diff --git a/requirements.txt b/requirements.txt
index e3a46cb..9a6c85a 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,28 +1,2 @@
-bleach==4.1.0
-certifi==2023.7.22
-cffi==1.15.0
-charset-normalizer==2.0.7
-colorama==0.4.4
-coverage==6.0.2
-cryptography==39.0.1
-docutils==0.18
-idna==3.3
-importlib-metadata==4.8.1
-jeepney==0.7.1
-keyring==23.2.1
-packaging==21.0
-pkginfo==1.7.1
-pycparser==2.20
-Pygments==2.10.0
-pyparsing==3.0.2
-readme-renderer==30.0
-requests==2.26.0
-requests-toolbelt==0.9.1
-rfc3986==1.5.0
-SecretStorage==3.3.1
-six==1.16.0
-tqdm==4.62.3
-twine==3.4.2
-urllib3==1.26.7
-webencodings==0.5.1
-zipp==3.6.0
+pytest==7.4.4
+pytest-cov==4.1.0
diff --git a/setup.py b/setup.py
index 8e0a8e4..0239f29 100644
--- a/setup.py
+++ b/setup.py
@@ -1,7 +1,6 @@
 import setuptools
 
-
-with open("README.md", "r") as fh:
+with open("README.md") as fh:
     long_description = fh.read()
 
 setuptools.setup(
diff --git a/validate_docbr/BaseDoc.py b/validate_docbr/BaseDoc.py
index bd437eb..3f5f47b 100644
--- a/validate_docbr/BaseDoc.py
+++ b/validate_docbr/BaseDoc.py
@@ -1,10 +1,11 @@
-from abc import ABC
+from abc import ABC, abstractmethod
 from typing import List
 
 
 class BaseDoc(ABC):
     """Classe base para todas as classes referentes a documentos."""
 
+    @abstractmethod
     def validate(self, doc: str = '') -> bool:
         """Método para validar o documento desejado."""
         pass
@@ -13,18 +14,24 @@ def validate_list(self, docs: List[str]) -> List[bool]:
         """Método para validar uma lista de documentos desejado."""
         return [self.validate(doc) for doc in docs]
 
+    @abstractmethod
     def generate(self, mask: bool = False) -> str:
         """Método para gerar um documento válido."""
         pass
 
-    def generate_list(self, n: int = 1, mask: bool = False, repeat: bool = False) -> list:
+    def generate_list(
+        self,
+        n: int = 1,
+        mask: bool = False,
+        repeat: bool = False
+    ) -> list:
         """Gerar uma lista do mesmo documento."""
         doc_list = []
 
         if n <= 0:
             return doc_list
 
-        for i in range(n):
+        for _ in range(n):
             doc_list.append(self.generate(mask))
 
         while not repeat:
@@ -32,24 +39,30 @@ def generate_list(self, n: int = 1, mask: bool = False, repeat: bool = False) ->
             unique_values = len(doc_set)
 
             if unique_values < n:
-                doc_list = list(doc_set) + self.generate_list((n - unique_values), mask, repeat)
+                doc_list = list(doc_set) + self.generate_list(
+                    (n - unique_values),
+                    mask,
+                    repeat
+                )
             else:
                 repeat = True
 
         return doc_list
 
+    @abstractmethod
     def mask(self, doc: str = '') -> str:
         """Mascara o documento enviado"""
         pass
 
     def _only_digits(self, doc: str = '') -> str:
         """Remove os outros caracteres que não sejam dígitos."""
-        return "".join([x for x in doc if x.isdigit()])
+        return ''.join([x for x in doc if x.isdigit()])
 
     def _validate_input(self, input: str, valid_characters: List = None) -> bool:
         """Validar input.
         Caso ele possua apenas dígitos e caracteres válidos, retorna True.
-        Caso possua algum caractere que não seja dígito ou caractere válido, retorna False."""
+        Caso possua algum caractere que não seja dígito ou caractere válido,
+        retorna False."""
         if valid_characters is None:
             valid_characters = ['.', '-', '/', ' ']
 
diff --git a/validate_docbr/CNH.py b/validate_docbr/CNH.py
index 39b23b0..bb2a603 100644
--- a/validate_docbr/CNH.py
+++ b/validate_docbr/CNH.py
@@ -1,7 +1,8 @@
-from .BaseDoc import BaseDoc
 from random import sample
 from typing import Union
 
