Added som local function tests

lib/src/unofficial_jisho_api_base.dart

@@ -197,7 +197,7 @@ String getGifUri(String kanji) {
 
 int getNewspaperFrequencyRank(String pageHtml) {
   final frequencySection = getStringBetweenStrings(pageHtml, '<div class="frequency">', '</div>');
-  return frequencySection ?? int.parse(getStringBetweenStrings(frequencySection, '<strong>', '</strong>'));
+  return frequencySection.isNotEmpty ? int.parse(getStringBetweenStrings(frequencySection, '<strong>', '</strong>')) : null;
 }
 
 KanjiResult parseKanjiPageData(String pageHtml, String kanji) {

test/local_function_test_cases.dart

@@ -91,23 +91,28 @@ void test_local_functions() async {
   });
 
   test('getRadical', () {
-
+    final result = getRadical(kanjiPage);
+    expect(result, ['ジ']); //FIX
   });
 
   test('getParts', () {
-
+    final result = getParts(kanjiPage);
+    expect(result, ['土', '寸', '日']);
   });
 
   test('getSvgUri', () {
-
+    final result = getSvgUri(kanjiPage);
+    expect(result, 'http://d1w6u4xc3l95km.cloudfront.net/kanji-2015-03/06642.svg');
   });
 
   test('getGifUri', () {
-
+    final result = getGifUri(kanjiPage);
+    expect(result, 'https://raw.githubusercontent.com/mistval/kanji_images/master/gifs/3c.gif');
   });
 
   test('getNewspaperFrequencyRank', () {
-
+    final result = getNewspaperFrequencyRank(kanjiPage);
+    expect(result, 16); //This might change
   });
 
   test('parseKanjiPageData', () {