coding-practice/problems/3025-find-the-number-of-ways-to-place-people-i/test/SolutionTests.cs

// LeetCode 3025 單元測試
// 使用 xUnit 框架

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

public class SolutionTests
{
    private readonly Solution _solution;

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

    [Fact]
    public void TestCase1_ExampleFromProblem()
    {
        // Arrange
        int[][] points = new int[][] {
            new int[] {6, 2},
            new int[] {4, 4},
            new int[] {2, 6}
        };
        int expected = 2;

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestCase2_TwoPoints()
    {
        // Arrange
        int[][] points = new int[][] {
            new int[] {1, 3},
            new int[] {2, 1}
        };
        int expected = 1;

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestCase3_NoValidPairs()
    {
        // Arrange - 沒有有效點對的情況
        int[][] points = new int[][] {
            new int[] {1, 1},
            new int[] {2, 2},
            new int[] {3, 3}
        };
        int expected = 0;

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestCase4_SameXCoordinate()
    {
        // Arrange - x 座標相同的情況
        int[][] points = new int[][] {
            new int[] {3, 5},
            new int[] {3, 2},
            new int[] {3, 1}
        };
        int expected = 2;

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestCase5_SameYCoordinate()
    {
        // Arrange - y 座標相同的情況
        int[][] points = new int[][] {
            new int[] {1, 4},
            new int[] {3, 4},
            new int[] {5, 4}
        };
        int expected = 2;

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestCase6_PointsInsideRectangle()
    {
        // Arrange - 矩形內有其他點的情況
        int[][] points = new int[][] {
            new int[] {0, 4},    // A
            new int[] {4, 0},    // B  
            new int[] {2, 2}     // C (在 A-B 矩形內)
        };

        int expected = 2;

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestCase7_PointsOnBorder()
    {
        // Arrange - 點在矩形邊界上的情況
        int[][] points = new int[][] {
            new int[] {0, 3},    // A
            new int[] {3, 0},    // B
            new int[] {0, 0}     // C (在矩形邊界上)
        };
        int expected = 2; // (A,C) 和 (C,B) 有效

        // Act
        var result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestEdgeCases_MinimumPoints()
    {
        // Arrange - 最少點數情況 (題目限制 n >= 2)
        int[][] points = new int[][] {
            new int[] {0, 1},
            new int[] {1, 0}
        };
        int expected = 1; // (0,1) 在 (1,0) 的左上方

        // Act
        int result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestEdgeCases_IdenticalCoordinates()
    {
        // Arrange - 座標值相同的情況
        int[][] points = new int[][] {
            new int[] {2, 2},
            new int[] {2, 2}  // 題目保證所有點都不同，但測試邊界
        };

        // 這個測試案例實際上違反了題目條件 (All points[i] are distinct)
        // 但可以測試程式的健壯性
        int expected = 2; // 兩個相同點互相滿足左上方條件

        // Act
        int result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestEdgeCases_MaxCoordinateValues()
    {
        // Arrange - 最大座標值情況 (題目限制 0 <= coordinates <= 50)
        int[][] points = new int[][] {
            new int[] {0, 50},
            new int[] {50, 0},
            new int[] {25, 25}
        };
        int expected = 2; // (A,C) 和 (C,B) 有效

        // Act
        int result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestEdgeCases_EmptyArray()
    {
        // Arrange - 空陣列情況
        int[][] points = new int[0][];
        int expected = 0;

        // Act
        int result = _solution.NumberOfPairs(points);

        // Assert
        Assert.Equal(expected, result);
    }

    [Fact]
    public void TestEdgeCases_MaxPoints_AllDistinct_RandomPattern() {
        // Arrange - 50個不同的點，更複雜的模式
        var points = new List<int[]>();

        // 創建一個螺旋模式的50個不同點，確保都在 [0,50] 範圍內且互不相同
        var usedPoints = new HashSet<string>();
        var random = new Random(42); // 固定種子確保測試可重現

        while (points.Count < 50) {
            int x = random.Next(0, 51); // 0-50
            int y = random.Next(0, 51); // 0-50
            string pointKey = $"{x},{y}";

            if (!usedPoints.Contains(pointKey)) {
                usedPoints.Add(pointKey);
                points.Add(new int[] { x, y });
            }
        }
        
        int[][] pointsArray = points.ToArray();
        
        // 由於是隨機分佈，很難預測確切結果，但應該是一個合理的正數
        // 這個測試主要驗證程式在最大輸入時不會崩潰或超時
        
        // Act
        int result = _solution.NumberOfPairs(pointsArray);
        
        // Assert
        Assert.True(result >= 0); // 至少結果應該是非負數
        Assert.True(result <= 50 * 49); // 最多不會超過所有可能的點對
    }
}