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Testing SubRip Subtitle Decoder Implementation in SmartTube

This test suite validates the SubripDecoder functionality in ExoPlayer, focusing on parsing and decoding SubRip subtitle files with various formats and edge cases. The tests ensure proper handling of subtitle timing, formatting, and text alignment features.

Test Coverage Overview

The test suite provides comprehensive coverage of SubRip subtitle parsing scenarios including:

Empty subtitle files
Typical subtitle formats with multiple cues
Files with byte order marks
Negative timestamps
Missing timecodes and sequences
Subtitle text alignment and positioning tags

Implementation Analysis

The testing approach uses JUnit with AndroidJUnit4 runner for Android compatibility. Tests are structured to verify subtitle parsing accuracy, timing calculations, and text formatting preservation. Each test case isolates specific subtitle file variations to ensure robust decoder functionality.

Technical Details

Key technical components include:

AndroidJUnit4 test runner
TestUtil for byte array handling
ApplicationProvider for context access
Truth assertion library for validation
SubripDecoder implementation testing

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases for specific functionality
Comprehensive edge case coverage
Helper methods for common assertions
Clear test method naming
Structured test data organization

yuliskov/smarttube

exoplayer-amzn-2.10.6/library/core/src/test/java/com/google/android/exoplayer2/text/subrip/SubripDecoderTest.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.subrip;

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

import androidx.test.core.app.ApplicationProvider;
import androidx.test.ext.junit.runners.AndroidJUnit4;
import com.google.android.exoplayer2.testutil.TestUtil;
import com.google.android.exoplayer2.text.Cue;
import java.io.IOException;
import org.junit.Test;
import org.junit.runner.RunWith;

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

  private static final String EMPTY_FILE = "subrip/empty";
  private static final String TYPICAL_FILE = "subrip/typical";
  private static final String TYPICAL_WITH_BYTE_ORDER_MARK = "subrip/typical_with_byte_order_mark";
  private static final String TYPICAL_EXTRA_BLANK_LINE = "subrip/typical_extra_blank_line";
  private static final String TYPICAL_MISSING_TIMECODE = "subrip/typical_missing_timecode";
  private static final String TYPICAL_MISSING_SEQUENCE = "subrip/typical_missing_sequence";
  private static final String TYPICAL_NEGATIVE_TIMESTAMPS = "subrip/typical_negative_timestamps";
  private static final String TYPICAL_UNEXPECTED_END = "subrip/typical_unexpected_end";
  private static final String TYPICAL_WITH_TAGS = "subrip/typical_with_tags";
  private static final String NO_END_TIMECODES_FILE = "subrip/no_end_timecodes";

  @Test
  public void testDecodeEmpty() throws IOException {
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes = TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), EMPTY_FILE);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(0);
    assertThat(subtitle.getCues(0).isEmpty()).isTrue();
  }

  @Test
  public void testDecodeTypical() throws IOException {
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes = TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), TYPICAL_FILE);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(6);
    assertTypicalCue1(subtitle, 0);
    assertTypicalCue2(subtitle, 2);
    assertTypicalCue3(subtitle, 4);
  }

  @Test
  public void testDecodeTypicalWithByteOrderMark() throws IOException {
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), TYPICAL_WITH_BYTE_ORDER_MARK);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(6);
    assertTypicalCue1(subtitle, 0);
    assertTypicalCue2(subtitle, 2);
    assertTypicalCue3(subtitle, 4);
  }

  @Test
  public void testDecodeTypicalExtraBlankLine() throws IOException {
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), TYPICAL_EXTRA_BLANK_LINE);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(6);
    assertTypicalCue1(subtitle, 0);
    assertTypicalCue2(subtitle, 2);
    assertTypicalCue3(subtitle, 4);
  }

  @Test
  public void testDecodeTypicalMissingTimecode() throws IOException {
    // Parsing should succeed, parsing the first and third cues only.
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), TYPICAL_MISSING_TIMECODE);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(4);
    assertTypicalCue1(subtitle, 0);
    assertTypicalCue3(subtitle, 2);
  }

  @Test
  public void testDecodeTypicalMissingSequence() throws IOException {
    // Parsing should succeed, parsing the first and third cues only.
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), TYPICAL_MISSING_SEQUENCE);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(4);
    assertTypicalCue1(subtitle, 0);
    assertTypicalCue3(subtitle, 2);
  }

  @Test
  public void testDecodeTypicalNegativeTimestamps() throws IOException {
    // Parsing should succeed, parsing the third cue only.
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(
            ApplicationProvider.getApplicationContext(), TYPICAL_NEGATIVE_TIMESTAMPS);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(2);
    assertTypicalCue3(subtitle, 0);
  }

  @Test
  public void testDecodeTypicalUnexpectedEnd() throws IOException {
    // Parsing should succeed, parsing the first and second cues only.
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), TYPICAL_UNEXPECTED_END);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(4);
    assertTypicalCue1(subtitle, 0);
    assertTypicalCue2(subtitle, 2);
  }

