Fluent Assert

This library is built upon webmozart/assert and provides a fluent interface for assertions, which allows for a more compact set of assertions on the same value.

It is a useful tool for those who want to use webmozart/assert but prefer a more fluent interface.

Built with love ❤️

Installation

Use Composer to install the library.

composer require exeque/fluent-assert

Differences

There are a few differences between this library and webmozart/assert:

• The all* methods don't use the source methods in webmozart/assert.
  • They work as you would expect, but they use each() internally to apply the assertions to each value. See Iterative Assertions.
• The exception throw on failures are different.
  • \ExeQue\FluentAssert\Exceptions\InvalidArgumentException is thrown on failures.
    • It extends \Webmozart\Assert\InvalidArgumentException.
  • \ExeQue\FluentAssert\Exceptions\BulkInvalidArgumentException is thrown on grouped assertions
    • It extends \ExeQue\FluentAssert\Exceptions\InvalidArgumentException.
    • It provides multiple exceptions in the getExceptions() method.
    • See Grouped Assertions.
  • \ExeQue\FluentAssert\Exceptions\IndexedInvalidArgumentException is thrown on positional or iterative assertions
    • It extends \ExeQue\FluentAssert\Exceptions\InvalidArgumentException.
    • It provides the index of the failing assertion in the getIndex() method.
    • It provides the original message in the getOriginalMessage() method.
    • See Positional Assertions or Iterative Assertions.

Example

use ExeQue\FluentAssert\Assert;

$assert = Assert::for('foo bar');

// All methods from webmozart/assert are available
// The arguments are the same except for the first one (the value to assert).
$assert
    ->string()          // Webmozart/Assert::string(..., $message = '')
    ->startsWith('foo') // Webmozart/Assert::startsWith(..., $prefix, $message = '')
    ->endsWith('bar');  // Webmozart/Assert::endsWith(..., $suffix, $message = '')

// You can retrieve via the `value()` method.
$value = $assert->value(); // 'foo bar'

The example from webmozart/assert can be rewritten as:

use ExeQue\FluentAssert\Assert;

class Employee
{
    public function __construct($id)
    {
        Assert::for($id)
            ->integer('The employee ID must be an integer. Got: %s')
            ->greaterThan(0, 'The employee ID must be a positive integer. Got: %s');
    }
}

new Employee('foo bar');
// -> ExeQue\FluentAssert\Exceptions\InvalidArgumentException:
//    The employee ID must be an integer. Got: string

new Employee(-10);
// -> ExeQue\FluentAssert\Exceptions\InvalidArgumentException:
//    The employee ID must be a positive integer. Got: -10

Grouped Assertions

The fluent interface provides a and() and or() method to group assertions.

This is useful when you want to make multiple assertions at once and a singular combined error.

use ExeQue\FluentAssert\Assert;

$assert = Assert::for('fizz buzz');

// Using `and()` will throw an exception if any of the assertions fail.
// The errors will be combined into a single exception.
$assert->and(
    fn (Assert $assert) => $assert->startsWith('foo'),
    fn (Assert $assert) => $assert->endsWith('bar'),
);
// -> ExeQue\FluentAssert\Exceptions\BulkInvalidArgumentException:
//    Expected a value to start with "foo" (Got: "fizz buzz"), or expected a value to end with "bar" (Got: "fizz buzz").

// Using `or()` will only throw an exception if all the assertions fail.
// The errors will be combined into a single exception.
$assert->or(
    fn (Assert $assert) => $assert->startsWith('foo'),
    fn (Assert $assert) => $assert->startsWith('fizz'),
):
// -> Does not fail

$assert->or(
    fn (Assert $assert) => $assert->startsWith('foo'),
    fn (Assert $assert) => $assert->startsWith('bar'),
):
// -> ExeQue\FluentAssert\Exceptions\BulkInvalidArgumentException:
//    Expected a value to start with "foo" (Got: "fizz buzz"), or expected a value to start with "bar" (Got: "fizz buzz").

Iterative Assertions

The each() method allows you to iterate over an array or an ArrayAccess object and apply assertions to each value.

The errors thrown will have a prefix of failing index applied.

use ExeQue\FluentAssert\Assert;

$assert = Assert::for(['foo', 'bar', 'baz']);

$assert->each(
    fn (Assert $assert) => $assert->string()->length(3)
);

$assert->each(
    fn (Assert $assert) => $assert->inArray(['foo', 'bar'])
);
// -> ExeQue\FluentAssert\Exceptions\IndexedInvalidArgumentException:
//    [2]: Expected one of: "foo", "bar". Got: "baz"

The IndexedInvalidArgumentException can provide the index that failed use getIndex() and the original message using getOriginalMessage().

