+    protected function renderLabels($row): string
+    {
+        $labels = [];
+        if (!is_array($row) || empty($row['labels'])) {
+            return '';
+        }
+
+        foreach ($row['labels'] as $type => $value) {
+            $labels[$type] = $type . '="' . $this->formatValue($value) . '"';
+        }
+
+        return '{' . implode(',', $labels) . '}';
+    }
+
+    /**
+     * @param array|mixed $row
+     * @return mixed
+     */
+    protected function renderValue($row)
+    {
+        if (isset($row['value'])) {
+            return $this->formatValue($row['value']);
+        }
+
+        return $this->formatValue(array_pop($row));
+    }
+
+    /**
+     * @param mixed $value
+     * @return mixed
+     */
+    protected function formatValue($value)
+    {
+        if (is_bool($value)) {
+            return (int)$value;
+        }
+
+        return $this->escape($value);
+    }
+
+    /**
+     * @param mixed $value
+     * @return mixed
+     */
+    protected function escape($value)
+    {
+        $replace = [
+            '\\' => '\\\\',
+            '"'  => '\\"',
+            "\n" => '\\n',
+        ];
+
+        return str_replace(
+            array_keys($replace),
+            array_values($replace),
+            $value
+        );
+    }
+}
diff --git a/src/Controllers/Metrics/Stats.php b/src/Controllers/Metrics/Stats.php
new file mode 100644
index 00000000..891f8c80
--- /dev/null
+++ b/src/Controllers/Metrics/Stats.php
@@ -0,0 +1,144 @@
+<?php
+
+namespace Engelsystem\Controllers\Metrics;
+
+use Engelsystem\Database\Database;
+use Illuminate\Database\Query\Builder as QueryBuilder;
+use Illuminate\Database\Query\Expression as QueryExpression;
+
+class Stats
+{
+    /** @var Database */
+    protected $db;
+
+    /**
+     * @param Database $db
+     */
+    public function __construct(Database $db)
+    {
+        $this->db = $db;
+    }
+
+    /**
+     * The number of not arrived users
+     *
+     * @param null $working
+     * @return int
+     */
+    public function arrivedUsers($working = null): int
+    {
+        $query = $this
+            ->getQuery('users')
+            ->join('users_state', 'user_id', '=', 'id')
+            ->where('arrived', '=', 1);
+
+        if (!is_null($working)) {
+            // @codeCoverageIgnoreStart
+            $query
+                ->leftJoin('UserWorkLog', 'UserWorkLog.user_id', '=', 'users.id')
+                ->leftJoin('ShiftEntry', 'ShiftEntry.UID', '=', 'users.id')
+                ->groupBy('users.id');
+
+            $query->where(function ($query) use ($working) {
+                /** @var QueryBuilder $query */
+                if ($working) {
+                    $query
+                        ->whereNotNull('ShiftEntry.SID')
+                        ->orWhereNotNull('UserWorkLog.work_hours');
+
+                    return;
+                }
+                $query
+                    ->whereNull('ShiftEntry.SID')
+                    ->whereNull('UserWorkLog.work_hours');
+            });
+            // @codeCoverageIgnoreEnd
+        }
+
+        return $query
+            ->count();
+    }
+
+    /**
+     * The number of not arrived users
+     *
+     * @return int
+     */
+    public function newUsers(): int
+    {
+        return $this
+            ->getQuery('users')
+            ->join('users_state', 'user_id', '=', 'id')
+            ->where('arrived', '=', 0)
+            ->count();
+    }
+
+    /**
+     * The number of currently working users
+     *
+     * @param null $freeloaded
+     * @return int
+     * @codeCoverageIgnore
+     */
+    public function currentlyWorkingUsers($freeloaded = null): int
+    {
+        $query = $this
+            ->getQuery('users')
+            ->join('ShiftEntry', 'ShiftEntry.UID', '=', 'users.id')
+            ->join('Shifts', 'Shifts.SID', '=', 'ShiftEntry.SID')
+            ->where('Shifts.start', '<=', time())
+            ->where('Shifts.end', '>', time());
+
+        if (!is_null($freeloaded)) {
+            $query->where('ShiftEntry.freeloaded', '=', $freeloaded);
+        }
+
+        return $query->count();
+    }
+
+    /**
+     * The number of worked shifts
+     *
+     * @param bool|null $done
+     * @param bool|null $freeloaded
+     * @return int
+     * @codeCoverageIgnore
+     */
+    public function workSeconds($done = null, $freeloaded = null): int
+    {
+        $query = $this
