diff --git a/.github/workflows/publish-to-pypi.yml b/.github/workflows/publish-to-pypi.yaml
similarity index 100%
rename from .github/workflows/publish-to-pypi.yml
rename to .github/workflows/publish-to-pypi.yaml
diff --git a/CHAGELOG.md b/CHAGELOG.md
index 5a50090..c3d17be 100644
--- a/CHAGELOG.md
+++ b/CHAGELOG.md
@@ -3,43 +3,46 @@
 All notable changes to this project will be documented in this file.
 
 
-## [0.0.7] - 2025-01-14
+# [0.0.7] - 2025-01-14
 
-### Added
+## Added
 
 - Workflow to run tests on all supported python versions. [Check it out](.github/workflows/test_env.yaml)
 - Added more test coverage for validators and filters.
-- Added tracking of coverage in tests.
+- Added tracking of coverage in tests. [Check it out](https://coveralls.io/github/LeanderCS/flask-inputfilter)
+- New functionality for global filters and validators in InputFilters.
+- New functionality to define custom supported methods.
 
-### Changed
+### Validator
 
-- Updated root README.md to include badges.
+- New `NotInArrayValidator` to check if a value is not in a list. [Check it out](flask_inputfilter/Validator/NotInArrayValidator.py)
+- New `NotValidator` to invert the result of another validator. [Check it out](flask_inputfilter/Validator/NotValidator.py)
 
 
-## [0.0.6] - 2025-01-12
+# [0.0.6] - 2025-01-12
 
-### Added
+## Added
 
 - New date validators and filters.
 
-### Changed
+## Removed
 
 - Dropped support for Python 3.6.
 
 
-## [0.0.5] - 2025-01-12
+# [0.0.5] - 2025-01-12
 
-### Added
+## Added
 
 - New condition functionality between fields. [Check it out](flask_inputfilter/Condition/README.md)
 
-### Changed
+## Changed
 
 - Switched external_api config from dict to class. [Check it out](flask_inputfilter/Model/ExternalApiConfig.py)
 
 
-## [0.0.4] - 2025-01-09
+# [0.0.4] - 2025-01-09
 
-### Added
+## Added
 
 - New external api functionality. [Check it out](EXTERNAL_API.md)
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..6a10d35
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,9 @@
+# Contributing
+
+Thank you for considering contributing to the project. To make the process as easy and as effective as possible,
+please follow the guidelines below.
+
+## Reporting Issues
+
+If you find a bug or have a feature request, please open an issue on the project's GitHub repository.
+Before submitting an issue, please search the existing issues to see if your issue has already been reported.
diff --git a/README.rst b/README.rst
index fddbfe1..5234e91 100644
--- a/README.rst
+++ b/README.rst
@@ -118,11 +118,11 @@ Options
 The `add` method supports several options:
 
 - `Required`_
-- `Filter` (see `Filter` documentation in :file:`flask_inputfilter/Filter/README.md`)
-- `Validator` (see `Validator` documentation in :file:`flask_inputfilter/Validator/README.md`)
+- `Filter <flask_inputfilter/Filter/README.md>`_
+- `Validator <flask_inputfilter/Validator/README.md>`_
 - `Default`_
 - `Fallback`_
-- `ExternalApi` (see :file:`EXTERNAL_API.md`)
+- `ExternalApi <EXTERNAL_API.md>`_
 
 Required
 --------
diff --git a/flask_inputfilter/Condition/README.md b/flask_inputfilter/Condition/README.md
index 16aa7e3..86911c5 100644
--- a/flask_inputfilter/Condition/README.md
+++ b/flask_inputfilter/Condition/README.md
@@ -40,18 +40,20 @@ class TestInputFilter(InputFilter):
 
 The following conditions are available in the `Condition` module:
 
-1. [`CustomCondition`](CustomCondition.py) - A custom condition that can be used to validate the input data.
-2. [`EqualCondition`](EqualCondition.py) - Validates that the input is equal to the given value.
-3. [`ExactlyNOfCondition`](ExactlyNOfCondition.py) - Validates that exactly `n` of the given conditions are true.
-4. [`ExactlyNOfMatchesCondition`](ExactlyNOfMatchesCondition.py) - Validates that exactly `n` of the given matches are true.
-5. [`ExactlyOneOfCondition`](ExactlyOneOfCondition.py) - Validates that exactly one of the given conditions is true.
-6. [`ExactlyOneOfMatchesCondition`](ExactlyOneOfMatchesCondition.py) - Validates that exactly one of the given matches is true.
-7. [`IntegerBiggerThanCondition`](IntegerBiggerThanCondition.py) - Validates that the integer is bigger than the given value.
-8. [`NOfCondition`](NOfCondition.py) - Validates that at least `n` of the given conditions are true.
-9. [`NOfMatchesCondition`](NOfMatchesCondition.py) - Validates that at least `n` of the given matches are true.
-10. [`NotEqualCondition`](NotEqualCondition.py) - Validates that the input is not equal to the given value.
-11. [`OneOfCondition`](OneOfCondition.py) - Validates that at least one of the given conditions is true.
-12. [`OneOfMatchesCondition`](OneOfMatchesCondition.py) - Validates that at least one of the given matches is true.
-13. [`RequiredIfCondition`](RequiredIfCondition.py) - Validates that the input is required if the given condition is true.
-14. [`StringLongerThanCondition`](StringLongerThanCondition.py) - Validates that the string is longer than the given value.
-15. [`TemporalOrderCondition`](TemporalOrderCondition.py) - Validates that the input is in correct temporal order.
+1. [`ArrayLengthEqualCondition`](ArrayLengthEqualCondition.py) - Validates that the length of the array is equal to the given value.
+2. [`ArrayLongerThanCondition`](ArrayLongerThanCondition.py) - Validates that the length of the array is longer than the given value.
+3. [`CustomCondition`](CustomCondition.py) - A custom condition that can be used to validate the input data.
+4. [`EqualCondition`](EqualCondition.py) - Validates that the input is equal to the given value.
+5. [`ExactlyNOfCondition`](ExactlyNOfCondition.py) - Validates that exactly `n` of the given conditions are true.
+6. [`ExactlyNOfMatchesCondition`](ExactlyNOfMatchesCondition.py) - Validates that exactly `n` of the given matches are true.
+7. [`ExactlyOneOfCondition`](ExactlyOneOfCondition.py) - Validates that exactly one of the given conditions is true.
+8. [`ExactlyOneOfMatchesCondition`](ExactlyOneOfMatchesCondition.py) - Validates that exactly one of the given matches is true.
+9. [`IntegerBiggerThanCondition`](IntegerBiggerThanCondition.py) - Validates that the integer is bigger than the given value.
+10. [`NOfCondition`](NOfCondition.py) - Validates that at least `n` of the given conditions are true.
+11. [`NOfMatchesCondition`](NOfMatchesCondition.py) - Validates that at least `n` of the given matches are true.
+12. [`NotEqualCondition`](NotEqualCondition.py) - Validates that the input is not equal to the given value.
+13. [`OneOfCondition`](OneOfCondition.py) - Validates that at least one of the given conditions is true.
+14. [`OneOfMatchesCondition`](OneOfMatchesCondition.py) - Validates that at least one of the given matches is true.
+15. [`RequiredIfCondition`](RequiredIfCondition.py) - Validates that the input is required if the given field has a specific value.
+16. [`StringLongerThanCondition`](StringLongerThanCondition.py) - Validates that the string is longer than the given value.
+17. [`TemporalOrderCondition`](TemporalOrderCondition.py) - Validates that the input is in correct temporal order.
diff --git a/flask_inputfilter/Condition/RequiredIfCondition.py b/flask_inputfilter/Condition/RequiredIfCondition.py
index 650d969..c04a299 100644
--- a/flask_inputfilter/Condition/RequiredIfCondition.py
+++ b/flask_inputfilter/Condition/RequiredIfCondition.py
@@ -1,4 +1,4 @@
-from typing import Any, Dict
+from typing import Any, Dict, List, Optional, Union
 
 from .BaseCondition import BaseCondition
 
@@ -10,14 +10,28 @@ class RequiredIfCondition(BaseCondition):
     """
 
     def __init__(
-        self, condition_field: str, value: Any, required_field: str
+        self,
+        condition_field: str,
+        value: Optional[Union[Any, List[Any]]],
+        required_field: str,
     ) -> None:
         self.condition_field = condition_field
         self.value = value
         self.required_field = required_field
 
     def check(self, data: Dict[str, Any]) -> bool:
-        return (
-            data.get(self.condition_field) != self.value
-            or data.get(self.required_field) is not None
-        )
+        condition_value = data.get(self.condition_field)
+
+        if self.value is not None:
+            if isinstance(self.value, list):
+                if condition_value in self.value:
+                    return data.get(self.required_field) is not None
+            else:
+                if condition_value == self.value:
+                    return data.get(self.required_field) is not None
+
+        else:
+            if condition_value is not None:
+                return data.get(self.required_field) is not None
+
+        return True
diff --git a/flask_inputfilter/Filter/README.md b/flask_inputfilter/Filter/README.md
index 80b8a10..5cd0862 100644
--- a/flask_inputfilter/Filter/README.md
+++ b/flask_inputfilter/Filter/README.md
@@ -7,23 +7,26 @@ The `Filter` module contains the filters that can be used to filter the input da
 The following filters are available in the `Filter` module:
 
