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Testing Variable-Length Integer Parsing Implementation in SmartTube

This test suite validates the VarintReader implementation in ExoPlayer’s MKV extractor component, focusing on variable-length integer parsing functionality. The tests verify correct handling of different varint lengths, edge cases, and error conditions in the context of media file parsing.

Test Coverage Overview

The test suite provides comprehensive coverage of varint reading operations across multiple scenarios.

Tests variable-length integers from 1 to 8 bytes
Validates zero values, 64-bit values, and maximum values for each length
Covers end-of-input conditions and maximum length exceeded scenarios
Tests both masked and unmasked value reading

Implementation Analysis

The testing approach employs systematic validation of the VarintReader class using JUnit and AndroidJUnit4 runner. The implementation uses the FakeExtractorInput class to simulate various input conditions and error scenarios, allowing thorough testing of the varint parsing logic.

Key patterns include parameterized test data arrays and dedicated test methods for both normal and flaky input conditions.

Technical Details

Testing Framework: JUnit with AndroidJUnit4 runner
Mock Objects: FakeExtractorInput for simulating input streams
Test Data: Predefined byte arrays for different varint lengths
Error Simulation: SimulatedIOException for testing error handling
Validation: Truth assertion library for result verification

Best Practices Demonstrated

The test suite exemplifies several testing best practices in media processing implementations.

Comprehensive edge case coverage
Systematic test data organization
Robust error condition handling
Clear test method naming and organization
Effective use of mock objects and simulation

yuliskov/smarttube

exoplayer-amzn-2.10.6/library/core/src/test/java/com/google/android/exoplayer2/extractor/mkv/VarintReaderTest.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.extractor.mkv;

import static com.google.android.exoplayer2.C.RESULT_END_OF_INPUT;
import static com.google.android.exoplayer2.C.RESULT_MAX_LENGTH_EXCEEDED;
import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.fail;

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

/** Tests for {@link VarintReader}. */
@RunWith(AndroidJUnit4.class)
public final class VarintReaderTest {

  private static final byte MAX_BYTE = (byte) 0xFF;

  private static final byte[] DATA_1_BYTE_0 = new byte[] {(byte) 0x80};
  private static final byte[] DATA_2_BYTE_0 = new byte[] {0x40, 0};
  private static final byte[] DATA_3_BYTE_0 = new byte[] {0x20, 0, 0};
  private static final byte[] DATA_4_BYTE_0 = new byte[] {0x10, 0, 0, 0};
  private static final byte[] DATA_5_BYTE_0 = new byte[] {0x08, 0, 0, 0, 0};
  private static final byte[] DATA_6_BYTE_0 = new byte[] {0x04, 0, 0, 0, 0, 0};
  private static final byte[] DATA_7_BYTE_0 = new byte[] {0x02, 0, 0, 0, 0, 0, 0};
  private static final byte[] DATA_8_BYTE_0 = new byte[] {0x01, 0, 0, 0, 0, 0, 0, 0};

  private static final byte[] DATA_1_BYTE_64 = new byte[] {(byte) 0xC0};
  private static final byte[] DATA_2_BYTE_64 = new byte[] {0x40, 0x40};
  private static final byte[] DATA_3_BYTE_64 = new byte[] {0x20, 0, 0x40};
  private static final byte[] DATA_4_BYTE_64 = new byte[] {0x10, 0, 0, 0x40};
  private static final byte[] DATA_5_BYTE_64 = new byte[] {0x08, 0, 0, 0, 0x40};
  private static final byte[] DATA_6_BYTE_64 = new byte[] {0x04, 0, 0, 0, 0, 0x40};
  private static final byte[] DATA_7_BYTE_64 = new byte[] {0x02, 0, 0, 0, 0, 0, 0x40};
  private static final byte[] DATA_8_BYTE_64 = new byte[] {0x01, 0, 0, 0, 0, 0, 0, 0x40};

  private static final byte[] DATA_1_BYTE_MAX = new byte[] {MAX_BYTE};
  private static final byte[] DATA_2_BYTE_MAX = new byte[] {0x7F, MAX_BYTE};
  private static final byte[] DATA_3_BYTE_MAX = new byte[] {0x3F, MAX_BYTE, MAX_BYTE};
  private static final byte[] DATA_4_BYTE_MAX = new byte[] {0x1F, MAX_BYTE, MAX_BYTE, MAX_BYTE};
  private static final byte[] DATA_5_BYTE_MAX =
      new byte[] {0x0F, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE};
  private static final byte[] DATA_6_BYTE_MAX =
      new byte[] {0x07, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE};
  private static final byte[] DATA_7_BYTE_MAX =
      new byte[] {0x03, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE};
  private static final byte[] DATA_8_BYTE_MAX =
      new byte[] {0x01, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE, MAX_BYTE};

