# Certum
A dictionary validation library based on partial, composable and expressive rules.
## Why use it
In case you need to assert some propeties from a particular dictionary in a DSL manner without comparing the entire structure or asserting fields.
Certum comes with the following features:
- Easy to use
- English friendly declaration
- Error accumulation
- Customizable
- Anti KeyError
## Using Certum
You can't use certum package for the moment, coming soon.
## How it works
### Basic usage
Imagine you have a very long json and you want to verify that it contains the following informations:
- He should contains a key named 'name' containing a string.
- He should contains a key named 'entities' being a list containing unique elements.
- He should contains a key named 'nested' containing a key 'value' equals to 4.
```python
from certum import ensure, that
my_obj = {
"name": "hello",
"entities": [1, 3, 5],
"nested": {
"value": 4
}
}
validator = ensure(my_obj).respects(
that("name").is_instance_of(str),
that("entities").has_unique_elements(),
that("nested", "value").equals(4)
)
validator.check()
```
### Error handling
If there is errors, certum will accumulate and return errors elegantly:
```python
from certum import ensure, that
my_obj = {
"name": 2,
"entities": [1, 3, 3],
"nested": {
"value": 2
}
}
validator = (
ensure(my_obj)
.respects(
that("name").is_instance_of(str),
that("name").equals("Hello"),
that("entities").foreach(this.equals(1)),
that("nested", "value").equals(4),
)
)
validator.check()
# certum.exception.CertumException:
# [name] => The value is instance of int, expected str.
# [name] => The value is 2, expected Hello.
# [entities -> 2] => The value is 3, expected 1.
# [entities -> 1] => The value is 3, expected 1.
# [nested -> value] => The value is 2, expected 4.
```
### Strategies
Erros can be sorted, filtered and printed using different strategies.
As an example, you may want to try the GroupedPrinting strategy with the AlphabeticalSorting strategy, this will give you a list of errors like this:
```python
from certum import ensure, that, this
from certum.strategy.printing.grouped import GroupedPrinting
from certum.strategy.sorting.alphabetical import AlphabeticalSorting
my_obj = {
"name": 2,
"entities": [1, 3, 3],
"nested": {
"value": 2
}
}
validator = (
ensure(my_obj)
.respects(
that("name").is_instance_of(str),
that("name").equals("Hello"),
that("entities").foreach(this.equals(1)),
that("nested", "value").equals(4),
)
.using(GroupedPrinting(), AlphabeticalSorting())
)
validator.check()
# certum.exception.CertumException:
# entities -> 1 => The value is 3, expected 1.
# entities -> 2 => The value is 3, expected 1.
# name => The value is 2, expected Hello.
# The value is instance of int, expected str.
# nested -> value => The value is 2, expected 4.
```