An alternative version eachKey is available to apply assertions to the keys of an iterable.

### Positional Assertions

The `at()` method allows you to assert a value at a specific index in an array or an `ArrayAccess` object.

It automatically calls `keyExists()` on the index before applying the assertion.

The errors thrown will have a prefix of failing index applied.

```php
use ExeQue\FluentAssert\Assert;

// Works with integer indices
$assert = Assert::for(['foo', 'bar', 'baz']);
$assert->at(0, fn (Assert $assert) => $assert->eq('foo'));

// Works with string indices
$assert = Assert::for(['foo' => 'bar', 'baz' => 'qux']);
$assert->at('baz', fn (Assert $assert) => $assert->eq('qux'));

$assert = Assert::for(['foo' => 'bar']);
$assert->at('foo', fn (Assert $assert) => $assert->eq('fizz'));
// -> ExeQue\FluentAssert\Exceptions\IndexedInvalidArgumentException:
//    [foo]: Expected a value equal to "fizz". Got: "bar"

Conditional Assertions

Sometimes you only want to apply certain assertions if a condition is met or not. The when() method allows you to do this.

use ExeQue\FluentAssert\Assert;
use ExeQue\FluentAssert\ConditionAssert;

$assert = Assert::for(['foo', 'bar', 'baz']);

// The `when()` method takes a callable that may return a boolean value
// or a `ConditionAssert` object.
$assert->when(
    // Any truthy value will be considered true
    condition: fn (Assert $assert) => true,
    // [Required] Assertions to apply if the condition is true 
    then: fn (Assert $assert) => null,
    // [Optional] Assertions to apply if the condition is false
    otherwise: fn (Assert $assert) => null,
);

// If the condition uses the `Assert` provided as an argument and
// returns null (or nothing) and the inner assertion did not fail,
// then that is considered true.

$assert = Assert::for('foo bar');

$assert->when(
    function (Assert $assert) {
        $assert->string(); // Returns nothing
    },
    fn(Assert $assert) => null, // Is called
);

$assert->when(
    function (Assert $assert) {
        $assert->string();
        
        return null;
    },
    fn(Assert $assert) => null, // Is called
);

$assert->when(
    function (Assert $assert) {
        $assert->isArray();
    },
    fn(Assert $assert) => null, // Is not called
    fn(Assert $assert) => null, // Is called
);

Inverted Assertions

The not() method allows you to invert the assertion. This is useful when the assertions MUST fail.

use ExeQue\FluentAssert\Assert;

$assert = Assert::for([1, 2, 3, 4]);

$assert->not(
    fn (Assert $assert) => $assert->arrayContains(3),
    'Input cannot contain the number 3'
);

Assertions

All assertions from webmozart/assert are available. See here

An extended implementation of webmozart/assert is available in the ExeQue\FluentAssert\Base class.

The following additional assertions are available:

Method	Description
hasIndices($value, string $message = '')	Check that a value has indices (array or ArrayAccess)
arrayContains($array, mixed $value, string $message = '')	Check that a value contains another value
type($value, string $type, string $message = '')	Check that a value is of a certain type (using get_debug_type())
publicPropertyExists($value, string $name, string $message = '')	Check that a value has a public property
protectedPropertyExists($value, string $name, string $message = '')	Check that a value has a protected property
privatePropertyExists($value, string $name, string $message = '')	Check that a value has a private property
staticPropertyExists($value, string $name, string $message = '')	Check that a value has a static property
instancedPropertyExists($value, string $name, string $message = '')	Check that a value has an instanced property
enumCaseExists($value, string $enumClass, string $message = '')	Check that a value is a case in an enum
enumValueExists($value, string $enumClass, string $message = '')	Check that a value is a value in an enum
nullOr($value, callable $callback)	Execute the callback if the value is not null

Development

The library uses code generation to create definitions for all methods present in webmozart/assert.

To trigger the generation run:

composer build

Testing

You can run the tests using the following command:

composer test

License

This library is open-sourced software licensed under the MIT license.

Appreciation

Big thanks to Bernard Schussek (and community) for the webmozart/assert.

It is one of the first dependencies I include in any project and I use it extensively.