 1. [`ArrayExplodeFilter`](ArrayExplodeFilter.py) - Explodes the input string into an array.
-2. [`RemoveEmojisFilter`](RemoveEmojisFilter.py) - Removes the emojis from the string.
-3. [`SlugifyFilter`](SlugifyFilter.py) - Converts the string to a slug.
-4. [`StringTrimFilter`](StringTrimFilter.py) - Trims the whitespace from the beginning and end of the string.
-5. [`ToAlphaNumericFilter`](ToAlphaNumericFilter.py) - Converts the string to an alphanumeric string.
-6. [`ToBooleanFilter`](ToBooleanFilter.py) - Converts the string to a boolean value.
-7. [`ToCamelCaseFilter`](ToCamelCaseFilter.py) - Converts the string to camel case.
-8. [`ToDateFilter`](ToDateFilter.py) - Converts a string to a date value.
-9. [`ToDateTimeFilter`](ToDateTimeFilter.py) - Converts a string to a datetime value.
-10. [`ToEnumFilter`](ToEnumFilter.py) - Converts a string or integer to an enum value.
-11. [`ToFloatFilter`](ToFloatFilter.py) - Converts a string to a float value.
-12. [`ToIntegerFilter`](ToIntegerFilter.py) - Converts a string to an integer value.
-13. [`ToIsoFilter`](ToIsoFilter.py) - Converts a string to an ISO8601 date time value.
-14. [`ToLowerFilter`](ToLowerFilter.py) - Converts a string to lowercase.
-15. [`ToNormalizedUnicodeFilter`](ToNormalizedUnicodeFilter.py) - Normalizes a unicode string.
-16. [`ToNullFilter`](ToNullFilter.py) - Converts the string to `None` if it is already `None` or `''` (empty string).
-17. [`ToPascaleCaseFilter`](ToPascaleCaseFilter.py) - Converts the string to pascal case.
-18. [`ToSnakeCaseFilter`](ToSnakeCaseFilter.py) - Converts the string to snake case.
-19. [`ToStringFilter`](ToStringFilter.py) - Converts the input to a string value.
-20. [`ToUpperFilter`](ToUpperFilter.py) - Converts the string to uppercase.
-21. [`WhitespaceCollapseFilter`](WhitespaceCollapseFilter.py) - Collapses the whitespace in the string.
+2. [`BlacklistFilter`](BlacklistFilter.py) - Filters the string based on the blacklist.
+3. [`RemoveEmojisFilter`](RemoveEmojisFilter.py) - Removes the emojis from the string.
+4. [`SlugifyFilter`](SlugifyFilter.py) - Converts the string to a slug.
+5. [`StringTrimFilter`](StringTrimFilter.py) - Trims the whitespace from the beginning and end of the string.
+6. [`ToAlphaNumericFilter`](ToAlphaNumericFilter.py) - Converts the string to an alphanumeric string.
+7. [`ToBooleanFilter`](ToBooleanFilter.py) - Converts the string to a boolean value.
+8. [`ToCamelCaseFilter`](ToCamelCaseFilter.py) - Converts the string to camel case.
+9. [`ToDateFilter`](ToDateFilter.py) - Converts a string to a date value.
+10. [`ToDateTimeFilter`](ToDateTimeFilter.py) - Converts a string to a datetime value.
+11. [`ToEnumFilter`](ToEnumFilter.py) - Converts a string or integer to an enum value.
+12. [`ToFloatFilter`](ToFloatFilter.py) - Converts a string to a float value.
+13. [`ToIntegerFilter`](ToIntegerFilter.py) - Converts a string to an integer value.
+14. [`ToIsoFilter`](ToIsoFilter.py) - Converts a string to an ISO8601 date time value.
+15. [`ToLowerFilter`](ToLowerFilter.py) - Converts a string to lowercase.
+16. [`ToNormalizedUnicodeFilter`](ToNormalizedUnicodeFilter.py) - Normalizes a unicode string.
+17. [`ToNullFilter`](ToNullFilter.py) - Converts the string to `None` if it is already `None` or `''` (empty string).
+18. [`ToPascaleCaseFilter`](ToPascaleCaseFilter.py) - Converts the string to pascal case.
+19. [`ToSnakeCaseFilter`](ToSnakeCaseFilter.py) - Converts the string to snake case.
+20. [`ToStringFilter`](ToStringFilter.py) - Converts the input to a string value.
+21. [`ToUpperFilter`](ToUpperFilter.py) - Converts the string to uppercase.
+22. [`TruncateFilter`](TruncateFilter.py) - Truncates the string to the specified length.
+23. [`WhitelistFilter`](WhitelistFilter.py) - Filters the string based on the whitelist.
+24. [`WhitespaceCollapseFilter`](WhitespaceCollapseFilter.py) - Collapses the whitespace in the string.
diff --git a/flask_inputfilter/InputFilter.py b/flask_inputfilter/InputFilter.py
index 5c04c3a..4e75498 100644
--- a/flask_inputfilter/InputFilter.py
+++ b/flask_inputfilter/InputFilter.py
@@ -16,9 +16,12 @@ class InputFilter:
     Base class for input filters.
     """
 
-    def __init__(self) -> None:
+    def __init__(self, methods: Optional[List[str]] = None) -> None:
+        self.methods = methods or ["GET", "POST", "PATCH", "PUT", "DELETE"]
         self.fields = {}
         self.conditions = []
+        self.global_filters = []
+        self.global_validators = []
 
     def add(
         self,
@@ -36,7 +39,8 @@ def add(
         :param name: The name of the field.
         :param required: Whether the field is required.
         :param default: The default value of the field.
-        :param fallback: The fallback value of the field.
+        :param fallback: The fallback value of the field, if validations fails
+        or field None, although it is required .
         :param filters: The filters to apply to the field value.
         :param validators: The validators to apply to the field value.
         :param external_api: Configuration for an external API call.
@@ -57,15 +61,27 @@ def addCondition(self, condition: BaseCondition) -> None:
         """
         self.conditions.append(condition)
 
+    def addGlobalFilter(self, filter_: BaseFilter) -> None:
+        """
+        Add a global filter to be applied to all fields.
+        """
+        self.global_filters.append(filter_)
+
+    def addGlobalValidator(self, validator: BaseValidator) -> None:
+        """
+        Add a global validator to be applied to all fields.
+        """
+        self.global_validators.append(validator)
+
     def _applyFilters(self, field_name: str, value: Any) -> Any:
         """
         Apply filters to the field value.
         """
 
-        field = self.fields.get(field_name)
+        for filter_ in self.global_filters:
+            value = filter_.apply(value)
 
-        if not field:
-            return value
+        field = self.fields.get(field_name)
 
         for filter_ in field["filters"]:
             value = filter_.apply(value)
@@ -77,10 +93,10 @@ def _validateField(self, field_name: str, value: Any) -> None:
         Validate the field value.
         """
 
-        field = self.fields.get(field_name)
+        for validator in self.global_validators:
+            validator.validate(value)
 
-        if not field:
-            return
+        field = self.fields.get(field_name)
 
         for validator in field["validators"]:
             validator.validate(value)
@@ -133,38 +149,31 @@ def _callExternalApi(
         return result
 
     @staticmethod
-    def __replacePlaceholders(url: str, validated_data: dict) -> str:
+    def __replacePlaceholders(value: str, validated_data: dict) -> str:
         """
-        Ersetzt alle Platzhalter in der URL, die mit {{}} definiert sind,
-        durch die entsprechenden Werte aus den Parametern.
+        Replace all placeholders, marked with '{{ }}' in value
+        with the corresponding values from validated_data.
         """
 
         return re.sub(
             r"{{(.*?)}}",
             lambda match: str(validated_data.get(match.group(1))),
-            url,
+            value,
         )
 
-    @staticmethod
     def __replacePlaceholdersInParams(
-        params: dict, validated_data: dict
+        self, params: dict, validated_data: dict
     ) -> dict:
         """
         Replace all placeholders in params with the
         corresponding values from validated_data.
         """
-        replaced_params = {}
-        for key, value in params.items():
-            if isinstance(value, str):
-                replaced_value = re.sub(
-                    r"{{(.*?)}}",
-                    lambda match: str(validated_data.get(match.group(1), "")),
-                    value,
-                )
-                replaced_params[key] = replaced_value
-            else:
-                replaced_params[key] = value
-        return replaced_params
+        return {
+            key: self.__replacePlaceholders(value, validated_data)
+            if isinstance(value, str)
+            else value
+            for key, value in params.items()
+        }
 
     def validateData(
         self, data: Dict[str, Any], kwargs: Dict[str, Any] = None
@@ -221,7 +230,7 @@ def validateData(
                         external_api_config, validated_data
                     )
 