  @Test
  public void testDecodeNoEndTimecodes() throws IOException {
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), NO_END_TIMECODES_FILE);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertThat(subtitle.getEventTimeCount()).isEqualTo(3);

    assertThat(subtitle.getEventTime(0)).isEqualTo(0);
    assertThat(subtitle.getCues(subtitle.getEventTime(0)).get(0).text.toString())
        .isEqualTo("SubRip doesn't technically allow missing end timecodes.");

    assertThat(subtitle.getEventTime(1)).isEqualTo(2345000);
    assertThat(subtitle.getCues(subtitle.getEventTime(1)).get(0).text.toString())
        .isEqualTo("We interpret it to mean that a subtitle extends to the start of the next one.");

    assertThat(subtitle.getEventTime(2)).isEqualTo(3456000);
    assertThat(subtitle.getCues(subtitle.getEventTime(2)).get(0).text.toString())
        .isEqualTo("Or to the end of the media.");
  }

  @Test
  public void testDecodeCueWithTag() throws IOException {
    SubripDecoder decoder = new SubripDecoder();
    byte[] bytes =
        TestUtil.getByteArray(ApplicationProvider.getApplicationContext(), TYPICAL_WITH_TAGS);
    SubripSubtitle subtitle = decoder.decode(bytes, bytes.length, false);

    assertTypicalCue1(subtitle, 0);
    assertTypicalCue2(subtitle, 2);
    assertTypicalCue3(subtitle, 4);

    assertThat(subtitle.getCues(subtitle.getEventTime(6)).get(0).text.toString())
        .isEqualTo("This { \\an2} is not a valid tag due to the space after the opening bracket.");

    assertThat(subtitle.getCues(subtitle.getEventTime(8)).get(0).text.toString())
        .isEqualTo("This is the fifth subtitle with multiple valid tags.");

    assertAlignmentCue(subtitle, 10, Cue.ANCHOR_TYPE_END, Cue.ANCHOR_TYPE_START); // {/an1}
    assertAlignmentCue(subtitle, 12, Cue.ANCHOR_TYPE_END, Cue.ANCHOR_TYPE_MIDDLE); // {/an2}
    assertAlignmentCue(subtitle, 14, Cue.ANCHOR_TYPE_END, Cue.ANCHOR_TYPE_END); // {/an3}
    assertAlignmentCue(subtitle, 16, Cue.ANCHOR_TYPE_MIDDLE, Cue.ANCHOR_TYPE_START); // {/an4}
    assertAlignmentCue(subtitle, 18, Cue.ANCHOR_TYPE_MIDDLE, Cue.ANCHOR_TYPE_MIDDLE); // {/an5}
    assertAlignmentCue(subtitle, 20, Cue.ANCHOR_TYPE_MIDDLE, Cue.ANCHOR_TYPE_END); // {/an6}
    assertAlignmentCue(subtitle, 22, Cue.ANCHOR_TYPE_START, Cue.ANCHOR_TYPE_START); // {/an7}
    assertAlignmentCue(subtitle, 24, Cue.ANCHOR_TYPE_START, Cue.ANCHOR_TYPE_MIDDLE); // {/an8}
    assertAlignmentCue(subtitle, 26, Cue.ANCHOR_TYPE_START, Cue.ANCHOR_TYPE_END); // {/an9}
  }

  private static void assertTypicalCue1(SubripSubtitle subtitle, int eventIndex) {
    assertThat(subtitle.getEventTime(eventIndex)).isEqualTo(0);
    assertThat(subtitle.getCues(subtitle.getEventTime(eventIndex)).get(0).text.toString())
        .isEqualTo("This is the first subtitle.");
    assertThat(subtitle.getEventTime(eventIndex + 1)).isEqualTo(1234000);
  }

  private static void assertTypicalCue2(SubripSubtitle subtitle, int eventIndex) {
    assertThat(subtitle.getEventTime(eventIndex)).isEqualTo(2345000);
    assertThat(subtitle.getCues(subtitle.getEventTime(eventIndex)).get(0).text.toString())
        .isEqualTo("This is the second subtitle.\nSecond subtitle with second line.");
    assertThat(subtitle.getEventTime(eventIndex + 1)).isEqualTo(3456000);
  }

  private static void assertTypicalCue3(SubripSubtitle subtitle, int eventIndex) {
    assertThat(subtitle.getEventTime(eventIndex)).isEqualTo(4567000);
    assertThat(subtitle.getCues(subtitle.getEventTime(eventIndex)).get(0).text.toString())
        .isEqualTo("This is the third subtitle.");
    assertThat(subtitle.getEventTime(eventIndex + 1)).isEqualTo(8901000);
  }

  private static void assertAlignmentCue(
      SubripSubtitle subtitle,
      int eventIndex,
      @Cue.AnchorType int lineAnchor,
      @Cue.AnchorType int positionAnchor) {
    long eventTimeUs = subtitle.getEventTime(eventIndex);
    Cue cue = subtitle.getCues(eventTimeUs).get(0);
    assertThat(cue.lineType).isEqualTo(Cue.LINE_TYPE_FRACTION);
    assertThat(cue.lineAnchor).isEqualTo(lineAnchor);
    assertThat(cue.line).isEqualTo(SubripDecoder.getFractionalPositionForAnchorType(lineAnchor));
    assertThat(cue.positionAnchor).isEqualTo(positionAnchor);
    assertThat(cue.position)
        .isEqualTo(SubripDecoder.getFractionalPositionForAnchorType(positionAnchor));
  }
}