coding-practice/problems/1792-maximum-average-pass-ratio/test/SolutionTests.cs

// LeetCode 1792 單元測試
// 使用 xUnit 框架

using Xunit;
using System;
using System.Collections.Generic;

public class SolutionTests
{
    private readonly Solution _solution;
    private const double TOLERANCE = 0.00001;

    public SolutionTests()
    {
        _solution = new Solution();
    }

    #region Basic Test
    [Fact]
    public void TestCase1()
    {
        // Arrange
        int[][] classes = new int[][]
        {
            new int[] {1, 2},
            new int[] {3, 5},
            new int[] {2, 2}
        };
        int extraStudents = 2;
        double expected = 0.78333;

        // Act
        var result = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        Assert.True(Math.Abs(result - expected) < TOLERANCE,
            $"Expected: {expected}, Actual: {result}");
    }

    [Fact]
    public void TestCase2()
    {

        // Arrange
        int[][] classes = new int[][]
        {
            new int[] {2, 4},   // 通過率: 2/4 = 0.5
            new int[] {3, 9},   // 通過率: 3/9 = 0.333...
            new int[] {4, 5},   // 通過率: 4/5 = 0.8
            new int[] {2, 10}   // 通過率: 2/10 = 0.2
        };
        int extraStudents = 4;
        double expected = 0.53485;

        // Act
        var result = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        Assert.True(Math.Abs(result - expected) < TOLERANCE,
            $"Expected: {expected}, Actual: {result}");
    }

    [Fact]
    public void TestBruteForceVsPriorityQueue()
    {
        // Arrange
        int[][] classes = new int[][]
        {
            new int[] {1, 3},
            new int[] {2, 4},
            new int[] {1, 5}
        };
        int extraStudents = 3;

        // Act
        var resultBruteForce = _solution.MaxAverageRatioByBruteForce(classes, extraStudents);
        var resultPriorityQueue = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        Assert.True(Math.Abs(resultBruteForce - resultPriorityQueue) < TOLERANCE,
            $"Brute Force: {resultBruteForce}, Priority Queue: {resultPriorityQueue}");
    }
    #endregion

    #region Edge Test
    [Fact]
    public void TestEdgeCases_MinClassesLength_OneClass()
    {
        // Arrange
        int[][] classes = new int[][]
        {
            new int[] {50, 100}
        };
        int extraStudents = 10;
        double expected = 60.0 / 110.0;

        // Act
        var result = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        Assert.True(result >= 0 && result <= 1,
            $"Result should be between 0 and 1, got: {result}");
        Assert.True(Math.Abs(result - expected) < TOLERANCE,
            $"Expected: {expected}, Actual: {result}");
    }

    [Fact]
    public void TestEdgeCases_LargeClassesLength()
    {
        // Arrange
        const int numClasses = 1000;
        var classes = new int[numClasses][];
        var random = new Random(42);

        for (int i = 0; i < numClasses; i++)
        {
            int total = random.Next(10, 100);  // total 在 10-100 之間
            int pass = random.Next(1, total + 1);  // pass 在 1-total 之間
            classes[i] = new int[] { pass, total };
        }
        int extraStudents = 100;

        // Act
        var result = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        Assert.True(result >= 0 && result <= 1,
            $"Result should be between 0 and 1, got: {result}");
    }

    [Fact]
    public void TestEdgeCases_MinExtraStudents_One()
    {
        // Arrange
        int[][] classes = new int[][]
        {
            new int[] {1, 3},
            new int[] {2, 4}
        };
        int extraStudents = 1;

        // Act
        var result = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        double originalAvg = (1.0 / 3 + 2.0 / 4) / 2;
        Assert.True(result > originalAvg,
            $"Result {result} should be greater than original average {originalAvg}");
    }

    [Fact]
    public void TestEdgeCases_LargeExtraStudents()
    {
        // Arrange - 大量額外學生
        int[][] classes = new int[][]
        {
            new int[] {10, 100},  // 10% 通過率
            new int[] {20, 100},  // 20% 通過率
            new int[] {30, 100}   // 30% 通過率
        };
        int extraStudents = 10000;

        // Act
        var result = _solution.MaxAverageRatio(classes, extraStudents);

        // Assert
        Assert.True(result >= 0 && result <= 1, 
            $"Result should be between 0 and 1, got: {result}");
        
        // 大量學生加入後，通過率應該顯著提升
        double originalAvg = (0.1 + 0.2 + 0.3) / 3; // = 0.2
        Assert.True(result > originalAvg + 0.1, 
            $"Result {result} should be significantly higher than original average {originalAvg}");
    }
    #endregion
}