-                except ValidationError:
+                except Exception:
                     if field_info.get("fallback") is None:
                         raise ValidationError(
                             f"External API call failed for field "
@@ -274,25 +283,13 @@ def decorator(
             def wrapper(
                 *args, **kwargs
             ) -> Union[Response, Tuple[Any, Dict[str, Any]]]:
-                if request.method == "GET":
-                    data = request.args
-
-                elif request.method in ["POST", "PUT", "DELETE"]:
-                    if not request.is_json:
-                        data = request.args
-
-                    else:
-                        data = request.json
-
-                else:
-                    return Response(
-                        status=415, response="Unsupported method Type"
-                    )
+                if request.method not in cls().methods:
+                    return Response(status=405, response="Method Not Allowed")
 
-                inputFilter = cls()
+                data = request.json if request.is_json else request.args
 
                 try:
-                    g.validated_data = inputFilter.validateData(data, kwargs)
+                    g.validated_data = cls().validateData(data, kwargs)
 
                 except ValidationError as e:
                     return Response(status=400, response=str(e))
diff --git a/flask_inputfilter/Validator/ArrayElementValidator.py b/flask_inputfilter/Validator/ArrayElementValidator.py
index d430b0b..e4d75be 100644
--- a/flask_inputfilter/Validator/ArrayElementValidator.py
+++ b/flask_inputfilter/Validator/ArrayElementValidator.py
@@ -1,4 +1,4 @@
-from typing import TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -15,14 +15,14 @@ class ArrayElementValidator(BaseValidator):
     def __init__(
         self,
         elementFilter: "InputFilter",
-        error_message: str = "Value '{}' is not in '{}'",
+        error_message: Optional[str] = None,
     ) -> None:
         self.elementFilter = elementFilter
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, list):
-            raise ValidationError("Value is not an array")
+            raise ValidationError(f"Value '{value}' is not an array")
 
         for i, element in enumerate(value):
             try:
@@ -30,9 +30,7 @@ def validate(self, value: Any) -> None:
                 value[i] = validated_element
 
             except ValidationError:
-                if "{}" in self.error_message:
-                    raise ValidationError(
-                        self.error_message.format(element, self.elementFilter)
-                    )
-
-                raise ValidationError(self.error_message)
+                raise ValidationError(
+                    self.error_message
+                    or f"Value '{element}' is not in '{self.elementFilter}'"
+                )
diff --git a/flask_inputfilter/Validator/ArrayLengthValidator.py b/flask_inputfilter/Validator/ArrayLengthValidator.py
index cf8b281..06fdebd 100644
--- a/flask_inputfilter/Validator/ArrayLengthValidator.py
+++ b/flask_inputfilter/Validator/ArrayLengthValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -14,7 +14,7 @@ def __init__(
         self,
         min_length: int = 0,
         max_length: int = float("inf"),
-        error_message: str = "Array length must be between {} and {}.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.min_length = min_length
         self.max_length = max_length
@@ -22,14 +22,13 @@ def __init__(
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, list):
-            raise ValidationError("Value must be a list.")
+            raise ValidationError(f"Value '{value}' must be a list.")
 
         array_length = len(value)
 
         if not (self.min_length <= array_length <= self.max_length):
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(self.min_length, self.max_length)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Array length must be between '{self.min_length}' "
+                f"and '{self.max_length}'."
+            )
diff --git a/flask_inputfilter/Validator/DateAfterValidator.py b/flask_inputfilter/Validator/DateAfterValidator.py
index 54b1055..3acb0da 100644
--- a/flask_inputfilter/Validator/DateAfterValidator.py
+++ b/flask_inputfilter/Validator/DateAfterValidator.py
@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Any, Union
+from typing import Any, Optional, Union
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -14,7 +14,7 @@ class DateAfterValidator(BaseValidator):
     def __init__(
         self,
         reference_date: Union[str, date, datetime],
-        error_message: str = "Date '{}' is not after '{}'.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.reference_date = reference_date
         self.error_message = error_message
@@ -24,12 +24,10 @@ def validate(self, value: Any) -> None:
         value_datetime = self._parse_date(value)
 
         if value_datetime <= value_reference_date:
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(value, value_reference_date)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Date '{value}' is not after '{value_reference_date}'."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         if isinstance(value, datetime):
@@ -43,9 +41,9 @@ def _parse_date(self, value: Any) -> datetime:
                 return datetime.fromisoformat(value)
 
             except ValueError:
-                raise ValidationError(f"Invalid ISO 8601 format: {value}")
+                raise ValidationError(f"Invalid ISO 8601 format '{value}'.")
 
         else:
             raise ValidationError(
-                f"Unsupported type for date comparison: {type(value)}"
+                f"Unsupported type for date comparison '{type(value)}'."
             )
diff --git a/flask_inputfilter/Validator/DateBeforeValidator.py b/flask_inputfilter/Validator/DateBeforeValidator.py
index dda4fd9..e8088ec 100644
--- a/flask_inputfilter/Validator/DateBeforeValidator.py
+++ b/flask_inputfilter/Validator/DateBeforeValidator.py
@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Any, Union
+from typing import Any, Optional, Union
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -14,7 +14,7 @@ class DateBeforeValidator(BaseValidator):
     def __init__(
         self,
         reference_date: Union[str, date, datetime],
-        error_message: str = "Date '{}' is not before '{}'.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.reference_date = reference_date
         self.error_message = error_message
@@ -24,12 +24,10 @@ def validate(self, value: Any) -> None:
         value_datetime = self._parse_date(value)
 
         if value_datetime >= value_reference_date:
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(value, value_reference_date)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Date '{value}' is not before '{value_reference_date}'."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         if isinstance(value, datetime):
@@ -43,9 +41,9 @@ def _parse_date(self, value: Any) -> datetime:
                 return datetime.fromisoformat(value)
 
             except ValueError:
-                raise ValidationError(f"Invalid ISO 8601 format: {value}")
+                raise ValidationError(f"Invalid ISO 8601 format '{value}'.")
 
         else:
             raise ValidationError(
-                f"Unsupported type for date comparison: {type(value)}"
+                f"Unsupported type for date comparison '{type(value)}'."
             )
diff --git a/flask_inputfilter/Validator/DateRangeValidator.py b/flask_inputfilter/Validator/DateRangeValidator.py
index 4a0b550..2308712 100644
--- a/flask_inputfilter/Validator/DateRangeValidator.py
+++ b/flask_inputfilter/Validator/DateRangeValidator.py
@@ -14,7 +14,7 @@ def __init__(
         self,
         min_date: Optional[Union[str, date, datetime]] = None,
         max_date: Optional[Union[str, date, datetime]] = None,
-        error_message="Date '{}' is not in the range from '{}' to '{}'.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.min_date = min_date
         self.max_date = max_date
@@ -28,14 +28,11 @@ def validate(self, value: Any) -> None:
         if (min_date and value_date < min_date) or (
             max_date and value_date > max_date
         ):
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(
-                        value, self.min_date, self.max_date
-                    )
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Date '{value}' is not in the range from "
+                f"'{self.min_date}' to '{self.max_date}'."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         """
@@ -51,11 +48,11 @@ def _parse_date(self, value: Any) -> datetime:
                 return datetime.fromisoformat(value)
 
             except ValueError:
-                raise ValidationError(f"Invalid ISO 8601 format: {value}")
+                raise ValidationError(f"Invalid ISO 8601 format '{value}'.")
 
         elif isinstance(value, date):
             return datetime.combine(value, datetime.min.time())
 
         raise ValidationError(
-            f"Unsupported type for past date validation: {type(value)}"
+            f"Unsupported type for past date validation '{type(value)}'."
         )
diff --git a/flask_inputfilter/Validator/FloatPrecisionValidator.py b/flask_inputfilter/Validator/FloatPrecisionValidator.py
index 05dc6ab..867afa5 100644
--- a/flask_inputfilter/Validator/FloatPrecisionValidator.py
+++ b/flask_inputfilter/Validator/FloatPrecisionValidator.py
@@ -1,5 +1,5 @@
 import re
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -14,8 +14,7 @@ def __init__(
         self,
         precision: int,
         scale: int,
-        error_message: str = "Value '{}' has more than {} digits in total or "
-        "{} digits after the decimal point.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.precision = precision
         self.scale = scale
@@ -23,23 +22,23 @@ def __init__(
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, (float, int)):
-            raise ValidationError("Value must be a float or an integer")
+            raise ValidationError(
+                f"Value '{value}' must be a float or an integer."
+            )
 
         value_str = str(value)
         match = re.match(r"^-?(\d+)(\.(\d+))?$", value_str)
         if not match:
-            raise ValidationError("Value is not a valid float")
+            raise ValidationError(f"Value '{value}' is not a valid float.")
 
