phpunit mock with partially known array expected: what are the correct constraints?

Here's a quick-and-dirty custom constraint to check that the passed array contains at least the given entries (key/value pairs). Add it to your custom testing framework or PHPUnit fork. Note that it uses == equality so that a key/mapping of '5' will match 5.

class ArrayHasEntries extends PHPUnit_Framework_Constraint
{
    /**
     * @var array
     */
    protected $array;

    /**
     * @param array $array
     */
    public function __construct(array $array)
    {
        $this->array = $array;
    }

    /**
     * Evaluates the constraint for parameter $other. Returns TRUE if the
     * constraint is met, FALSE otherwise.
     *
     * @param mixed $other Value or object to evaluate.
     * @return bool
     */
    protected function matches($other)
    {
        foreach ($this->array as $key => $value) {
            if (!array_key_exists($key, $other) || $other[$key] != $value) {
                return false;
            }
        }
        return true;
    }

    /**
     * Returns a string representation of the constraint.
     *
     * @return string
     */
    public function toString()
    {
        return 'has the entries ' . PHPUnit_Util_Type::export($this->array);
    }

    /**
     * Returns the description of the failure
     *
     * The beginning of failure messages is "Failed asserting that" in most
     * cases. This method should return the second part of that sentence.
     *
     * @param  mixed $other Evaluated value or object.
     * @return string
     */
    protected function failureDescription($other)
    {
        return 'an array ' . $this->toString();
    }
}