services:
  mongo:
    image: mongo:6.0
    command: mongod --setParameter enableTestCommands=1
    ports:
      - "27017:27017"
    environment:
      MONGO_INITDB_ROOT_USERNAME: root
      MONGO_INITDB_ROOT_PASSWORD: password

use admin;
db.runCommand({
  configureFailPoint: "failCommand",
  mode: { times: 1 },
  data: {
    failCommands: ["createIndexes"],
    errorCode: 100,
    closeConnection: false
  }
});

use admin;
db.runCommand({
  configureFailPoint: "failCommand",
  mode: "off"
});

[SetUp]  
public void Setup()  
{  
    // Подключаемся к локальной монге, где включены testCommands  
    var client = new MongoClient("mongodb://root:password@localhost:27017");  
    _database = client.GetDatabase("testDb");  
    _collection = _database.GetCollection<BsonDocument>("testCollection");  
    _adminDatabase = client.GetDatabase("admin");  
  
    // Включаем FailPoint для команды createIndexes  
    var enableFailPoint = new BsonDocument  
    {  
        { "configureFailPoint", "failCommand" },  
        { "mode", new BsonDocument("times", 1) },  
        {  
            "data", new BsonDocument  
            {  
                { "failCommands", new BsonArray { "createIndexes" } },  
                { "errorCode", 100 }, // код ошибки (для проверки)  
                { "closeConnection", false } // соединение не рвём  
            }  
        }  
    };  
  
    _adminDatabase.RunCommand<BsonDocument>(enableFailPoint);  
}

[Test]  
public void CreateIndexes_ShouldThrowException_WhenFailPointEnabled()  
{  
    var ex = Assert.Throws<MongoCommandException>(() =>  
    {  
        _collection.Indexes.CreateOne(  
            new CreateIndexModel<BsonDocument>(  
                Builders<BsonDocument>.IndexKeys.Ascending("someField")));  
    });  
  
    Assert.That(ex.Code, Is.EqualTo(100));  
}

[TearDown]  
public void TearDown()  
{  
    // Выключаем FailPoint, чтобы вернуть MongoDb в исходное состояние  
    var disableFailPoint = new BsonDocument  
    {  
        { "configureFailPoint", "failCommand" },  
        { "mode", "off" }  
    };  
  
    _adminDatabase.RunCommand<BsonDocument>(disableFailPoint);  
}

var functions = new List<Func<int, int>>();

for (int i = 0; i < 10; i++)
{
    Func<int, int> function = x => i * x;
    if (!functions.Contains(function))
    {
        functions.Add(function);
    }
}

Console.WriteLine(functions.Count);