Add tests for 0 results METAR

tests/MetarTest.php

@@ -247,4 +247,15 @@ class MetarTest extends TestCase
         $metar = $airportSvc->getMetar('7AK4');
         $this->assertNull($metar);
     }
+
+    public function testHttpCallNoResults()
+    {
+        $this->mockXmlResponse('aviationweather/no_results.xml');
+
+        /** @var AirportService $airportSvc */
+        $airportSvc = app(AirportService::class);
+
+        $metar = $airportSvc->getMetar('AYMR');
+        $this->assertNull($metar);
+    }
 }

tests/data/aviationweather/no_results.xml

@@ -0,0 +1,9 @@
+<response xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.2" xsi:noNamespaceSchemaLocation="http://www.aviationweather.gov/static/adds/schema/metar1_2.xsd">
+<request_index>414399629</request_index>
+<data_source name="metars"/>
+<request type="retrieve"/>
+<errors/>
+<warnings/>
+<time_taken_ms>5</time_taken_ms>
+<data num_results="0"/>
+</response>