add tests structure

Tests/ClientTest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace D3\LinkmobilityClient\Tests;
+
+use D3\LinkmobilityClient\Client;
+
+class ApiClientTest extends ApiTestCase
+{
+    public string $fixtureApiKey = 'fixtureApiKey';
+    /** @var ApiClient */
+    public Client $api;
+    public string $jsonFixture = 'json_content';
+
+    public function setUp():void
+    {
+        parent::setUp();
+
+        $this->api = new Client($this->fixtureApiKey);
+    }
+    
+    /**
+     * @test
+     */
+    public function testRun()
+    {
+        $this->assertTrue(true);
+    }
+}