Class 'Imagick' not found

I need Imagick for my phpunit tests but it doesn’t seem to be available. What do I need to do to install or enable it? I’ve tried apt-get install -y php5-imagick but tells me that extension is already installed.

Here is a snippet of my phpunit test output.

phpunit
PHPUnit 4.8.21 by Sebastian Bergmann and contributors.

...................................................PHP Fatal error:  Class 'Imagick' not found in /home/ubuntu/novus-api-laravel/app/Http/Controllers/v4/Images/ImagesController.php on line 56

I’ve configured the build for PHP 5.6.14.