Incorporated VuFindHttp module test suite; added missing method required by tests.

module/VuFind/tests/phpunit.xml

 <phpunit bootstrap="./bootstrap.php" backupGlobals="false">
   <testsuites>
+    <testsuite name="VuFindHttp">
+      <directory>../../VuFindHttp/tests/unit-tests/src</directory>
+    </testsuite>
     <testsuite name="VuFindUnit">
       <directory>unit-tests/src</directory>
     </testsuite>

module/VuFindHttp/src/VuFindHttp/HttpService.php

@@ -57,6 +57,13 @@ class HttpService implements HttpServiceInterface
      */
     protected $proxyConfig;
 
+    /**
+     * Default adapter
+     *
+     * @var \Zend\Http\Client\Adapter\AdapterInterface
+     */
+    protected $defaultAdapter = null;
+
     /**
      * Constructor.
      *
@@ -149,6 +156,18 @@ class HttpService implements HttpServiceInterface
         return $this->post($url, $body, \Zend\Http\Client::ENC_URLENCODED, $timeout);
     }
 
+    /**
+     * Set a default HTTP adapter (primarily for testing purposes).
+     *
+     * @param \Zend\Http\Client\Adapter\AdapterInterface $adapter Adapter
+     *
+     * @return void
+     */
+    public function setDefaultAdapter(\Zend\Http\Client\Adapter\AdapterInterface $adapter)
+    {
+        $this->defaultAdapter = $adapter;
+    }
+
     /**
      * Return a new HTTP client.
      *
@@ -162,6 +181,9 @@ class HttpService implements HttpServiceInterface
     {
         $client = new \Zend\Http\Client();
         $client->setMethod($method);
+        if (null !== $this->defaultAdapter) {
+            $client->setAdapter($this->defaultAdapter);
+        }
         if (null !== $url) {
             $client->setUri($url);
         }