Add Test for Renderer

It was previously untested, it's now covered with unit tests.

Signed-off-by: Rafael Dohms <rdohms@gmail.com>

Author: rdohms

tests/Test/Prometheus/RenderTextFormatTest.php

@@ -0,0 +1,65 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Test\Prometheus;
+
+use Prometheus\CollectorRegistry;
+use Prometheus\Exception\MetricsRegistrationException;
+use Prometheus\MetricFamilySamples;
+use Prometheus\RenderTextFormat;
+use PHPUnit\Framework\TestCase;
+use Prometheus\Storage\InMemory;
+
+class RenderTextFormatTest extends TestCase
+{
+
+    public function testOutputMatchesExpectations(): void
+    {
+        $metrics = $this->buildSamples();
+
+        $renderer = new RenderTextFormat();
+        $output = $renderer->render($metrics);
+
+        self::assertSame($this->getExpectedOutput(), $output);
+    }
+
+    /**
+     * @return MetricFamilySamples[]
+     * @throws MetricsRegistrationException
+     */
+    private function buildSamples(): array
+    {
+        $namespace = 'mynamespace';
+        $registry = new CollectorRegistry(new InMemory(), false);
+        $registry->getOrRegisterCounter($namespace, 'counter', 'counter-help-text', ['label1', 'label2'])
+                 ->inc(['bob', 'al\ice']);
+        $registry->getOrRegisterGauge($namespace, 'gauge', 'counter-help-text', ['label1', 'label2'])
+                 ->inc(["bo\nb", 'ali\"ce']);
+        $registry->getOrRegisterHistogram($namespace, 'histogram', 'counter-help-text', ['label1', 'label2'], [0, 10, 100])
+                 ->observe(5, ['bob', 'alice']);
+
+        return $registry->getMetricFamilySamples();
+    }
+
+    private function getExpectedOutput(): string
+    {
+        return <<<TEXTPLAIN
+# HELP mynamespace_counter counter-help-text
+# TYPE mynamespace_counter counter
+mynamespace_counter{label1="bob",label2="al\\\\ice"} 1
+# HELP mynamespace_gauge counter-help-text
+# TYPE mynamespace_gauge gauge
+mynamespace_gauge{label1="bo\\nb",label2="ali\\\\\"ce"} 1
+# HELP mynamespace_histogram counter-help-text
+# TYPE mynamespace_histogram histogram
+mynamespace_histogram_bucket{label1="bob",label2="alice",le="0"} 0
+mynamespace_histogram_bucket{label1="bob",label2="alice",le="10"} 1
+mynamespace_histogram_bucket{label1="bob",label2="alice",le="100"} 1
+mynamespace_histogram_bucket{label1="bob",label2="alice",le="+Inf"} 1
+mynamespace_histogram_count{label1="bob",label2="alice"} 1
+mynamespace_histogram_sum{label1="bob",label2="alice"} 5
+
+TEXTPLAIN;
+    }
+}