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Testing Tx3g Subtitle Decoder Implementation in SmartTube

This test suite validates the Tx3gDecoder functionality in ExoPlayer, focusing on subtitle decoding capabilities including text styling, character encoding, and positioning. The tests ensure proper handling of various subtitle formats and initialization parameters.

Test Coverage Overview

The test suite provides comprehensive coverage of Tx3gDecoder functionality, examining subtitle decoding across multiple scenarios.

Basic text decoding without styling
Styled text with formatting (bold, italic, underline)
UTF-16 character encoding (both BE and LE)
Multiple style applications
Custom positioning and initialization parameters

Implementation Analysis

The testing approach utilizes JUnit4 with AndroidJUnit4 runner for Android-specific testing requirements. Tests are structured around byte array inputs representing different subtitle formats and configurations, with careful validation of the decoded output including text content, styling spans, and positioning parameters.

Technical Details

Testing tools and configuration:

JUnit4 test framework
AndroidJUnit4 test runner
TestUtil for byte array handling
ApplicationProvider for context access
Various Android text styling classes (SpannedString, StyleSpan, etc.)

Best Practices Demonstrated

The test suite exemplifies strong testing practices through comprehensive edge case coverage, clear test method naming, and thorough assertion checking. Each test focuses on a specific aspect of functionality with proper setup and validation of both content and styling attributes.

yuliskov/smarttube

exoplayer-amzn-2.10.6/library/core/src/test/java/com/google/android/exoplayer2/text/tx3g/Tx3gDecoderTest.java

            
/*
 * Copyright (C) 2016 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.text.tx3g;

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.fail;

import android.graphics.Color;
import android.graphics.Typeface;
import android.text.SpannedString;
import android.text.style.ForegroundColorSpan;
import android.text.style.StyleSpan;
import android.text.style.TypefaceSpan;
import android.text.style.UnderlineSpan;
import androidx.test.core.app.ApplicationProvider;
import androidx.test.ext.junit.runners.AndroidJUnit4;
import com.google.android.exoplayer2.C;
import com.google.android.exoplayer2.testutil.TestUtil;
import com.google.android.exoplayer2.text.Cue;
import com.google.android.exoplayer2.text.Subtitle;
import com.google.android.exoplayer2.text.SubtitleDecoderException;
import java.io.IOException;
import java.util.Collections;
import org.junit.Test;
import org.junit.runner.RunWith;

/** Unit test for {@link Tx3gDecoder}. */
@RunWith(AndroidJUnit4.class)
public final class Tx3gDecoderTest {

  private static final String NO_SUBTITLE = "tx3g/no_subtitle";
  private static final String SAMPLE_JUST_TEXT = "tx3g/sample_just_text";
  private static final String SAMPLE_WITH_STYL = "tx3g/sample_with_styl";
  private static final String SAMPLE_WITH_STYL_ALL_DEFAULTS = "tx3g/sample_with_styl_all_defaults";
  private static final String SAMPLE_UTF16_BE_NO_STYL = "tx3g/sample_utf16_be_no_styl";
  private static final String SAMPLE_UTF16_LE_NO_STYL = "tx3g/sample_utf16_le_no_styl";
  private static final String SAMPLE_WITH_MULTIPLE_STYL = "tx3g/sample_with_multiple_styl";
  private static final String SAMPLE_WITH_OTHER_EXTENSION = "tx3g/sample_with_other_extension";
  private static final String SAMPLE_WITH_TBOX = "tx3g/sample_with_tbox";
  private static final String INITIALIZATION = "tx3g/initialization";
  private static final String INITIALIZATION_ALL_DEFAULTS = "tx3g/initialization_all_defaults";

  @Test
  public void testDecodeNoSubtitle() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes = TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), NO_SUBTITLE);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    assertThat(subtitle.getCues(0)).isEmpty();
  }

