In this post to his site Amine Matmati shows you how to use Behat (with a bit of additional PHP) to test the contents of a rendered PDF file.

If you have a PDF generation functionality in your app, and since most of the libraries out there build the PDF content in an internal structure before outputting it to the file system (FPDF, TCPDF). A good way to write a test for it is to test the output just before the rendering process.

Recently however, and due to this process being a total pain in the ass, people switched to using tools like wkhtmltopdf or some of its PHP wrappers (phpwkhtmltopdf, snappy) that let you build your pages in html/css and use a browser engine to render the PDF for you, and while this technique is a lot more developer friendly, you loose control over the building process.

He shows how to get all of the required software installed including the smalot/pdfparser library used to read in the contents of the PDF file. He initializes a Behat test directory and writes a simple test, checking for a string of some "Lorem ipsum" text in the document's title and that it contains only one page. Some additional methods have to be created to integrate the PDF parsing and string location/page counting and code is included for each. When all the pieces are put in place, executing the test passes for both checks. You can find the code for the tutorial in this repository that also includes two sample PDFs to work with.