         digits_before = len(match.group(1))
         digits_after = len(match.group(3)) if match.group(3) else 0
         total_digits = digits_before + digits_after
 
         if total_digits > self.precision or digits_after > self.scale:
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(
-                        value, self.precision, self.scale
-                    )
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' has more than {self.precision} digits "
+                f"in total or '{self.scale}' digits after the "
+                f"decimal point."
+            )
diff --git a/flask_inputfilter/Validator/InArrayValidator.py b/flask_inputfilter/Validator/InArrayValidator.py
index bf1cee3..9f3437f 100644
--- a/flask_inputfilter/Validator/InArrayValidator.py
+++ b/flask_inputfilter/Validator/InArrayValidator.py
@@ -1,4 +1,4 @@
-from typing import Any, List
+from typing import Any, List, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -13,7 +13,7 @@ def __init__(
         self,
         haystack: List[Any],
         strict: bool = False,
-        error_message: str = "Value '{}' is not in the allowed values '{}'.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.haystack = haystack
         self.strict = strict
@@ -32,9 +32,8 @@ def validate(self, value: Any) -> None:
                     raise ValidationError
 
         except Exception:
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(value, self.haystack)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not in the allowed "
+                f"values '{self.haystack}'."
+            )
diff --git a/flask_inputfilter/Validator/InEnumValidator.py b/flask_inputfilter/Validator/InEnumValidator.py
index a6fba7a..cd71f04 100644
--- a/flask_inputfilter/Validator/InEnumValidator.py
+++ b/flask_inputfilter/Validator/InEnumValidator.py
@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Any, Type
+from typing import Any, Optional, Type
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -13,7 +13,7 @@ class InEnumValidator(BaseValidator):
     def __init__(
         self,
         enumClass: Type[Enum],
-        error_message: str = "Value '{}' is not an value of '{}'",
+        error_message: Optional[str] = None,
     ) -> None:
         self.enumClass = enumClass
         self.error_message = error_message
@@ -22,9 +22,7 @@ def validate(self, value: Any) -> None:
         if not any(
             value.lower() == item.name.lower() for item in self.enumClass
         ):
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(value, self.enumClass)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not an value of '{self.enumClass}'"
+            )
diff --git a/flask_inputfilter/Validator/IsArrayValidator.py b/flask_inputfilter/Validator/IsArrayValidator.py
index 5524131..47c47e6 100644
--- a/flask_inputfilter/Validator/IsArrayValidator.py
+++ b/flask_inputfilter/Validator/IsArrayValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -9,14 +9,11 @@ class IsArrayValidator(BaseValidator):
     Validator that checks if a value is an array.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not an array."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, list):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Value '{value}' is not an array."
+            )
diff --git a/flask_inputfilter/Validator/IsBase64ImageCorrectSizeValidator.py b/flask_inputfilter/Validator/IsBase64ImageCorrectSizeValidator.py
index 5a6f904..a95a725 100644
--- a/flask_inputfilter/Validator/IsBase64ImageCorrectSizeValidator.py
+++ b/flask_inputfilter/Validator/IsBase64ImageCorrectSizeValidator.py
@@ -1,5 +1,5 @@
 import base64
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -15,8 +15,7 @@ def __init__(
         self,
         minSize: int = 1,
         maxSize: int = 4 * 1024 * 1024,
-        error_message: str = "The image is invalid or does not "
-        "have an allowed size.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.min_size = minSize
         self.max_size = maxSize
@@ -30,4 +29,7 @@ def validate(self, value: Any) -> None:
                 raise ValidationError
 
         except Exception:
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or "The image is invalid or does not have an allowed size."
+            )
diff --git a/flask_inputfilter/Validator/IsBase64ImageValidator.py b/flask_inputfilter/Validator/IsBase64ImageValidator.py
index c89d642..41cbeaf 100644
--- a/flask_inputfilter/Validator/IsBase64ImageValidator.py
+++ b/flask_inputfilter/Validator/IsBase64ImageValidator.py
@@ -1,6 +1,6 @@
 import base64
 import io
-from typing import Any
+from typing import Any, Optional
 
 from PIL import Image
 
@@ -15,8 +15,7 @@ class IsBase64ImageValidator(BaseValidator):
 
     def __init__(
         self,
-        error_message: str = "The image is invalid or does not "
-        "have an allowed size.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.error_message = error_message
 
@@ -27,4 +26,7 @@ def validate(self, value: Any) -> None:
             image.verify()
 
         except Exception:
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or "The image is invalid or does not have an allowed size."
+            )
diff --git a/flask_inputfilter/Validator/IsBooleanValidator.py b/flask_inputfilter/Validator/IsBooleanValidator.py
index 3f87b53..7892ffd 100644
--- a/flask_inputfilter/Validator/IsBooleanValidator.py
+++ b/flask_inputfilter/Validator/IsBooleanValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -9,14 +9,11 @@ class IsBooleanValidator(BaseValidator):
     Validator that checks if a value is a bool.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not a bool."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, bool):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Value '{value}' is not a boolean."
+            )
diff --git a/flask_inputfilter/Validator/IsFloatValidator.py b/flask_inputfilter/Validator/IsFloatValidator.py
index 11fd99a..b769536 100644
--- a/flask_inputfilter/Validator/IsFloatValidator.py
+++ b/flask_inputfilter/Validator/IsFloatValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -9,14 +9,11 @@ class IsFloatValidator(BaseValidator):
     Validator that checks if a value is a float.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not a float."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, float):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Value '{value}' is not a float."
+            )
diff --git a/flask_inputfilter/Validator/IsFutureDateValidator.py b/flask_inputfilter/Validator/IsFutureDateValidator.py
index 30124da..f9e5bb5 100644
--- a/flask_inputfilter/Validator/IsFutureDateValidator.py
+++ b/flask_inputfilter/Validator/IsFutureDateValidator.py
@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -10,19 +10,16 @@ class IsFutureDateValidator(BaseValidator):
     Validator that checks if a date is in the future.
     """
 
-    def __init__(
-        self, error_message: str = "Date '{}' is not in the future."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         value_date = self._parse_date(value)
 
         if value_date <= datetime.now():
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Date '{value}' is not in the future."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         """
@@ -41,8 +38,8 @@ def _parse_date(self, value: Any) -> datetime:
                 return datetime.fromisoformat(value)
 
             except ValueError:
-                raise ValidationError(f"Invalid ISO 8601 format: {value}")
+                raise ValidationError(f"Invalid ISO 8601 format '{value}'.")
 
         raise ValidationError(
-            f"Unsupported type for past date validation: {type(value)}"
+            f"Unsupported type for past date validation '{type(value)}'."
         )
diff --git a/flask_inputfilter/Validator/IsHexadecimalValidator.py b/flask_inputfilter/Validator/IsHexadecimalValidator.py
index 9170469..ff0e1bd 100644
--- a/flask_inputfilter/Validator/IsHexadecimalValidator.py
+++ b/flask_inputfilter/Validator/IsHexadecimalValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -11,7 +11,7 @@ class IsHexadecimalValidator(BaseValidator):
 
     def __init__(
         self,
-        error_message: str = "Value '{}' is not a valid hexadecimal string.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.error_message = error_message
 
@@ -23,4 +23,7 @@ def validate(self, value: Any) -> None:
             int(value, 16)
 
         except ValueError:
-            raise ValidationError(self.error_message.format(value))
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not a valid hexadecimal string."
+            )
diff --git a/flask_inputfilter/Validator/IsInstanceValidator.py b/flask_inputfilter/Validator/IsInstanceValidator.py
index 78f4b7e..fbf2da4 100644
--- a/flask_inputfilter/Validator/IsInstanceValidator.py
+++ b/flask_inputfilter/Validator/IsInstanceValidator.py
@@ -1,4 +1,4 @@
-from typing import Any, Type
+from typing import Any, Optional, Type
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -12,16 +12,14 @@ class IsInstanceValidator(BaseValidator):
     def __init__(
         self,
         classType: Type[Any],
-        error_message: str = "Value '{}' is not an instance of '{}'.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.classType = classType
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, self.classType):
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(value, self.classType)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not an instance of '{self.classType}'."
+            )
diff --git a/flask_inputfilter/Validator/IsIntegerValidator.py b/flask_inputfilter/Validator/IsIntegerValidator.py
index d9d4f16..306066f 100644
--- a/flask_inputfilter/Validator/IsIntegerValidator.py
+++ b/flask_inputfilter/Validator/IsIntegerValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -9,14 +9,11 @@ class IsIntegerValidator(BaseValidator):
     Validator that checks if a value is an integer.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not an integer."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, int):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message, f"Value '{value}' is not an integer."
+            )
diff --git a/flask_inputfilter/Validator/IsJsonValidator.py b/flask_inputfilter/Validator/IsJsonValidator.py
index 12ecaec..76b6cd8 100644
--- a/flask_inputfilter/Validator/IsJsonValidator.py
+++ b/flask_inputfilter/Validator/IsJsonValidator.py
@@ -1,5 +1,5 @@
 import json
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -10,9 +10,7 @@ class IsJsonValidator(BaseValidator):
     Validator that checks if a value is a valid JSON string.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not a valid JSON string."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
@@ -20,7 +18,7 @@ def validate(self, value: Any) -> None:
             json.loads(value)
 
         except (TypeError, ValueError):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not a valid JSON string."
+            )
diff --git a/flask_inputfilter/Validator/IsPastDateValidator.py b/flask_inputfilter/Validator/IsPastDateValidator.py
index 700d43a..9ee4e49 100644
--- a/flask_inputfilter/Validator/IsPastDateValidator.py
+++ b/flask_inputfilter/Validator/IsPastDateValidator.py
@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -10,19 +10,16 @@ class IsPastDateValidator(BaseValidator):
     Validator that checks if a date is in the past.
     """
 