  @Test
  public void testDecodeJustText() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_JUST_TEXT);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(0);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testDecodeWithStyl() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_WITH_STYL);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(3);
    StyleSpan styleSpan = findSpan(text, 0, 6, StyleSpan.class);
    assertThat(styleSpan.getStyle()).isEqualTo(Typeface.BOLD_ITALIC);
    findSpan(text, 0, 6, UnderlineSpan.class);
    ForegroundColorSpan colorSpan = findSpan(text, 0, 6, ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.GREEN);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testDecodeWithStylAllDefaults() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), SAMPLE_WITH_STYL_ALL_DEFAULTS);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(0);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testDecodeUtf16BeNoStyl() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_UTF16_BE_NO_STYL);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("你好");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(0);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testDecodeUtf16LeNoStyl() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_UTF16_LE_NO_STYL);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("你好");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(0);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testDecodeWithMultipleStyl() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), SAMPLE_WITH_MULTIPLE_STYL);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("Line 2\nLine 3");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(4);
    StyleSpan styleSpan = findSpan(text, 0, 5, StyleSpan.class);
    assertThat(styleSpan.getStyle()).isEqualTo(Typeface.ITALIC);
    findSpan(text, 7, 12, UnderlineSpan.class);
    ForegroundColorSpan colorSpan = findSpan(text, 0, 5, ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.GREEN);
    colorSpan = findSpan(text, 7, 12, ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.GREEN);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testDecodeWithOtherExtension() throws IOException, SubtitleDecoderException {
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.emptyList());
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), SAMPLE_WITH_OTHER_EXTENSION);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(2);
    StyleSpan styleSpan = findSpan(text, 0, 6, StyleSpan.class);
    assertThat(styleSpan.getStyle()).isEqualTo(Typeface.BOLD);
    ForegroundColorSpan colorSpan = findSpan(text, 0, 6, ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.GREEN);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  @Test
  public void testInitializationDecodeWithStyl() throws IOException, SubtitleDecoderException {
    byte[] initBytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), INITIALIZATION);
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.singletonList(initBytes));
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_WITH_STYL);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(5);
    StyleSpan styleSpan = findSpan(text, 0, text.length(), StyleSpan.class);
    assertThat(styleSpan.getStyle()).isEqualTo(Typeface.BOLD_ITALIC);
    findSpan(text, 0, text.length(), UnderlineSpan.class);
    TypefaceSpan typefaceSpan = findSpan(text, 0, text.length(), TypefaceSpan.class);
    assertThat(typefaceSpan.getFamily()).isEqualTo(C.SERIF_NAME);
    ForegroundColorSpan colorSpan = findSpan(text, 0, text.length(), ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.RED);
    colorSpan = findSpan(text, 0, 6, ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.GREEN);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.1f);
  }

  @Test
  public void testInitializationDecodeWithTbox() throws IOException, SubtitleDecoderException {
    byte[] initBytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), INITIALIZATION);
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.singletonList(initBytes));
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_WITH_TBOX);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(4);
    StyleSpan styleSpan = findSpan(text, 0, text.length(), StyleSpan.class);
    assertThat(styleSpan.getStyle()).isEqualTo(Typeface.BOLD_ITALIC);
    findSpan(text, 0, text.length(), UnderlineSpan.class);
    TypefaceSpan typefaceSpan = findSpan(text, 0, text.length(), TypefaceSpan.class);
    assertThat(typefaceSpan.getFamily()).isEqualTo(C.SERIF_NAME);
    ForegroundColorSpan colorSpan = findSpan(text, 0, text.length(), ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.RED);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.1875f);
  }

  @Test
  public void testInitializationAllDefaultsDecodeWithStyl()
      throws IOException, SubtitleDecoderException {
    byte[] initBytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), INITIALIZATION_ALL_DEFAULTS);
    Tx3gDecoder decoder = new Tx3gDecoder(Collections.singletonList(initBytes));
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), SAMPLE_WITH_STYL);
    Subtitle subtitle = decoder.decode(bytes, bytes.length, false);
    SpannedString text = new SpannedString(subtitle.getCues(0).get(0).text);
    assertThat(text.toString()).isEqualTo("CC Test");
    assertThat(text.getSpans(0, text.length(), Object.class)).hasLength(3);
    StyleSpan styleSpan = findSpan(text, 0, 6, StyleSpan.class);
    assertThat(styleSpan.getStyle()).isEqualTo(Typeface.BOLD_ITALIC);
    findSpan(text, 0, 6, UnderlineSpan.class);
    ForegroundColorSpan colorSpan = findSpan(text, 0, 6, ForegroundColorSpan.class);
    assertThat(colorSpan.getForegroundColor()).isEqualTo(Color.GREEN);
    assertFractionalLinePosition(subtitle.getCues(0).get(0), 0.85f);
  }

  private static <T> T findSpan(
      SpannedString testObject, int expectedStart, int expectedEnd, Class<T> expectedType) {
    T[] spans = testObject.getSpans(0, testObject.length(), expectedType);
    for (T span : spans) {
      if (testObject.getSpanStart(span) == expectedStart
          && testObject.getSpanEnd(span) == expectedEnd) {
        return span;
      }
    }
    fail("Span not found.");
    return null;
  }

  private static void assertFractionalLinePosition(Cue cue, float expectedFraction) {
    assertThat(cue.lineType).isEqualTo(Cue.LINE_TYPE_FRACTION);
    assertThat(cue.lineAnchor).isEqualTo(Cue.ANCHOR_TYPE_START);
    assertThat(Math.abs(expectedFraction - cue.line) < 1e-6).isTrue();
  }
}