+            ->getQuery('ShiftEntry')
+            ->join('Shifts', 'Shifts.SID', '=', 'ShiftEntry.SID');
+
+        if (!is_null($freeloaded)) {
+            $query->where('freeloaded', '=', $freeloaded);
+        }
+
+        if (!is_null($done)) {
+            $query->where('end', ($done == true ? '<' : '>='), time());
+        }
+
+        return $query->sum($this->raw('end - start'));
+    }
+
+    /**
+     * @param string $table
+     * @return QueryBuilder
+     */
+    protected function getQuery(string $table): QueryBuilder
+    {
+        return $this->db
+            ->getConnection()
+            ->table($table);
+    }
+
+    /**
+     * @param mixed $value
+     * @return QueryExpression
+     * @codeCoverageIgnore
+     */
+    protected function raw($value)
+    {
+        return $this->db->getConnection()->raw($value);
+    }
+}
diff --git a/src/Middleware/LegacyMiddleware.php b/src/Middleware/LegacyMiddleware.php
index b1315fda..8524764f 100644
--- a/src/Middleware/LegacyMiddleware.php
+++ b/src/Middleware/LegacyMiddleware.php
@@ -26,7 +26,6 @@ class LegacyMiddleware implements MiddlewareInterface
         'shift_entries',
         'shifts',
         'shifts_json_export',
-        'stats',
         'users',
         'user_driver_licenses',
         'user_password_recovery',
@@ -122,10 +121,6 @@ class LegacyMiddleware implements MiddlewareInterface
             case 'shifts_json_export':
                 require_once realpath(__DIR__ . '/../../includes/controller/shifts_controller.php');
                 shifts_json_export_controller();
-            /** @noinspection PhpMissingBreakStatementInspection */
-            case 'stats':
-                require_once realpath(__DIR__ . '/../../includes/pages/guest_stats.php');
-                guest_stats();
             case 'user_password_recovery':
                 require_once realpath(__DIR__ . '/../../includes/controller/users_controller.php');
                 $title = user_password_recovery_title();
diff --git a/tests/Unit/Controllers/Metrics/ControllerTest.php b/tests/Unit/Controllers/Metrics/ControllerTest.php
new file mode 100644
index 00000000..013a3352
--- /dev/null
+++ b/tests/Unit/Controllers/Metrics/ControllerTest.php
@@ -0,0 +1,165 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Controllers\Metrics;
+
+use Engelsystem\Config\Config;
+use Engelsystem\Controllers\Metrics\Controller;
+use Engelsystem\Controllers\Metrics\MetricsEngine;
+use Engelsystem\Controllers\Metrics\Stats;
+use Engelsystem\Http\Exceptions\HttpForbidden;
+use Engelsystem\Http\Request;
+use Engelsystem\Http\Response;
+use Engelsystem\Test\Unit\TestCase;
+use PHPUnit\Framework\MockObject\MockObject;
+use Symfony\Component\HttpFoundation\ServerBag;
+
+class ControllerTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Controller::__construct
+     * @covers \Engelsystem\Controllers\Metrics\Controller::metrics
+     */
+    public function testMetrics()
+    {
+        /** @var Response|MockObject $response */
+        /** @var Request|MockObject $request */
+        /** @var MetricsEngine|MockObject $engine */
+        /** @var Stats|MockObject $stats */
+        /** @var Config $config */
+        list($response, $request, $engine, $stats, $config) = $this->getMocks();
+
+        $request->server = new ServerBag();
+        $request->server->set('REQUEST_TIME_FLOAT', 0.0123456789);
+
+        $engine->expects($this->once())
+            ->method('get')
+            ->willReturnCallback(function ($path, $data) use ($response) {
+                $this->assertEquals('/metrics', $path);
+                $this->assertArrayHasKey('users', $data);
+                $this->assertArrayHasKey('users_working', $data);
+                $this->assertArrayHasKey('work_seconds', $data);
+                $this->assertArrayHasKey('registration_enabled', $data);
+                $this->assertArrayHasKey('scrape_duration_seconds', $data);
+
+                return 'metrics return';
+            });
+
+        $response->expects($this->once())
+            ->method('withHeader')
+            ->with('Content-Type', 'text/plain; version=0.0.4')
+            ->willReturn($response);
+        $response->expects($this->once())
+            ->method('withContent')
+            ->with('metrics return')
+            ->willReturn($response);
+
+        $stats->expects($this->exactly(2))
+            ->method('arrivedUsers')
+            ->withConsecutive([false], [true])
