Back to Repositories

Testing SequenceGroup Operations and Concurrent Modifications in LMAX-Disruptor

This test suite validates the functionality of the SequenceGroup class in the LMAX Disruptor, a high-performance inter-thread messaging library. The tests verify sequence group operations, management of multiple sequences, and concurrent modifications in a ring buffer context.

Test Coverage Overview

The test suite provides comprehensive coverage of SequenceGroup operations:

Empty group behavior and initialization
Adding and removing sequences
Minimum sequence reporting
Group size management
Concurrent modification scenarios
Sequence value synchronization

Edge cases include empty groups, duplicate sequence additions, and non-existent sequence removal.

Implementation Analysis

The testing approach uses JUnit Jupiter framework with a systematic verification of SequenceGroup’s core functionalities. The implementation employs both standard assertions and hamcrest matchers for validation, demonstrating various sequence manipulation patterns and thread-safe operations.

The tests follow a clear arrange-act-assert pattern, with careful attention to state verification after each operation.

Technical Details

Testing tools and configuration:

JUnit Jupiter test framework
Hamcrest matchers for assertions
RingBuffer implementation for concurrent testing
TestEvent factory for event generation
Custom Sequence class integration

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test methods with clear naming conventions
Comprehensive edge case coverage
Proper test setup and teardown
Effective use of assertion libraries
Concurrent modification testing
Clear separation of concerns in test scenarios

lmax-exchange/disruptor

src/test/java/com/lmax/disruptor/SequenceGroupTest.java

            
/*
 * Copyright 2011 LMAX Ltd.
 *
 * 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.lmax.disruptor;

import com.lmax.disruptor.support.TestEvent;
import org.junit.jupiter.api.Test;

import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

public final class SequenceGroupTest
{
    @Test
    public void shouldReturnMaxSequenceWhenEmptyGroup()
    {
        final SequenceGroup sequenceGroup = new SequenceGroup();
        assertEquals(Long.MAX_VALUE, sequenceGroup.get());
    }

    @Test
    public void shouldAddOneSequenceToGroup()
    {
        final Sequence sequence = new Sequence(7L);
        final SequenceGroup sequenceGroup = new SequenceGroup();

        sequenceGroup.add(sequence);

        assertEquals(sequence.get(), sequenceGroup.get());
    }

    @Test
    public void shouldNotFailIfTryingToRemoveNotExistingSequence() throws Exception
    {
        SequenceGroup group = new SequenceGroup();
        group.add(new Sequence());
        group.add(new Sequence());
        group.remove(new Sequence());
    }

    @Test
    public void shouldReportTheMinimumSequenceForGroupOfTwo()
    {
        final Sequence sequenceThree = new Sequence(3L);
        final Sequence sequenceSeven = new Sequence(7L);
        final SequenceGroup sequenceGroup = new SequenceGroup();

        sequenceGroup.add(sequenceSeven);
        sequenceGroup.add(sequenceThree);

        assertEquals(sequenceThree.get(), sequenceGroup.get());
    }

    @Test
    public void shouldReportSizeOfGroup()
    {
        final SequenceGroup sequenceGroup = new SequenceGroup();
        sequenceGroup.add(new Sequence());
        sequenceGroup.add(new Sequence());
        sequenceGroup.add(new Sequence());

        assertEquals(3, sequenceGroup.size());
    }

    @Test
    public void shouldRemoveSequenceFromGroup()
    {
        final Sequence sequenceThree = new Sequence(3L);
        final Sequence sequenceSeven = new Sequence(7L);
        final SequenceGroup sequenceGroup = new SequenceGroup();

        sequenceGroup.add(sequenceSeven);
        sequenceGroup.add(sequenceThree);

        assertEquals(sequenceThree.get(), sequenceGroup.get());

        assertTrue(sequenceGroup.remove(sequenceThree));
        assertEquals(sequenceSeven.get(), sequenceGroup.get());
        assertEquals(1, sequenceGroup.size());
    }

    @Test
    public void shouldRemoveSequenceFromGroupWhereItBeenAddedMultipleTimes()
    {
        final Sequence sequenceThree = new Sequence(3L);
        final Sequence sequenceSeven = new Sequence(7L);
        final SequenceGroup sequenceGroup = new SequenceGroup();

        sequenceGroup.add(sequenceThree);
        sequenceGroup.add(sequenceSeven);
        sequenceGroup.add(sequenceThree);

        assertEquals(sequenceThree.get(), sequenceGroup.get());

        assertTrue(sequenceGroup.remove(sequenceThree));
        assertEquals(sequenceSeven.get(), sequenceGroup.get());
        assertEquals(1, sequenceGroup.size());
    }

    @Test
    public void shouldSetGroupSequenceToSameValue()
    {
        final Sequence sequenceThree = new Sequence(3L);
        final Sequence sequenceSeven = new Sequence(7L);
        final SequenceGroup sequenceGroup = new SequenceGroup();

        sequenceGroup.add(sequenceSeven);
        sequenceGroup.add(sequenceThree);

        final long expectedSequence = 11L;
        sequenceGroup.set(expectedSequence);

        assertEquals(expectedSequence, sequenceThree.get());
        assertEquals(expectedSequence, sequenceSeven.get());
    }

    @Test
    public void shouldAddWhileRunning() throws Exception
    {
        RingBuffer<TestEvent> ringBuffer = RingBuffer.createSingleProducer(TestEvent.EVENT_FACTORY, 32);
        final Sequence sequenceThree = new Sequence(3L);
        final Sequence sequenceSeven = new Sequence(7L);
        final SequenceGroup sequenceGroup = new SequenceGroup();
        sequenceGroup.add(sequenceSeven);

        for (int i = 0; i < 11; i++)
        {
            ringBuffer.publish(ringBuffer.next());
        }

        sequenceGroup.addWhileRunning(ringBuffer, sequenceThree);
        assertThat(sequenceThree.get(), is(10L));
    }
}