-    def __init__(
-        self, error_message: str = "Date '{}' is not in the past."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         value_datetime = self._parse_date(value)
 
         if value_datetime >= datetime.now():
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Date '{value}' is not in the past."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         """
@@ -38,12 +35,12 @@ def _parse_date(self, value: Any) -> datetime:
                 return datetime.fromisoformat(value)
 
             except ValueError:
-                raise ValidationError(f"Invalid ISO 8601 format: {value}")
+                raise ValidationError(f"Invalid ISO 8601 format '{value}'.")
 
         elif isinstance(value, date):
             return datetime.combine(value, datetime.min.time())
 
         else:
             raise ValidationError(
-                f"Unsupported type for past date validation: {type(value)}"
+                f"Unsupported type for past date validation '{type(value)}'."
             )
diff --git a/flask_inputfilter/Validator/IsStringValidator.py b/flask_inputfilter/Validator/IsStringValidator.py
index 3c775a0..813ae50 100644
--- a/flask_inputfilter/Validator/IsStringValidator.py
+++ b/flask_inputfilter/Validator/IsStringValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -9,14 +9,11 @@ class IsStringValidator(BaseValidator):
     Validator that checks if a value is a string.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not a string."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         if not isinstance(value, str):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Value '{value}' is not a string."
+            )
diff --git a/flask_inputfilter/Validator/IsUUIDValidator.py b/flask_inputfilter/Validator/IsUUIDValidator.py
index a212a14..51b8396 100644
--- a/flask_inputfilter/Validator/IsUUIDValidator.py
+++ b/flask_inputfilter/Validator/IsUUIDValidator.py
@@ -1,5 +1,5 @@
 import uuid
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -10,9 +10,7 @@ class IsUUIDValidator(BaseValidator):
     Validator that checks if a value is a valid UUID string.
     """
 
-    def __init__(
-        self, error_message: str = "Value '{}' is not a valid UUID."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
@@ -23,4 +21,6 @@ def validate(self, value: Any) -> None:
             uuid.UUID(value)
 
         except ValueError:
-            raise ValidationError(self.error_message.format(value))
+            raise ValidationError(
+                self.error_message or f"Value '{value}' is not a valid UUID."
+            )
diff --git a/flask_inputfilter/Validator/IsWeekdayValidator.py b/flask_inputfilter/Validator/IsWeekdayValidator.py
index 26a01dc..fd0e7ca 100644
--- a/flask_inputfilter/Validator/IsWeekdayValidator.py
+++ b/flask_inputfilter/Validator/IsWeekdayValidator.py
@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -11,19 +11,16 @@ class IsWeekdayValidator(BaseValidator):
     Supports datetime and ISO 8601 formatted strings.
     """
 
-    def __init__(
-        self, error_message: str = "Date '{}' is not a weekday."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         value_datetime = self._parse_date(value)
 
         if value_datetime.weekday() in (5, 6):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Date '{value}' is not a weekday."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         if isinstance(value, datetime):
@@ -37,9 +34,9 @@ def _parse_date(self, value: Any) -> datetime:
                 return datetime.fromisoformat(value)
 
             except ValueError:
-                raise ValidationError(f"Invalid ISO 8601 format: {value}")
+                raise ValidationError(f"Invalid ISO 8601 format '{value}'.")
 
         else:
             raise ValidationError(
-                f"Unsupported type for weekday validation: {type(value)}"
+                f"Unsupported type for weekday validation '{type(value)}'."
             )
diff --git a/flask_inputfilter/Validator/IsWeekendValidator.py b/flask_inputfilter/Validator/IsWeekendValidator.py
index 1162dfa..f9845e9 100644
--- a/flask_inputfilter/Validator/IsWeekendValidator.py
+++ b/flask_inputfilter/Validator/IsWeekendValidator.py
@@ -1,5 +1,5 @@
 from datetime import date, datetime
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -11,19 +11,16 @@ class IsWeekendValidator(BaseValidator):
     Supports datetime and ISO 8601 formatted strings.
     """
 
-    def __init__(
-        self, error_message: str = "Date '{}' is not on a weekend."
-    ) -> None:
+    def __init__(self, error_message: Optional[str] = None) -> None:
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
         value_datetime = self._parse_date(value)
 
         if value_datetime.weekday() not in (5, 6):
-            if "{}" in self.error_message:
-                raise ValidationError(self.error_message.format(value))
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message or f"Date '{value}' is not on a weekend."
+            )
 
     def _parse_date(self, value: Any) -> datetime:
         if isinstance(value, datetime):
diff --git a/flask_inputfilter/Validator/LengthValidator.py b/flask_inputfilter/Validator/LengthValidator.py
index b77eda8..8fc65a6 100644
--- a/flask_inputfilter/Validator/LengthValidator.py
+++ b/flask_inputfilter/Validator/LengthValidator.py
@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -11,7 +11,6 @@ class LengthEnum(Enum):
     """
 
     LEAST = "least"
-
     MOST = "most"
 
 
@@ -22,31 +21,20 @@ class LengthValidator(BaseValidator):
 
     def __init__(
         self,
-        min_length: int = 0,
-        max_length: int = None,
-        error_message: str = "Value '{}' must be at {} '{}' characters long.",
+        min_length: Optional[int] = None,
+        max_length: Optional[int] = None,
+        error_message: Optional[str] = None,
     ) -> None:
         self.min_length = min_length
         self.max_length = max_length
         self.error_message = error_message
 
     def validate(self, value: Any) -> None:
-        if len(value) < self.min_length:
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(
-                        value, LengthEnum.LEAST.value, self.min_length
-                    )
-                )
-
-            raise ValidationError(self.error_message)
-
-        if self.max_length is not None and len(value) > self.max_length:
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(
-                        value, LengthEnum.MOST.value, self.max_length
-                    )
-                )
-
-            raise ValidationError(self.error_message)
+        if (self.max_length is not None and len(value) < self.min_length) or (
+            self.max_length is not None and len(value) > self.max_length
+        ):
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not within the range of "
+                f"'{self.min_length}' to '{self.max_length}'."
+            )
diff --git a/flask_inputfilter/Validator/NotInArrayValidator.py b/flask_inputfilter/Validator/NotInArrayValidator.py
new file mode 100644
index 0000000..828e936
--- /dev/null
+++ b/flask_inputfilter/Validator/NotInArrayValidator.py
@@ -0,0 +1,33 @@
+from typing import Any, List, Optional
+
+from ..Exception import ValidationError
+from .BaseValidator import BaseValidator
+
+
+class NotInArrayValidator(BaseValidator):
+    """
+    Validator that checks if a value is in a given list of disallowed values.
+    """
+
+    def __init__(
+        self,
+        haystack: List[Any],
+        strict: bool = False,
+        error_message: Optional[str] = None,
+    ) -> None:
+        self.haystack = haystack
+        self.strict = strict
+        self.error_message = error_message
+
+    def validate(self, value: Any) -> None:
+        is_disallowed = value in self.haystack
+        is_type_mismatch = self.strict and not any(
+            isinstance(value, type(item)) for item in self.haystack
+        )
+
+        if is_disallowed or is_type_mismatch:
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is in the disallowed values "
+                f"'{self.haystack}'."
+            )
diff --git a/flask_inputfilter/Validator/NotValidator.py b/flask_inputfilter/Validator/NotValidator.py
new file mode 100644
index 0000000..d63f2fe
--- /dev/null
+++ b/flask_inputfilter/Validator/NotValidator.py
@@ -0,0 +1,31 @@
+from typing import Any, Optional
+
+from ..Exception import ValidationError
+from .BaseValidator import BaseValidator
+
+
+class NotValidator(BaseValidator):
+    """
+    Validator that inverts another validator.
+    """
+
+    def __init__(
+        self,
+        validator: BaseValidator,
+        error_message: Optional[str] = None,
+    ) -> None:
+        self.validator = validator
+        self.error_message = error_message
+
+    def validate(self, value: Any) -> None:
+        try:
+            self.validator.validate(value)
+        except ValidationError:
+            return
+
+        raise ValidationError(
+            self.error_message
+            or f"Validation of '{value}' in "
+            f"'{self.validator.__class__.__name__}' where "
+            f"successful but should have failed"
+        )
diff --git a/flask_inputfilter/Validator/README.md b/flask_inputfilter/Validator/README.md
index 54783df..74f5f48 100644
--- a/flask_inputfilter/Validator/README.md
+++ b/flask_inputfilter/Validator/README.md
@@ -8,25 +8,29 @@ The following validators are available in the `Validator` module:
 
