add unit tests

tests/MetricsControllerTest.php

@@ -0,0 +1,48 @@
+<?php
+
+namespace Tests;
+
+use Illuminate\Contracts\Routing\ResponseFactory;
+use Illuminate\Http\Response;
+use Mockery;
+use PHPUnit\Framework\TestCase;
+use Prometheus\RenderTextFormat;
+use Superbalist\LaravelPrometheusExporter\MetricsController;
+use Superbalist\LaravelPrometheusExporter\PrometheusExporter;
+
+class MetricsControllerTest extends TestCase
+{
+    public function testConstruct()
+    {
+        $responseFactory = Mockery::mock(ResponseFactory::class);
+        $exporter = Mockery::mock(PrometheusExporter::class);
+        $controller = new MetricsController($responseFactory, $exporter);
+        $this->assertSame($responseFactory, $controller->getResponseFactory());
+        $this->assertSame($exporter, $controller->getPrometheusExporter());
+    }
+
+    public function testGetMetrics()
+    {
+        $response = Mockery::mock(Response::class);
+
+        $responseFactory = Mockery::mock(ResponseFactory::class);
+        $responseFactory->shouldReceive('make')
+            ->once()
+            ->withArgs([
+                "\n",
+                200,
+                ['Content-Type' => RenderTextFormat::MIME_TYPE]
+            ])
+            ->andReturn($response);
+
+        $exporter = Mockery::mock(PrometheusExporter::class);
+        $exporter->shouldReceive('export')
+            ->once()
+            ->andReturn([]);
+
+        $controller = new MetricsController($responseFactory, $exporter);
+
+        $r = $controller->getMetrics();
+        $this->assertSame($response, $r);
+    }
+}