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https://github.com/emadb/password_validator_kata

The Password Validation Kata in Elixir
https://github.com/emadb/password_validator_kata

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The Password Validation Kata in Elixir

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# Password Validation Kata
Taken from [Codurance](https://www.codurance.com/katas/password-validation)

_Resolved in [Elixir](https://elixir-lang.org) using recursion (no loops!) an a functional approach. Each validator is a pure function._

## Iteration 1 - Basic password validation

### Goal

Design and implement a software that validates a password applying TDD.

The password will be introduced by the user (as an argument of the method) and should return if the password is valid or not.

A valid password should meet the following requirements:

* Have more than 8 characters
* Contains a capital letter
* Contains a lowercase
* Contains a number
* Contains an underscore


## Technical requirements:

* We want a method that answers if the password is valid or not.
* We don't want to know the reason when the password is invalid (the return value is a boolean)


## Iteration 2 - Rules abstraction

### Goal

Design and implement software that can adapt to different password validation rules TDD and focus on the OOP principles.

Let's pretend that now we want to create another type of password validations because on our app we need different type of passwords, such as:

Validation 2:

* Have more than 6 characters
* Contains a capital letter
* Contains a lowercase
* Contains a number


Validation 3:

* Have more than 16 characters
* Contains a capital letter
* Contains a lowercase
* Contains an underscore


### Things to practice

In this iteration, we should try to identify a good abstraction and try to work on OOP principles as well as on design patterns like Builder and Factory

### Interesting restrictions

Use object calisthenics.

## Iteration 3 - Multiple errors

### Goal

Now we can know if a password is valid or not, but we cannot understand why, in this iteration, we should be able to return a list of errors for each invalid password, so we could know why the password it's not valid.

### Things to practice

Identify how maintainable it's the code that you've built so far, and how it adapts to change, this iteration could change depending on the programming language that you use.

## Iteration 4 - Validation strategy

### Goal

Up untill this point we've been able to create a list of validation rules and validate the password passes all the validation rules, but now we want a new password with the same rules but allowing to fail only one of them.

Validation 4

* Have more than 8 characters
* Contains a capital letter
* Contains a number
* Contains an underscore


Examples:

* Have more than 8 characters ✅
* Contains a capital letter ✅
* Contains a number ✅
* Contains an underscore ❌


This password it's a valid password

### Things to practice

This will help to enforce encapsulation for the lists of rules and have a better design for validation strategies [preventing us from using inheritance], this also could help us work on the Strategy pattern.