+from .BaseDoc import BaseDoc
+
 
 class CNH(BaseDoc):
     """Classe referente ao Carteira Nacional de Habilitação (CNH)."""
@@ -35,7 +36,7 @@ def generate(self, mask: bool = False) -> str:
 
     def mask(self, doc: str = '') -> str:
         """Coloca a máscara de CNH na variável doc."""
-        return "{} {} {} {}".format(doc[:3], doc[3:6], doc[6:9], doc[9:])
+        return f"{doc[:3]} {doc[3:6]} {doc[6:9]} {doc[9:]}"
 
     def _generate_first_digit(self, doc: Union[str, list]) -> str:
         """Gerar o primeiro dígito verificador da CNH."""
diff --git a/validate_docbr/CNPJ.py b/validate_docbr/CNPJ.py
index 1bac731..004679b 100644
--- a/validate_docbr/CNPJ.py
+++ b/validate_docbr/CNPJ.py
@@ -1,7 +1,8 @@
-from .BaseDoc import BaseDoc
 from random import sample
 from typing import Union
 
+from .BaseDoc import BaseDoc
+
 
 class CNPJ(BaseDoc):
     """Classe referente ao Cadastro Nacional da Pessoa Jurídica (CNPJ)."""
@@ -21,11 +22,7 @@ def validate(self, doc: str = '') -> bool:
         if len(doc) != 14:
             return False
 
-        for i in range(10):
-            if doc.count("{}".format(i)) == 14:
-                return False
-
-        return self._generate_first_digit(doc) == doc[12]\
+        return self._generate_first_digit(doc) == doc[12] \
                and self._generate_second_digit(doc) == doc[13]
 
     def generate(self, mask: bool = False) -> str:
@@ -43,7 +40,7 @@ def generate(self, mask: bool = False) -> str:
 
     def mask(self, doc: str = '') -> str:
         """Coloca a máscara de CNPJ na variável doc."""
-        return "{}.{}.{}/{}-{}".format(doc[:2], doc[2:5], doc[5:8], doc[8:12], doc[-2:])
+        return f"{doc[:2]}.{doc[2:5]}.{doc[5:8]}/{doc[8:12]}-{doc[-2:]}"
 
     def _generate_first_digit(self, doc: Union[str, list]) -> str:
         """Gerar o primeiro dígito verificador do CNPJ."""
@@ -53,11 +50,7 @@ def _generate_first_digit(self, doc: Union[str, list]) -> str:
             sum += int(doc[i]) * self.weights_first[i]
 
         sum = sum % 11
-
-        if sum < 2:
-            sum = 0
-        else:
-            sum = 11 - sum
+        sum = 0 if sum < 2 else 11 - sum
 
         return str(sum)
 
@@ -69,10 +62,6 @@ def _generate_second_digit(self, doc: Union[str, list]) -> str:
             sum += int(doc[i]) * self.weights_second[i]
 
         sum = sum % 11
-
-        if sum < 2:
-            sum = 0
-        else:
-            sum = 11 - sum
+        sum = 0 if sum < 2 else 11 - sum
 
         return str(sum)
diff --git a/validate_docbr/CNS.py b/validate_docbr/CNS.py
index 6809867..242833e 100644
--- a/validate_docbr/CNS.py
+++ b/validate_docbr/CNS.py
@@ -1,6 +1,7 @@
-from .BaseDoc import BaseDoc
 from random import sample
 
+from .BaseDoc import BaseDoc
+
 
 class CNS(BaseDoc):
     """Classe referente ao Cartão Nacional de Saúde (CNS)."""
@@ -44,13 +45,13 @@ def generate(self, mask: bool = False) -> str:
         else:
             cns = self._generate_second_case(cns)
 
-        cns = "".join(cns)
+        cns = ''.join(cns)
 
         return self.mask(cns) if mask else cns
 
     def mask(self, doc: str = '') -> str:
         """Coloca a máscara de CPF na variável doc."""
-        return "{} {} {} {}".format(doc[:3], doc[3:7], doc[7:11], doc[-4:])
+        return f"{doc[:3]} {doc[3:7]} {doc[7:11]} {doc[-4:]}"
 
     def _generate_first_case(self, cns: list, generate_random=False) -> list:
         """Gera um CNS válido para os casos que se inicia com 1 ou 2."""
@@ -95,7 +96,8 @@ def _generate_second_case(self, cns: list) -> list:
         return self._change_cns(cns, 15 - diff, diff)
 
     def _change_cns(self, cns: list, i: int, val: int) -> list:
-        """Altera o CNS recursivamente para que atenda as especificações de validade dele."""
+        """Altera o CNS recursivamente para que atenda as especificações de
+        validade dele."""
         if val == 0:
             if self._check_cns_valid(cns):
                 return cns
@@ -108,7 +110,7 @@ def _change_cns(self, cns: list, i: int, val: int) -> list:
             i += 1
             return self._change_cns(cns, i, val)
 