+            ->willReturnOnConsecutiveCalls(7, 43);
+        $stats->expects($this->exactly(2))
+            ->method('currentlyWorkingUsers')
+            ->withConsecutive([false], [true])
+            ->willReturnOnConsecutiveCalls(10, 1);
+        $stats->expects($this->exactly(3))
+            ->method('workSeconds')
+            ->withConsecutive([true, false], [false, false], [null, true])
+            ->willReturnOnConsecutiveCalls(60 * 37, 60 * 251, 60 * 3);
+        $this->setExpects($stats, 'newUsers', null, 9);
+
+        $config->set('registration_enabled', 1);
+
+        $controller = new Controller($response, $engine, $config, $request, $stats);
+        $controller->metrics();
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Controller::stats
+     * @covers \Engelsystem\Controllers\Metrics\Controller::checkAuth
+     */
+    public function testStats()
+    {
+        /** @var Response|MockObject $response */
+        /** @var Request|MockObject $request */
+        /** @var MetricsEngine|MockObject $engine */
+        /** @var Stats|MockObject $stats */
+        /** @var Config $config */
+        list($response, $request, $engine, $stats, $config) = $this->getMocks();
+
+        $response->expects($this->once())
+            ->method('withHeader')
+            ->with('Content-Type', 'application/json')
+            ->willReturn($response);
+        $response->expects($this->once())
+            ->method('withContent')
+            ->with(json_encode([
+                'user_count'         => 13,
+                'arrived_user_count' => 10,
+                'done_work_hours'    => 99,
+                'users_in_action'    => 5
+            ]))
+            ->willReturn($response);
+
+        $request->expects($this->once())
+            ->method('get')
+            ->with('api_key')
+            ->willReturn('ApiKey987');
+
+        $config->set('api_key', 'ApiKey987');
+
+        $stats->expects($this->once())
+            ->method('workSeconds')
+            ->with(true)
+            ->willReturn(60 * 60 * 99.47);
+        $this->setExpects($stats, 'newUsers', null, 3);
+        $this->setExpects($stats, 'arrivedUsers', null, 10, $this->exactly(2));
+        $this->setExpects($stats, 'currentlyWorkingUsers', null, 5);
+
+        $controller = new Controller($response, $engine, $config, $request, $stats);
+        $controller->stats();
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Controller::checkAuth
+     */
+    public function testCheckAuth()
+    {
+        /** @var Response|MockObject $response */
+        /** @var Request|MockObject $request */
+        /** @var MetricsEngine|MockObject $engine */
+        /** @var Stats|MockObject $stats */
+        /** @var Config $config */
+        list($response, $request, $engine, $stats, $config) = $this->getMocks();
+
+        $request->expects($this->once())
+            ->method('get')
+            ->with('api_key')
+            ->willReturn('LoremIpsum!');
+
+        $config->set('api_key', 'fooBar!');
+
+        $controller = new Controller($response, $engine, $config, $request, $stats);
+
+        $this->expectException(HttpForbidden::class);
+        $this->expectExceptionMessage(json_encode(['error' => 'The api_key is invalid']));
+        $controller->stats();
+    }
+
+    /**
+     * @return array
+     */
+    protected function getMocks(): array
+    {
+        /** @var Response|MockObject $response */
+        $response = $this->createMock(Response::class);
+        /** @var Request|MockObject $request */
+        $request = $this->createMock(Request::class);
+        /** @var MetricsEngine|MockObject $engine */
+        $engine = $this->createMock(MetricsEngine::class);
+        /** @var Stats|MockObject $stats */
+        $stats = $this->createMock(Stats::class);
+        $config = new Config();
+
+        return array($response, $request, $engine, $stats, $config);
+    }
+}
diff --git a/tests/Unit/Controllers/Metrics/MetricsEngineTest.php b/tests/Unit/Controllers/Metrics/MetricsEngineTest.php
new file mode 100644
index 00000000..b810b10a
--- /dev/null
+++ b/tests/Unit/Controllers/Metrics/MetricsEngineTest.php
@@ -0,0 +1,69 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Controllers\Metrics;
+
+use Engelsystem\Controllers\Metrics\MetricsEngine;
+use Engelsystem\Test\Unit\TestCase;
+
+class MetricsEngineTest extends TestCase
+{