  private static final long VALUE_1_BYTE_MAX = 0x7F;
  private static final long VALUE_1_BYTE_MAX_WITH_MASK = 0xFF;
  private static final long VALUE_2_BYTE_MAX = 0x3FFF;
  private static final long VALUE_2_BYTE_MAX_WITH_MASK = 0x7FFF;
  private static final long VALUE_3_BYTE_MAX = 0x1FFFFF;
  private static final long VALUE_3_BYTE_MAX_WITH_MASK = 0x3FFFFF;
  private static final long VALUE_4_BYTE_MAX = 0xFFFFFFF;
  private static final long VALUE_4_BYTE_MAX_WITH_MASK = 0x1FFFFFFF;
  private static final long VALUE_5_BYTE_MAX = 0x7FFFFFFFFL;
  private static final long VALUE_5_BYTE_MAX_WITH_MASK = 0xFFFFFFFFFL;
  private static final long VALUE_6_BYTE_MAX = 0x3FFFFFFFFFFL;
  private static final long VALUE_6_BYTE_MAX_WITH_MASK = 0x7FFFFFFFFFFL;
  private static final long VALUE_7_BYTE_MAX = 0x1FFFFFFFFFFFFL;
  private static final long VALUE_7_BYTE_MAX_WITH_MASK = 0x3FFFFFFFFFFFFL;
  private static final long VALUE_8_BYTE_MAX = 0xFFFFFFFFFFFFFFL;
  private static final long VALUE_8_BYTE_MAX_WITH_MASK = 0x1FFFFFFFFFFFFFFL;

  @Test
  public void testReadVarintEndOfInputAtStart() throws IOException, InterruptedException {
    VarintReader reader = new VarintReader();
    // Build an input with no data.
    ExtractorInput input = new FakeExtractorInput.Builder()
        .setSimulateUnknownLength(true)
        .build();
    // End of input allowed.
    long result = reader.readUnsignedVarint(input, true, false, 8);
    assertThat(result).isEqualTo(RESULT_END_OF_INPUT);
    // End of input not allowed.
    try {
      reader.readUnsignedVarint(input, false, false, 8);
      fail();
    } catch (EOFException e) {
      // Expected.
    }
  }

  @Test
  public void testReadVarintExceedsMaximumAllowedLength() throws IOException, InterruptedException {
    VarintReader reader = new VarintReader();
    ExtractorInput input = new FakeExtractorInput.Builder()
        .setData(DATA_8_BYTE_0)
        .setSimulateUnknownLength(true)
        .build();
    long result = reader.readUnsignedVarint(input, false, true, 4);
    assertThat(result).isEqualTo(RESULT_MAX_LENGTH_EXCEEDED);
  }

  @Test
  public void testReadVarint() throws IOException, InterruptedException {
    VarintReader reader = new VarintReader();
    testReadVarint(reader, true, DATA_1_BYTE_0, 1, 0);
    testReadVarint(reader, true, DATA_2_BYTE_0, 2, 0);
    testReadVarint(reader, true, DATA_3_BYTE_0, 3, 0);
    testReadVarint(reader, true, DATA_4_BYTE_0, 4, 0);
    testReadVarint(reader, true, DATA_5_BYTE_0, 5, 0);
    testReadVarint(reader, true, DATA_6_BYTE_0, 6, 0);
    testReadVarint(reader, true, DATA_7_BYTE_0, 7, 0);
    testReadVarint(reader, true, DATA_8_BYTE_0, 8, 0);
    testReadVarint(reader, true, DATA_1_BYTE_64, 1, 64);
    testReadVarint(reader, true, DATA_2_BYTE_64, 2, 64);
    testReadVarint(reader, true, DATA_3_BYTE_64, 3, 64);
    testReadVarint(reader, true, DATA_4_BYTE_64, 4, 64);
    testReadVarint(reader, true, DATA_5_BYTE_64, 5, 64);
    testReadVarint(reader, true, DATA_6_BYTE_64, 6, 64);
    testReadVarint(reader, true, DATA_7_BYTE_64, 7, 64);
    testReadVarint(reader, true, DATA_8_BYTE_64, 8, 64);
    testReadVarint(reader, true, DATA_1_BYTE_MAX, 1, VALUE_1_BYTE_MAX);
    testReadVarint(reader, true, DATA_2_BYTE_MAX, 2, VALUE_2_BYTE_MAX);
    testReadVarint(reader, true, DATA_3_BYTE_MAX, 3, VALUE_3_BYTE_MAX);
    testReadVarint(reader, true, DATA_4_BYTE_MAX, 4, VALUE_4_BYTE_MAX);
    testReadVarint(reader, true, DATA_5_BYTE_MAX, 5, VALUE_5_BYTE_MAX);
    testReadVarint(reader, true, DATA_6_BYTE_MAX, 6, VALUE_6_BYTE_MAX);
    testReadVarint(reader, true, DATA_7_BYTE_MAX, 7, VALUE_7_BYTE_MAX);
    testReadVarint(reader, true, DATA_8_BYTE_MAX, 8, VALUE_8_BYTE_MAX);
    testReadVarint(reader, false, DATA_1_BYTE_MAX, 1, VALUE_1_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_2_BYTE_MAX, 2, VALUE_2_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_3_BYTE_MAX, 3, VALUE_3_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_4_BYTE_MAX, 4, VALUE_4_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_5_BYTE_MAX, 5, VALUE_5_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_6_BYTE_MAX, 6, VALUE_6_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_7_BYTE_MAX, 7, VALUE_7_BYTE_MAX_WITH_MASK);
    testReadVarint(reader, false, DATA_8_BYTE_MAX, 8, VALUE_8_BYTE_MAX_WITH_MASK);
  }

