func TestDivide(t *testing.T) {
    tests := []struct {
        name     string
        a, b     int
        want     int
        hasError bool
    }{
        {"正常除法", 10, 2, 5, false},
        {"除以1", 7, 1, 7, false},
        {"被除数为0", 0, 3, 0, false},
        {"除以0", 5, 0, 0, true},  // 边界：除数为0
        {"最小整数除以-1", math.MinInt32, -1, 0, true}, // 溢出边界
        {"刚好整除", 9, 3, 3, false},
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got, err := Divide(tt.a, tt.b)
            if tt.hasError {
                if err == nil {
                    t.Fatalf("expected error but got none")
                }
                return
            }
            if err != nil {
                t.Fatalf("unexpected error: %v", err)
            }
            if got != tt.want {
                t.Errorf("got %d, want %d", got, tt.want)
            }
        })
    }
}

func TestFirstElement(t *testing.T) {
    tests := []struct {
        name string
        input []int
        want  int
        valid bool
    }{
        {"非空切片", []int{1, 2, 3}, 1, true},
        {"单元素", []int{42}, 42, true},
        {"空切片", nil, 0, false},   // 边界
        {"空切片{}", []int{}, 0, false}, // 边界
    }

    for _, tt := range tests {
        got, ok := FirstElement(tt.input)
        if tt.valid != ok {
            t.Errorf("%s: expected ok=%v, got %v", tt.name, tt.valid, ok)
        }
        if tt.valid && got != tt.want {
            t.Errorf("%s: got %d, want %d", tt.name, got, tt.want)
        }
    }
}