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::get
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::formatData
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::renderLabels
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::renderValue
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::formatValue
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::escape
+     */
+    public function testGet()
+    {
+        $engine = new MetricsEngine();
+
+        $this->assertEquals('', $engine->get('/metrics'));
+
+        $this->assertEquals('engelsystem_users 13', $engine->get('/metrics', ['users' => 13]));
+
+        $this->assertEquals('engelsystem_bool_val 0', $engine->get('/metrics', ['bool_val' => false]));
+
+        $this->assertEquals('# Lorem \n Ipsum', $engine->get('/metrics', ["Lorem \n Ipsum"]));
+
+        $this->assertEquals(
+            'engelsystem_foo{lorem="ip\\\\sum"} \\"lorem\\n\\\\ipsum\\"',
+            $engine->get('/metrics', [
+                'foo' => ['labels' => ['lorem' => 'ip\\sum'], 'value' => "\"lorem\n\\ipsum\""]
+            ])
+        );
+
+        $this->assertEquals(
+            'engelsystem_foo_count{bar="14"} 42',
+            $engine->get('/metrics', ['foo_count' => ['labels' => ['bar' => 14], 'value' => 42],])
+        );
+
+        $this->assertEquals(
+            'engelsystem_lorem{test="123"} NaN' . "\n" . 'engelsystem_lorem{test="456"} 999.99',
+            $engine->get('/metrics', [
+                'lorem' => [
+                    ['labels' => ['test' => 123], 'value' => 'NaN'],
+                    ['labels' => ['test' => 456], 'value' => 999.99],
+                ],
+            ])
+        );
+
+        $this->assertEquals(
+            "# HELP engelsystem_test Some help\\n  text\n# TYPE engelsystem_test counter\nengelsystem_test 99",
+            $engine->get('/metrics', ['test' => ['help' => "Some help\n  text", 'type' => 'counter', 'value' => 99]])
+        );
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\MetricsEngine::canRender
+     */
+    public function testCanRender()
+    {
+        $engine = new MetricsEngine();
+
+        $this->assertFalse($engine->canRender('/'));
+        $this->assertFalse($engine->canRender('/metrics.foo'));
+        $this->assertTrue($engine->canRender('/metrics'));
+    }
+}
diff --git a/tests/Unit/Controllers/Metrics/StatsTest.php b/tests/Unit/Controllers/Metrics/StatsTest.php
new file mode 100644
index 00000000..1618b99b
--- /dev/null
+++ b/tests/Unit/Controllers/Metrics/StatsTest.php
@@ -0,0 +1,74 @@
+<?php
+
+namespace Engelsystem\Test\Unit\Controllers\Metrics;
+
+use Engelsystem\Controllers\Metrics\Stats;
+use Engelsystem\Models\User\State;
+use Engelsystem\Models\User\User;
+use Engelsystem\Test\Unit\HasDatabase;
+use Engelsystem\Test\Unit\TestCase;
+use Illuminate\Support\Str;
+
+class StatsTest extends TestCase
+{
+    use HasDatabase;
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Stats::newUsers
+     * @covers \Engelsystem\Controllers\Metrics\Stats::getQuery
+     * @covers \Engelsystem\Controllers\Metrics\Stats::__construct
+     */
+    public function testNewUsers()
+    {
+        $this->initDatabase();
+        $this->addUsers();
+
+        $stats = new Stats($this->database);
+        $this->assertEquals(2, $stats->newUsers());
+    }
+
+    /**
+     * @covers \Engelsystem\Controllers\Metrics\Stats::arrivedUsers
+     */
+    public function testArrivedUsers()
+    {
+        $this->initDatabase();
+        $this->addUsers();
+
+        $stats = new Stats($this->database);
+        $this->assertEquals(3, $stats->arrivedUsers());
+    }
+
+    /**
+     * Add some example users
+     */
+    protected function addUsers()
+    {
+        $this->addUser();
+        $this->addUser();
+        $this->addUser(['arrived' => 1]);
+        $this->addUser(['arrived' => 1, 'active' => 1]);
+        $this->addUser(['arrived' => 1, 'active' => 1]);
+    }
+
+    /**
+     * @param array $state
+     */
+    protected function addUser(array $state = [])
+    {
+        $name = 'user_' . Str::random(5);
+
+        $user = new User([
+            'name'     => $name,
+            'password' => '',
+            'email'    => $name . '@engel.example.com',
+            'api_key'  => '',
+        ]);
+        $user->save();
+
+        $state = new State($state);
+        $state->user()
+            ->associate($user)
+            ->save();
+    }
+}