-        if not cns[i] == '9':
+        if cns[i] != '9':
             cns[i] = str(int(cns[i]) + 1)
             val -= (15 - i)
         else:
diff --git a/validate_docbr/CPF.py b/validate_docbr/CPF.py
index 9ce8e22..152137f 100644
--- a/validate_docbr/CPF.py
+++ b/validate_docbr/CPF.py
@@ -1,6 +1,7 @@
+from random import sample
 from typing import List
+
 from .BaseDoc import BaseDoc
-from random import sample
 
 
 class CPF(BaseDoc):
@@ -41,7 +42,7 @@ def generate(self, mask: bool = False) -> str:
 
     def mask(self, doc: str = '') -> str:
         """Coloca a máscara de CPF na variável doc."""
-        return "{}.{}.{}-{}".format(doc[:3], doc[3:6], doc[6:9], doc[-2:])
+        return f"{doc[:3]}.{doc[3:6]}.{doc[6:9]}-{doc[-2:]}"
 
     def _generate_first_digit(self, doc: list) -> str:
         """Gerar o primeiro dígito verificador do CPF."""
diff --git a/validate_docbr/Certidao.py b/validate_docbr/Certidao.py
index f64c7e2..296f21d 100644
--- a/validate_docbr/Certidao.py
+++ b/validate_docbr/Certidao.py
@@ -1,6 +1,7 @@
-from .BaseDoc import BaseDoc
 from random import sample
 
+from .BaseDoc import BaseDoc
+
 
 class Certidao(BaseDoc):
     """Classe referente a Certidão de Nascimento/Casamento/Óbito."""
diff --git a/validate_docbr/PIS.py b/validate_docbr/PIS.py
index d896ba1..3c17ea4 100644
--- a/validate_docbr/PIS.py
+++ b/validate_docbr/PIS.py
@@ -1,7 +1,8 @@
-from .BaseDoc import BaseDoc
 from random import sample
 from typing import Union
 
+from .BaseDoc import BaseDoc
+
 
 class PIS(BaseDoc):
     """Classe referente ao PIS/NIS/PASEP/NIT."""
@@ -33,7 +34,7 @@ def generate(self, mask: bool = False) -> str:
 
     def mask(self, doc: str = '') -> str:
         """Coloca a máscara de PIS/NIS/PASEP/NIT na variável doc."""
-        return "{}.{}.{}-{}".format(doc[:3], doc[3:8], doc[8:10], doc[10:])
+        return f"{doc[:3]}.{doc[3:8]}.{doc[8:10]}-{doc[10:]}"
 
     def _generate_digit(self, doc: Union[str, list]) -> str:
         """Gerar o dígito verificador do PIS/NIS/PASEP/NIT."""
diff --git a/validate_docbr/RENAVAM.py b/validate_docbr/RENAVAM.py
index cc6726e..805cb32 100644
--- a/validate_docbr/RENAVAM.py
+++ b/validate_docbr/RENAVAM.py
@@ -1,7 +1,8 @@
-from .BaseDoc import BaseDoc
 from random import sample
 from typing import Union
 
+from .BaseDoc import BaseDoc
+
 
 class RENAVAM(BaseDoc):
     """Classe referente ao Registro Nacional de Veículos Automotores (RENAVAM)."""
@@ -33,7 +34,7 @@ def generate(self, mask: bool = False) -> str:
 
     def mask(self, doc: str = '') -> str:
         """Coloca a máscara de Renavam na variável doc."""
-        return "{}-{}".format(doc[:10], doc[10])
+        return f"{doc[:10]}-{doc[10]}"
 
     def _generate_last_digit(self, doc: Union[str, list]) -> str:
         """Gerar o dígito verificador do Renavam."""
diff --git a/validate_docbr/TituloEleitoral.py b/validate_docbr/TituloEleitoral.py
index f7b26c4..78f187a 100644
--- a/validate_docbr/TituloEleitoral.py
+++ b/validate_docbr/TituloEleitoral.py
@@ -1,7 +1,8 @@
-from .BaseDoc import BaseDoc
 from random import sample
 from typing import List
 
