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Testing WebVTT Header Detection and BOM Processing in SmartTube

This test suite validates the WebVTT subtitle format handling in ExoPlayer’s HLS module, focusing on header sniffing and byte order mark processing. The tests ensure proper parsing of WebVTT content in various scenarios including different header formats and encoding markers.

Test Coverage Overview

The test coverage focuses on WebvttExtractor’s sniffing capabilities for WebVTT content validation. Key test cases include:

WebVTT header detection with trailing spaces
Byte Order Mark (BOM) processing
Invalid BOM handling
Incomplete header validation
Incorrect header format detection

Implementation Analysis

The testing approach employs JUnit with AndroidJUnit4 runner for Android compatibility. Tests utilize FakeExtractorInput for controlled data injection and TimestampAdjuster for timing synchronization. Each test case focuses on specific byte-level validation scenarios using precise byte array inputs.

Technical Details

Testing tools and configuration:

JUnit test framework with AndroidJUnit4 runner
FakeExtractorInput for simulated data streams
Truth assertion library for test validations
WebvttExtractor implementation with TimestampAdjuster
Byte-level input testing with precise hex values

Best Practices Demonstrated

The test suite demonstrates excellent testing practices including:

Isolated test cases for specific functionality
Comprehensive edge case coverage
Clear test method naming conventions
Efficient test data setup
Proper exception handling and validation

yuliskov/smarttube

exoplayer-amzn-2.10.6/library/hls/src/test/java/com/google/android/exoplayer2/source/hls/WebvttExtractorTest.java

            
/*
 * Copyright (C) 2018 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.android.exoplayer2.source.hls;

import static com.google.common.truth.Truth.assertThat;

import androidx.test.ext.junit.runners.AndroidJUnit4;
import com.google.android.exoplayer2.extractor.ExtractorInput;
import com.google.android.exoplayer2.testutil.FakeExtractorInput;
import com.google.android.exoplayer2.util.TimestampAdjuster;
import java.io.EOFException;
import java.io.IOException;
import org.junit.Test;
import org.junit.runner.RunWith;

/** Tests for {@link WebvttExtractor}. */
@RunWith(AndroidJUnit4.class)
public class WebvttExtractorTest {

  @Test
  public void sniff_sniffsWebvttHeaderWithTrailingSpace() throws IOException, InterruptedException {
    byte[] data = new byte[] {'W', 'E', 'B', 'V', 'T', 'T', ' ', '\t'};
    assertThat(sniffData(data)).isTrue();
  }

  @Test
  public void sniff_discardsByteOrderMark() throws IOException, InterruptedException {
    byte[] data =
        new byte[] {(byte) 0xEF, (byte) 0xBB, (byte) 0xBF, 'W', 'E', 'B', 'V', 'T', 'T', '\n', ' '};
    assertThat(sniffData(data)).isTrue();
  }

  @Test
  public void sniff_failsForIncorrectBom() throws IOException, InterruptedException {
    byte[] data =
        new byte[] {(byte) 0xEF, (byte) 0xBB, (byte) 0xBB, 'W', 'E', 'B', 'V', 'T', 'T', '\n'};
    assertThat(sniffData(data)).isFalse();
  }

  @Test
  public void sniff_failsForIncompleteHeader() throws IOException, InterruptedException {
    byte[] data = new byte[] {'W', 'E', 'B', 'V', 'T', '\n'};
    assertThat(sniffData(data)).isFalse();
  }

  @Test
  public void sniff_failsForIncorrectHeader() throws IOException, InterruptedException {
    byte[] data =
        new byte[] {(byte) 0xEF, (byte) 0xBB, (byte) 0xBF, 'W', 'e', 'B', 'V', 'T', 'T', '\n'};
    assertThat(sniffData(data)).isFalse();
  }

  private static boolean sniffData(byte[] data) throws IOException, InterruptedException {
    ExtractorInput input = new FakeExtractorInput.Builder().setData(data).build();
    try {
      return new WebvttExtractor(/* language= */ null, new TimestampAdjuster(0)).sniff(input);
    } catch (EOFException e) {
      return false;
    }
  }
}