 1. [`ArrayElementValidator`](ArrayElementValidator.py) - Validates each element of an array with its own defined InputFilter.
 2. [`ArrayLengthValidator`](ArrayLengthValidator.py) - Validates the length of an array.
-3. [`DateRangeValidator`](DateRangeValidator.py) - Validates that the date is within a specified range.
-4. [`FloatPrecisionValidator`](FloatPrecisionValidator.py) - Validates the precision of a float.
-5. [`InArrayValidator`](InArrayValidator.py) - Validates that the value is in the given array.
-6. [`InEnumValidator`](InEnumValidator.py) - Validates that the value is in the given enum.
-7. [`IsArrayValidator`](IsArrayValidator.py) - Validates that the value is an array.
-8. [`IsBase64ImageCorrectSizeValidator`](IsBase64ImageCorrectSizeValidator.py) - Validates that the value is a base64 encoded string.
-9. [`IsBase64ImageValidator`](IsBase64ImageValidator.py) - Validates that the value is a base64 encoded string.
-10. [`IsBooleanValidator`](IsBooleanValidator.py) - Validates that the value is a boolean.
-11. [`IsFloatValidator`](IsFloatValidator.py) - Validates that the value is a float.
-12. [`IsFutureDateValidator`](IsFutureDateValidator.py) - Validates that the value is a future date.
-13. [`IsHexadecimalValidator`](IsHexadecimalValidator.py) - Validates that the value is a hexadecimal string.
-14. [`IsInstanceValidator`](IsInstanceValidator.py) - Validates that the value is an instance of a class.
-15. [`IsIntegerValidator`](IsIntegerValidator.py) - Validates that the value is an integer.
-16. [`IsJsonValidator`](IsJsonValidator.py) - Validates that the value is a json string.
-17. [`IsPastDateValidator`](IsPastDateValidator.py) - Validates that the value is a past date.
-18. [`IsStringValidator`](IsStringValidator.py) - Validates that the value is a string.
-19. [`IsUUIDValidator`](IsUUIDValidator.py) - Validates that the value is a UUID.
-20. [`IsWeekdayValidator`](IsWeekdayValidator.py) - Validates that the value is a weekday.
-21. [`IsWeekendValidator`](IsWeekendValidator.py) - Validates that the value is a weekend.
-22. [`LengthValidator`](LengthValidator.py) - Validates the length of the value.
-23. [`RangeValidator`](RangeValidator.py) - Validates that the value is within a specified range.
-24. [`RegexValidator`](RegexValidator.py) - Validates that the value matches a regex pattern.
+3. [`DateAfterValidator`](DateAfterValidator.py) - Validates that the date is after a specified date.
+4. [`DateBeforeValidator`](DateBeforeValidator.py) - Validates that the date is before a specified date.
+5. [`DateRangeValidator`](DateRangeValidator.py) - Validates that the date is within a specified range.
+6. [`FloatPrecisionValidator`](FloatPrecisionValidator.py) - Validates the precision of a float.
+7. [`InArrayValidator`](InArrayValidator.py) - Validates that the value is in the given array.
+8. [`InEnumValidator`](InEnumValidator.py) - Validates that the value is in the given enum.
+9. [`IsArrayValidator`](IsArrayValidator.py) - Validates that the value is an array.
+10. [`IsBase64ImageCorrectSizeValidator`](IsBase64ImageCorrectSizeValidator.py) - Validates that the value is a base64 encoded string.
+11. [`IsBase64ImageValidator`](IsBase64ImageValidator.py) - Validates that the value is a base64 encoded string.
+12. [`IsBooleanValidator`](IsBooleanValidator.py) - Validates that the value is a boolean.
+13. [`IsFloatValidator`](IsFloatValidator.py) - Validates that the value is a float.
+14. [`IsFutureDateValidator`](IsFutureDateValidator.py) - Validates that the value is a future date.
+15. [`IsHexadecimalValidator`](IsHexadecimalValidator.py) - Validates that the value is a hexadecimal string.
+16. [`IsInstanceValidator`](IsInstanceValidator.py) - Validates that the value is an instance of a class.
+17. [`IsIntegerValidator`](IsIntegerValidator.py) - Validates that the value is an integer.
+18. [`IsJsonValidator`](IsJsonValidator.py) - Validates that the value is a json string.
+19. [`IsPastDateValidator`](IsPastDateValidator.py) - Validates that the value is a past date.
+20. [`IsStringValidator`](IsStringValidator.py) - Validates that the value is a string.
+21. [`IsUUIDValidator`](IsUUIDValidator.py) - Validates that the value is a UUID.
+22. [`IsWeekdayValidator`](IsWeekdayValidator.py) - Validates that the value is a weekday.
+23. [`IsWeekendValidator`](IsWeekendValidator.py) - Validates that the value is a weekend.
+24. [`LengthValidator`](LengthValidator.py) - Validates the length of the value.
+25. [`NotInArrayValidator`](NotInArrayValidator.py) - Validates that the value is not in the given array.
+26. [`NotValidator`](NotValidator.py) - Validates that inverts the result of another validator.
+26. [`RangeValidator`](RangeValidator.py) - Validates that the value is within a specified range.
+27. [`RegexValidator`](RegexValidator.py) - Validates that the value matches a regex pattern.
diff --git a/flask_inputfilter/Validator/RangeValidator.py b/flask_inputfilter/Validator/RangeValidator.py
index 87419c0..77d78cd 100644
--- a/flask_inputfilter/Validator/RangeValidator.py
+++ b/flask_inputfilter/Validator/RangeValidator.py
@@ -1,4 +1,4 @@
-from typing import Any
+from typing import Any, Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -11,9 +11,9 @@ class RangeValidator(BaseValidator):
 
     def __init__(
         self,
-        min_value: float = None,
-        max_value: float = None,
-        error_message: str = "Value '{}' is not within the range {} to {}.",
+        min_value: Optional[float] = None,
+        max_value: Optional[float] = None,
+        error_message: Optional[str] = None,
     ) -> None:
         self.min_value = min_value
         self.max_value = max_value
@@ -23,11 +23,8 @@ def validate(self, value: Any) -> None:
         if (self.min_value is not None and value < self.min_value) or (
             self.max_value is not None and value > self.max_value
         ):
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(
-                        value, self.min_value, self.max_value
-                    )
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' is not within the range of "
+                f"'{self.min_value}' to '{self.max_value}'."
+            )
diff --git a/flask_inputfilter/Validator/RegexValidator.py b/flask_inputfilter/Validator/RegexValidator.py
index 99c4bdd..fd9741d 100644
--- a/flask_inputfilter/Validator/RegexValidator.py
+++ b/flask_inputfilter/Validator/RegexValidator.py
@@ -1,4 +1,5 @@
 import re
+from typing import Optional
 
 from ..Exception import ValidationError
 from .BaseValidator import BaseValidator
@@ -13,17 +14,15 @@ class RegexValidator(BaseValidator):
     def __init__(
         self,
         pattern: str,
-        error_message: str = "Value '{}' does not match the "
-        "required pattern '{}'.",
+        error_message: Optional[str] = None,
     ) -> None:
         self.pattern = pattern
         self.error_message = error_message
 
     def validate(self, value: str) -> None:
         if not re.match(self.pattern, value):
-            if "{}" in self.error_message:
-                raise ValidationError(
-                    self.error_message.format(value, self.pattern)
-                )
-
-            raise ValidationError(self.error_message)
+            raise ValidationError(
+                self.error_message
+                or f"Value '{value}' does not match the required "
+                f"pattern '{self.pattern}'."
+            )
diff --git a/flask_inputfilter/Validator/__init__.py b/flask_inputfilter/Validator/__init__.py
index 62f12d6..436f222 100644
--- a/flask_inputfilter/Validator/__init__.py
+++ b/flask_inputfilter/Validator/__init__.py
@@ -25,5 +25,7 @@
 from .IsWeekdayValidator import IsWeekdayValidator
 from .IsWeekendValidator import IsWeekendValidator
 from .LengthValidator import LengthValidator
+from .NotInArrayValidator import NotInArrayValidator
+from .NotValidator import NotValidator
 from .RangeValidator import RangeValidator
 from .RegexValidator import RegexValidator
diff --git a/test/test_condition.py b/test/test_condition.py
index 6d7007b..16f80ce 100644
--- a/test/test_condition.py
+++ b/test/test_condition.py
@@ -358,16 +358,50 @@ def test_required_if_condition(self) -> None:
         self.inputFilter.add("field1")
         self.inputFilter.add("field2")
 
+        # Case 1: value is a single value
         self.inputFilter.addCondition(
             RequiredIfCondition("field1", "value", "field2")
         )
 
