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Validating Linked List Merge Sort Implementation in JCSprout

This test suite validates the implementation of a merge sort algorithm for linked lists, focusing on edge cases and sorting functionality. The tests ensure proper handling of null inputs, boundary conditions, and verify the correct ordering of elements in the sorted linked list.

Test Coverage Overview

The test suite provides comprehensive coverage of the LinkedListMergeSort implementation:

Constructor initialization validation
Merge operation with various node combinations
Null input handling for both left and right nodes
Boundary value testing with Integer.MIN_VALUE
Sort operation verification for different list lengths

Implementation Analysis

The testing approach employs JUnit 4 framework features with systematic test organization:

Global timeout rule implementation
Arrange-Act-Assert pattern usage
Explicit test case naming conventions
Comprehensive assertion chains for node validation

Technical Details

Testing infrastructure includes:

JUnit 4 testing framework
Timeout rule for performance boundaries
Custom Node class testing
Assert class for validation checks

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Isolated test cases for each scenario
Clear test method naming conventions
Thorough null checking and edge case handling
Consistent test structure and organization
Proper boundary value testing

crossoverjie/jcsprout

src/test/java/com/crossoverjie/algorithm/LinkedListMergeSortTest.java

            
package com.crossoverjie.algorithm;

import org.junit.Assert;
import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.Timeout;


public class LinkedListMergeSortTest {

  @Rule public Timeout globalTimeout = new Timeout(10000);

  @Test
  public void constructorOutputVoid() {

    // Act, creating object to test constructor
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();

    // Method returns void, testing that no exception is thrown
  }

  // Test generated by Diffblue Cover.
  @Test
  public void mergeListNotNull() {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node left = new LinkedListMergeSort.Node(-2_147_483_647, null);
    final LinkedListMergeSort.Node right = new LinkedListMergeSort.Node(0, null);

    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeList(left, right);

    // Assert result
    Assert.assertNotNull(retval);
    Assert.assertEquals(0, retval.e);
    Assert.assertNotNull(retval.next);
    Assert.assertEquals(-2_147_483_647, retval.next.e);
    Assert.assertNull(retval.next.next);
  }

  // Test generated by Diffblue Cover.
  @Test
  public void mergeListInputNotNullNotNullOutputNotNull2() {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node left = new LinkedListMergeSort.Node(1, null);
    final LinkedListMergeSort.Node right = new LinkedListMergeSort.Node(-2_147_483_648, null);

    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeList(left, right);


    // Assert result
    Assert.assertNotNull(retval);
    Assert.assertEquals(1, retval.e);
    Assert.assertNotNull(retval.next);
    Assert.assertEquals(-2_147_483_648, retval.next.e);
    Assert.assertNull(retval.next.next);
  }


  @Test
  public void mergeListInputRightNull()  {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node left = new LinkedListMergeSort.Node(-2_147_483_647,null);
    final LinkedListMergeSort.Node right = null;


    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeList(left, right);

    // Assert result
    Assert.assertNotNull(retval);
    Assert.assertEquals(-2_147_483_647, retval.e);
    Assert.assertNull(retval.next);
  }


  @Test
  public void mergeListInputLeftNull()  {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node left = null;
    final LinkedListMergeSort.Node right = new LinkedListMergeSort.Node(0, null);


    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeList(left, right);

    // Assert result
    Assert.assertNotNull(retval);
    Assert.assertEquals(0, retval.e);
    Assert.assertNull(retval.next);
  }


  @Test
  public void mergeListInputNull() {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node left = null;
    final LinkedListMergeSort.Node right = null;

    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeList(left, right);

    // Assert result
    Assert.assertNull(retval);
  }

  @Test
  public void mergeSortLength2() {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node node =  new LinkedListMergeSort.Node(-0, null);
    final LinkedListMergeSort.Node first = new LinkedListMergeSort.Node(-2_147_483_647, node);

    final int length = 2;

    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeSort(first, length);

    // Assert result
    Assert.assertNotNull(retval);
    Assert.assertEquals(0, retval.e);
    Assert.assertNotNull(retval.next);
    Assert.assertEquals(-2_147_483_647, retval.next.e);
    Assert.assertNull(retval.next.next);
  }

  @Test
  public void mergeSortInputNull() {

    // Arrange
    final LinkedListMergeSort objectUnderTest = new LinkedListMergeSort();
    final LinkedListMergeSort.Node first = null;
    final int length = 1;

    // Act
    final LinkedListMergeSort.Node retval = objectUnderTest.mergeSort(first, length);

    // Assert result
    Assert.assertNull(retval);
  }
  @Test
  public void mainInput0OutputVoid() throws Exception {

    // Arrange
    final String[] args = {};

    // Act
    LinkedListMergeSort.main(args);

    // Method returns void, testing that no exception is thrown
  }

}