  @Test
  public void testReadVarintFlaky() throws IOException, InterruptedException {
    VarintReader reader = new VarintReader();
    testReadVarintFlaky(reader, true, DATA_1_BYTE_0, 1, 0);
    testReadVarintFlaky(reader, true, DATA_2_BYTE_0, 2, 0);
    testReadVarintFlaky(reader, true, DATA_3_BYTE_0, 3, 0);
    testReadVarintFlaky(reader, true, DATA_4_BYTE_0, 4, 0);
    testReadVarintFlaky(reader, true, DATA_5_BYTE_0, 5, 0);
    testReadVarintFlaky(reader, true, DATA_6_BYTE_0, 6, 0);
    testReadVarintFlaky(reader, true, DATA_7_BYTE_0, 7, 0);
    testReadVarintFlaky(reader, true, DATA_8_BYTE_0, 8, 0);
    testReadVarintFlaky(reader, true, DATA_1_BYTE_64, 1, 64);
    testReadVarintFlaky(reader, true, DATA_2_BYTE_64, 2, 64);
    testReadVarintFlaky(reader, true, DATA_3_BYTE_64, 3, 64);
    testReadVarintFlaky(reader, true, DATA_4_BYTE_64, 4, 64);
    testReadVarintFlaky(reader, true, DATA_5_BYTE_64, 5, 64);
    testReadVarintFlaky(reader, true, DATA_6_BYTE_64, 6, 64);
    testReadVarintFlaky(reader, true, DATA_7_BYTE_64, 7, 64);
    testReadVarintFlaky(reader, true, DATA_8_BYTE_64, 8, 64);
    testReadVarintFlaky(reader, true, DATA_1_BYTE_MAX, 1, VALUE_1_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_2_BYTE_MAX, 2, VALUE_2_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_3_BYTE_MAX, 3, VALUE_3_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_4_BYTE_MAX, 4, VALUE_4_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_5_BYTE_MAX, 5, VALUE_5_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_6_BYTE_MAX, 6, VALUE_6_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_7_BYTE_MAX, 7, VALUE_7_BYTE_MAX);
    testReadVarintFlaky(reader, true, DATA_8_BYTE_MAX, 8, VALUE_8_BYTE_MAX);
    testReadVarintFlaky(reader, false, DATA_1_BYTE_MAX, 1, VALUE_1_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_2_BYTE_MAX, 2, VALUE_2_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_3_BYTE_MAX, 3, VALUE_3_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_4_BYTE_MAX, 4, VALUE_4_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_5_BYTE_MAX, 5, VALUE_5_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_6_BYTE_MAX, 6, VALUE_6_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_7_BYTE_MAX, 7, VALUE_7_BYTE_MAX_WITH_MASK);
    testReadVarintFlaky(reader, false, DATA_8_BYTE_MAX, 8, VALUE_8_BYTE_MAX_WITH_MASK);
  }

  private static void testReadVarint(VarintReader reader, boolean removeMask, byte[] data,
      int expectedLength, long expectedValue) throws IOException, InterruptedException {
    ExtractorInput input = new FakeExtractorInput.Builder()
        .setData(data)
        .setSimulateUnknownLength(true)
        .build();
    long result = reader.readUnsignedVarint(input, false, removeMask, 8);
    assertThat(input.getPosition()).isEqualTo(expectedLength);
    assertThat(result).isEqualTo(expectedValue);
  }

  private static void testReadVarintFlaky(VarintReader reader, boolean removeMask, byte[] data,
      int expectedLength, long expectedValue) throws IOException, InterruptedException {
    ExtractorInput input = new FakeExtractorInput.Builder()
        .setData(data)
        .setSimulateUnknownLength(true)
        .setSimulateIOErrors(true)
        .setSimulatePartialReads(true)
        .build();
    long result = -1;
    while (result == -1) {
      try {
        result = reader.readUnsignedVarint(input, false, removeMask, 8);
        if (result == C.RESULT_END_OF_INPUT || result == C.RESULT_MAX_LENGTH_EXCEEDED) {
          // Unexpected.
          fail();
        }
      } catch (SimulatedIOException e) {
        // Expected.
      }
    }
    assertThat(input.getPosition()).isEqualTo(expectedLength);
    assertThat(result).isEqualTo(expectedValue);
  }

}