+        self.inputFilter.validateData({"field1": "not value"})
         self.inputFilter.validateData({"field2": "value"})
-        self.inputFilter.validateData({"field1": "value", "field2": "value"})
+        self.inputFilter.validateData(
+            {"field1": "value", "field2": "other value"}
+        )
 
         with self.assertRaises(ValidationError):
             self.inputFilter.validateData({"field1": "value"})
 
+        # Case 2: value is a list
+        self.inputFilter.add("field3")
+        self.inputFilter.add("field4")
+
+        self.inputFilter.addCondition(
+            RequiredIfCondition("field3", ["value1", "value2"], "field4")
+        )
+
+        self.inputFilter.validateData({"field4": "value2"})
+        self.inputFilter.validateData({"field3": "value1", "field4": "value"})
+        self.inputFilter.validateData({"field3": "value2", "field4": "value"})
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"field3": "value1"})
+
+        # Case 3: value is None
+        self.inputFilter.add("field5")
+        self.inputFilter.add("field6")
+        self.inputFilter.addCondition(
+            RequiredIfCondition("field5", None, "field6")
+        )
+
+        self.inputFilter.validateData({"field6": "value"})
+        self.inputFilter.validateData(
+            {"field5": "any_value", "field6": "value"}
+        )
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"field5": "any_value"})
+
     def test_string_longer_than_condition(self) -> None:
         """
         Test StringLongerThanCondition.
diff --git a/test/test_input_filter.py b/test/test_input_filter.py
index 3890466..c1a1660 100644
--- a/test/test_input_filter.py
+++ b/test/test_input_filter.py
@@ -1,10 +1,20 @@
 import unittest
 from unittest.mock import Mock, patch
 
+from flask import Flask, g, jsonify
+
 from flask_inputfilter import InputFilter
+from flask_inputfilter.Condition import BaseCondition
 from flask_inputfilter.Exception import ValidationError
+from flask_inputfilter.Filter import ToUpperFilter
 from flask_inputfilter.Model import ExternalApiConfig
-from flask_inputfilter.Validator import InArrayValidator
+from flask_inputfilter.Validator import (
+    InArrayValidator,
+    IsIntegerValidator,
+    IsStringValidator,
+    LengthValidator,
+    RegexValidator,
+)
 
 
 class TestInputFilter(unittest.TestCase):
@@ -15,6 +25,147 @@ def setUp(self) -> None:
 
         self.inputFilter = InputFilter()
 
+    @patch.object(InputFilter, "validateData")
+    def test_validate_decorator(self, mock_validateData) -> None:
+        mock_validateData.return_value = {"username": "test_user", "age": 25}
+
+        app = Flask(__name__)
+
+        class MyInputFilter(InputFilter):
+            def __init__(self):
+                super().__init__()
+                self.add(
+                    name="username",
+                    required=True,
+                    filters=[],
+                    validators=[],
+                )
+                self.add(
+                    name="age",
+                    required=False,
+                    default=18,
+                    filters=[],
+                    validators=[IsIntegerValidator()],
+                )
+
+        @app.route("/test", methods=["GET", "POST"])
+        @MyInputFilter.validate()
+        def test_route():
+            validated_data = g.validated_data
+            return jsonify(validated_data)
+
+        with app.test_client() as client:
+            response = client.get(
+                "/test", query_string={"username": "test_user"}
+            )
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(
+                response.json, {"username": "test_user", "age": 25}
+            )
+
+            response = client.post("/test", json={"username": "test_user"})
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(
+                response.json, {"username": "test_user", "age": 25}
+            )
+
+        app = Flask(__name__)
+
+        @app.route("/test-delete/<username>", methods=["DELETE"])
+        @MyInputFilter.validate()
+        def test_delete_route(username):
+            validated_data = g.validated_data
+            return jsonify(validated_data)
+
+        with app.test_client() as client:
+            response = client.delete("/test-delete/test_user")
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(
+                response.json, {"username": "test_user", "age": 25}
+            )
+
+        app = Flask(__name__)
+
+        @app.route("/test-unsupported", methods=["NOVALIDMETHOD"])
+        @MyInputFilter.validate()
+        def test_unsupported_route():
+            validated_data = g.validated_data
+            return jsonify(validated_data)
+
+        with app.test_client() as client:
+            response = client.get("/test-unsupported")
+            self.assertEqual(response.status_code, 405)
+
+    @patch.object(InputFilter, "validateData")
+    def test_validation_error_response(self, mock_validateData):
+        mock_validateData.side_effect = ValidationError("Invalid data")
+
+        class MyInputFilter(InputFilter):
+            def __init__(self):
+                super().__init__()
+                self.add(
+                    name="age",
+                    required=False,
+                    default=18,
+                    filters=[],
+                    validators=[IsIntegerValidator()],
+                )
+
+        app = Flask(__name__)
+
+        @app.route("/test", methods=["GET"])
+        @MyInputFilter.validate()
+        def test_route():
+            return "Success"
+
+        with app.test_client() as client:
+            response = client.get("/test", query_string={"age": "not_an_int"})
+
+        self.assertEqual(response.status_code, 400)
+        self.assertEqual(response.data.decode(), "Invalid data")
+
+    @patch.object(InputFilter, "validateData")
+    def test_custom_supported_methods(self, mock_validateData):
+        mock_validateData.return_value = {"username": "test_user", "age": 25}
+
+        class MyInputFilter(InputFilter):
+            def __init__(self):
+                super().__init__(methods=["GET"])
+
+                self.add(
+                    name="username",
+                    required=True,
+                    filters=[],
+                    validators=[],
+                )
+                self.add(
+                    name="age",
+                    required=False,
+                    default=18,
+                    filters=[],
+                    validators=[IsIntegerValidator()],
+                )
+
+        app = Flask(__name__)
+
+        @app.route("/test", methods=["GET", "POST"])
+        @MyInputFilter.validate()
+        def test_route():
+            validated_data = g.validated_data
+            return jsonify(validated_data)
+
+        with app.test_client() as client:
+            response = client.get(
+                "/test", query_string={"username": "test_user"}
+            )
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(
+                response.json, {"username": "test_user", "age": 25}
+            )
+
+            response = client.post("/test", json={"username": "test_user"})
+            self.assertEqual(response.status_code, 405)
+
     def test_optional(self) -> None:
         """
         Test that optional field validation works.
@@ -32,7 +183,7 @@ def test_default(self) -> None:
         Test that default field works.
         """
 
-        self.inputFilter.add("available", required=False, default=True)
+        self.inputFilter.add("available", default=True)
 
         # Default case triggert
         validated_data = self.inputFilter.validateData({})
@@ -52,18 +203,16 @@ def test_fallback(self) -> None:
         self.inputFilter.add("available", required=True, fallback=True)
         self.inputFilter.add(
             "color",
-            required=False,
+            required=True,
             fallback="red",
             validators=[InArrayValidator(["red", "green", "blue"])],
         )
 
-        # Fallback case triggert
         validated_data = self.inputFilter.validateData({"color": "yellow"})
 
         self.assertEqual(validated_data["available"], True)
         self.assertEqual(validated_data["color"], "red")
 
-        # Override fallback case
         validated_data = self.inputFilter.validateData(
             {"available": False, "color": "green"}
         )
@@ -71,6 +220,30 @@ def test_fallback(self) -> None:
         self.assertEqual(validated_data["available"], False)
         self.assertEqual(validated_data["color"], "green")
 
+    def test_fallback_with_default(self) -> None:
+        """
+        Test that fallback field works.
+        """
+
+        self.inputFilter.add(
+            "available", required=True, default=True, fallback=False
+        )
+        self.inputFilter.add(
+            "color",
+            default="red",
+            fallback="blue",
+            validators=[InArrayValidator(["red", "green", "blue"])],
+        )
+
+        validated_data = self.inputFilter.validateData({})
+
+        self.assertEqual(validated_data["available"], True)
+        self.assertEqual(validated_data["color"], "red")
+
+        validated_data = self.inputFilter.validateData({"available": False})
+
+        self.assertEqual(validated_data["available"], False)
+
     @patch("requests.request")
     def test_external_api(self, mock_request: Mock) -> None:
         """
@@ -83,7 +256,7 @@ def test_external_api(self, mock_request: Mock) -> None:
         mock_request.return_value = mock_response
 
         # Add a field where the external API receives its value
-        self.inputFilter.add("name", required=False, default="test_user")
+        self.inputFilter.add("name", default="test_user")
 
         # Add a field with external API configuration
         self.inputFilter.add(
@@ -120,26 +293,23 @@ def test_external_api_params(self, mock_request: Mock) -> None:
         mock_response.json.return_value = {"is_valid": True}
         mock_request.return_value = mock_response
 
-        # Add fields where the external API receives its values
-        self.inputFilter.add("name", required=False)
+        self.inputFilter.add("name")
 
-        self.inputFilter.add("hash", required=False)
+        self.inputFilter.add("hash")
 
