rewrite unit tests (for wordcamp)

tests/mock_ext_dataservice.php

@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * Mock for FF_Meta_Externaldata
+ * in order to run all unit tests offline with predefined content
+ */
+class MockDataService {
+    function get($url) {
+        // translate file "http://example.org/%s.json" to "./example_%s.json"
+        $url_filename   = basename(parse_url($url, PHP_URL_PATH));
+        $local_filename = __DIR__.'/example_'.$url_filename;
+        if (file_exists($local_filename)) {
+            $json     = file_get_contents($local_filename);
+            $stubdata = json_decode($json, $assoc = true);
+            //error_log("MockDataService: fetch $url from $local_filename", 4);
+            return $stubdata;
+        } else {
+            //error_log("MockDataService: cannot fetch $url", 4);
+            return array();
+        }
+    }
+}