Merge pull request #519 from XiangRongLin/better_logging_error_handling

Better logging, error handling, doc for mock tests

.github/workflows/ci.yml

@@ -32,7 +32,9 @@ jobs:
       - name: Build and run Tests
         run: |
           if [[ $GITHUB_EVENT_NAME == 'schedule' ]]; then
+            echo running with real downloader
             ./gradlew check --stacktrace -Ddownloader=REAL
           else
+            echo running with mock downloader
             ./gradlew check --stacktrace -Ddownloader=MOCK
           fi

extractor/src/test/java/org/schabi/newpipe/downloader/MockDownloader.java

@@ -27,8 +27,9 @@ class MockDownloader extends Downloader {
     public MockDownloader(@Nonnull String path) throws IOException {
         this.path = path;
         this.mocks = new HashMap<>();
-        File folder = new File(path);
-        for (File file : folder.listFiles()) {
+        final File[] files = new File(path).listFiles();
+        if (files != null) {
+            for (File file : files) {
                 if (file.getName().startsWith(RecordingDownloader.FILE_NAME_PREFIX)) {
                     final FileReader reader = new FileReader(file);
                     final TestRequestResponse response = new GsonBuilder()
@@ -39,6 +40,7 @@ class MockDownloader extends Downloader {
                 }
             }
         }
+    }
 
     @Override
     public Response execute(@Nonnull Request request) {

extractor/src/test/java/org/schabi/newpipe/downloader/RecordingDownloader.java

@@ -27,6 +27,10 @@ import javax.annotation.Nonnull;
  * The files <b>must</b> be created on the local dev environment
  * and recreated when the requests made by a test class change.
  * </p>
+ * <p>
+ * Run the test class as a whole and not each test separately.
+ * Make sure the requests made by a class are unique.
+ * </p>
  */
 class RecordingDownloader extends Downloader {