-        # Add a field with external API configuration
         self.inputFilter.add(
             "is_valid",
             required=True,
             external_api=ExternalApiConfig(
                 url="https://api.example.com/validate_user/{{name}}",
                 method="GET",
-                params={"hash": "{{hash}}"},
+                params={"hash": "{{hash}}", "id": 123},
                 data_key="is_valid",
                 headers={"custom_header": "value"},
                 api_key="1234",
             ),
         )
 
-        # API returns valid result
         validated_data = self.inputFilter.validateData(
             {"name": "test_user", "hash": "1234"}
         )
@@ -150,10 +320,9 @@ def test_external_api_params(self, mock_request: Mock) -> None:
             headers={"Authorization": "Bearer 1234", "custom_header": "value"},
             method="GET",
             url=expected_url,
-            params={"hash": "1234"},
+            params={"hash": "1234", "id": 123},
         )
 
-        # API returns invalid status code
         mock_response.status_code = 500
         mock_response.json.return_value = {"is_valid": False}
         with self.assertRaises(ValidationError):
@@ -161,7 +330,6 @@ def test_external_api_params(self, mock_request: Mock) -> None:
                 {"name": "invalid_user", "hash": "1234"}
             )
 
-        # API returns invalid result
         mock_response.json.return_value = {}
         with self.assertRaises(ValidationError):
             self.inputFilter.validateData(
@@ -175,10 +343,62 @@ def test_external_api_fallback(self, mock_request: Mock) -> None:
         mock_response.json.return_value = {"name": True}
         mock_request.return_value = mock_response
 
+        self.inputFilter.add(
+            "username_with_fallback",
+            required=True,
+            fallback="fallback_user",
+            external_api=ExternalApiConfig(
+                url="https://api.example.com/validate_user",
+                method="GET",
+                params={"user": "{{value}}"},
+                data_key="name",
+            ),
+        )
+
+        validated_data = self.inputFilter.validateData(
+            {"username_with_fallback": None}
+        )
+        self.assertEqual(
+            validated_data["username_with_fallback"], "fallback_user"
+        )
+
+    @patch("requests.request")
+    def test_external_api_default(self, mock_request: Mock) -> None:
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.return_value = {}
+        mock_request.return_value = mock_response
+
         # API call with fallback
+        self.inputFilter.add(
+            "username_with_default",
+            default="default_user",
+            external_api=ExternalApiConfig(
+                url="https://api.example.com/validate_user",
+                method="GET",
+                params={"user": "{{value}}"},
+                data_key="name",
+            ),
+        )
+
+        validated_data = self.inputFilter.validateData({})
+        self.assertEqual(
+            validated_data["username_with_default"], "default_user"
+        )
+
+    @patch("requests.request")
+    def test_external_api_fallback_with_default(
+        self, mock_request: Mock
+    ) -> None:
+        mock_response = Mock()
+        mock_response.status_code = 400
+        mock_response.json.return_value = {"name": True}
+        mock_request.return_value = mock_response
+
         self.inputFilter.add(
             "username_with_fallback",
             required=True,
+            default="default_user",
             fallback="fallback_user",
             external_api=ExternalApiConfig(
                 url="https://api.example.com/validate_user",
@@ -195,6 +415,129 @@ def test_external_api_fallback(self, mock_request: Mock) -> None:
             validated_data["username_with_fallback"], "fallback_user"
         )
 
+    @patch("requests.request")
+    def test_external_invalid_api_response(self, mock_request: Mock) -> None:
+        """
+        Test that a non-JSON API response raises a ValidationError.
+        """
+        mock_response = Mock()
+        mock_response.status_code = 200
+        mock_response.json.side_effect = ValueError("Invalid JSON")
+        mock_request.return_value = mock_response
+
+        self.inputFilter.add(
+            "is_valid",
+            external_api=ExternalApiConfig(
+                url="https://api.example.com/validate",
+                method="GET",
+            ),
+        )
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({})
+
+    @patch("requests.request")
+    def test_external_api_response_with_no_data_key(
+        self, mock_request: Mock
+    ) -> None:
+        """
+        Test that an API response with no data key raises a ValidationError.
+        """
+        mock_response = Mock()
+        mock_response.status_code = 400
+        mock_response.json.return_value = {}
+        mock_request.return_value = mock_response
+
+        self.inputFilter.add(
+            "is_valid",
+            external_api=ExternalApiConfig(
+                url="https://api.example.com/validate",
+                method="GET",
+            ),
+        )
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({})
+
+    def test_multiple_validators(self) -> None:
+        """
+        Test that multiple validators are applied correctly.
+        """
+        self.inputFilter.add(
+            "username",
+            required=True,
+            validators=[
+                RegexValidator(r"^[a-zA-Z0-9_]+$"),
+                LengthValidator(min_length=3, max_length=15),
+            ],
+        )
+
+        validated_data = self.inputFilter.validateData(
+            {"username": "valid_user"}
+        )
+        self.assertEqual(validated_data["username"], "valid_user")
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"username": "no"})
+
+    def test_conditions(self) -> None:
+        """
+        Test that conditions are checked correctly.
+        """
+
+        class MockCondition(BaseCondition):
+            def check(self, data: dict) -> bool:
+                return data.get("age") > 18
+
+        self.inputFilter.add("age", required=True)
+        self.inputFilter.addCondition(MockCondition())
+
+        validated_data = self.inputFilter.validateData({"age": 20})
+        self.assertEqual(validated_data["age"], 20)
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"age": 17})
+
+    def test_global_filter_applied_to_all_fields(self) -> None:
+        self.inputFilter.add("field1")
+        self.inputFilter.add("field2")
+
+        self.inputFilter.addGlobalFilter(ToUpperFilter())
+
+        validated_data = self.inputFilter.validateData(
+            {"field1": "test", "field2": "example"}
+        )
+
+        self.assertEqual(validated_data["field1"], "TEST")
+        self.assertEqual(validated_data["field2"], "EXAMPLE")
+
+    def test_global_filter_with_no_fields(self) -> None:
+        self.inputFilter.addGlobalFilter(ToUpperFilter())
+
+        validated_data = self.inputFilter.validateData({})
+        self.assertEqual(validated_data, {})
+
+    def test_global_validator_applied_to_all_fields(self) -> None:
+        self.inputFilter.add("field1")
+        self.inputFilter.add("field2")
+        self.inputFilter.addGlobalValidator(IsStringValidator())
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"field1": 345, "field2": "example"})
+
+        validated_data = self.inputFilter.validateData(
+            {"field1": "test", "field2": "example"}
+        )
+
+        self.assertEqual(validated_data["field1"], "test")
+        self.assertEqual(validated_data["field2"], "example")
+
+    def test_global_validator_with_no_fields(self) -> None:
+        self.inputFilter.addGlobalValidator(IsIntegerValidator())
+
+        validated_data = self.inputFilter.validateData({})
+        self.assertEqual(validated_data, {})
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/test/test_validator.py b/test/test_validator.py
index dc06575..78acbdc 100644
--- a/test/test_validator.py
+++ b/test/test_validator.py
@@ -31,6 +31,8 @@
     IsWeekdayValidator,
     IsWeekendValidator,
     LengthValidator,
+    NotInArrayValidator,
+    NotValidator,
     RangeValidator,
     RegexValidator,
 )
@@ -877,6 +879,75 @@ def test_length_validator(self) -> None:
         with self.assertRaises(ValidationError):
             self.inputFilter.validateData({"name": "a"})
 
+    def test_not_in_array_validator(self) -> None:
+        """
+        Test NotInArrayValidator.
+        """
+
+        self.inputFilter.add(
+            "color",
+            validators=[NotInArrayValidator(["red", "green", "blue"])],
+        )
+
+        self.inputFilter.validateData({"color": "yellow"})
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"color": "red"})
+
+        self.inputFilter.add(
+            "color_strict",
+            validators=[NotInArrayValidator(["red", "green", "blue"], True)],
+        )
+
+        self.inputFilter.validateData({"color_strict": "yellow"})
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"color_strict": "red"})
+
+        self.inputFilter.add(
+            "custom_error",
+            validators=[
+                NotInArrayValidator(
+                    ["red", "green", "blue"],
+                    error_message="Custom error message",
+                )
+            ],
+        )
+
+        self.inputFilter.validateData({"custom_error": "yellow"})
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"custom_error": "red"})
+
+    def test_not_validator(self) -> None:
+        """
+        Test NotValidator that inverts another validator.
+        """
+
+        self.inputFilter.add(
+            "age",
+            validators=[NotValidator(IsIntegerValidator())],
+        )
+
+        self.inputFilter.validateData({"age": "not an integer"})
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"age": 25})
+
+        self.inputFilter.add(
+            "age",
+            validators=[
+                NotValidator(
+                    IsIntegerValidator(), error_message="Custom error message"
+                )
+            ],
+        )
+
+        self.inputFilter.validateData({"age": "not an integer"})
+
+        with self.assertRaises(ValidationError):
+            self.inputFilter.validateData({"age": 25})
+
     def test_range_validator(self) -> None:
         """
         Test that RangeValidator validates numeric values