+from .BaseDoc import BaseDoc
+
 
 class TituloEleitoral(BaseDoc):
     """Classe referente ao Título eleitoral"""
@@ -24,9 +25,13 @@ def validate(self, doc: str = '') -> bool:
             return False
 
         first_check_digit = self._compute_first_check_digit(doc_digits=doc_digits)
-        second_check_digit = self._compute_second_check_digit(doc_digits=doc_digits, first_check_digit=first_check_digit)
+        second_check_digit = self._compute_second_check_digit(
+            doc_digits=doc_digits,
+            first_check_digit=first_check_digit
+        )
 
-        return first_check_digit == doc_digits[-2] and second_check_digit == doc_digits[-1]
+        return first_check_digit == doc_digits[-2] \
+            and second_check_digit == doc_digits[-1]
 
     def generate(self, mask: bool = False) -> str:
         """Método para gerar um título eleitoral válido."""
@@ -36,8 +41,10 @@ def generate(self, mask: bool = False) -> str:
         document_digits.extend(map(int, state_identifier))
 
         first_check_digit = self._compute_first_check_digit(doc_digits=document_digits)
-        second_check_digit = self._compute_second_check_digit(doc_digits=document_digits,
-                                                               first_check_digit=first_check_digit)
+        second_check_digit = self._compute_second_check_digit(
+            doc_digits=document_digits,
+            first_check_digit=first_check_digit
+        )
         document_digits.extend([first_check_digit, second_check_digit])
 
         document = ''.join(map(str, document_digits))
@@ -49,14 +56,17 @@ def generate(self, mask: bool = False) -> str:
 
     def mask(self, doc: str = '') -> str:
         """Mascara o documento enviado"""
-        return '{} {} {}'.format(doc[0:4], doc[4:8], doc[8:])
+        return f'{doc[0:4]} {doc[4:8]} {doc[8:]}'
 
     def _compute_first_check_digit(self, doc_digits: List[int]) -> int:
         """Método que calcula o primeiro dígito verificador."""
         doc_digits_to_consider = doc_digits[self.first_check_digit_doc_slice]
         terms = [
             doc_digit * multiplier
-            for doc_digit, multiplier in zip(doc_digits_to_consider, self.first_check_digit_weights)
+            for doc_digit, multiplier in zip(
+                doc_digits_to_consider,
+                self.first_check_digit_weights
+            )
         ]
 
         total = sum(terms)
@@ -66,12 +76,20 @@ def _compute_first_check_digit(self, doc_digits: List[int]) -> int:
 
         return total % 11
 
-    def _compute_second_check_digit(self, doc_digits: List[int], first_check_digit: int) -> int:
+    def _compute_second_check_digit(
+            self,
+            doc_digits: List[int],
+            first_check_digit: int
+    ) -> int:
         """Método que calcula o segundo dígito verificador."""
-        doc_digits_to_consider = doc_digits[self.second_check_digit_doc_slice] + [first_check_digit]
+        doc_digits_to_consider = doc_digits[self.second_check_digit_doc_slice] \
+                                + [first_check_digit]
         terms = [
             doc_digit * multiplier
-            for doc_digit, multiplier in zip(doc_digits_to_consider, self.second_check_digit_weights)
+            for doc_digit, multiplier in zip(
+                doc_digits_to_consider,
+                self.second_check_digit_weights
+            )
         ]
 
         total = sum(terms)
diff --git a/validate_docbr/__init__.py b/validate_docbr/__init__.py
index 4919f0b..ac18fed 100644
--- a/validate_docbr/__init__.py
+++ b/validate_docbr/__init__.py
@@ -1,10 +1,23 @@
 from .BaseDoc import BaseDoc
-from .CPF import CPF
-from .CNPJ import CNPJ
+from .Certidao import Certidao
 from .CNH import CNH
+from .CNPJ import CNPJ
 from .CNS import CNS
+from .CPF import CPF
+from .generic import validate_docs
 from .PIS import PIS
-from .TituloEleitoral import TituloEleitoral
-from .Certidao import Certidao
 from .RENAVAM import RENAVAM
-from .generic import validate_docs
+from .TituloEleitoral import TituloEleitoral
+
+__all__ = [
+    'BaseDoc',
+    'CPF',
+    'CNPJ',
+    'CNH',
+    'CNS',
+    'PIS',
+    'TituloEleitoral',
+    'Certidao',
+    'RENAVAM',
+    'validate_docs',
+]
diff --git a/validate_docbr/generic.py b/validate_docbr/generic.py
index b883b19..9dd71a7 100644
--- a/validate_docbr/generic.py
+++ b/validate_docbr/generic.py
@@ -1,5 +1,6 @@
 import inspect
 from typing import List, Tuple, Type
+
 from .BaseDoc import BaseDoc