Projects using Test::Nginx to drive their test suites usually have a common directory layout and common test file name patterns to organize their tests. This makes it easy for the user to reason about the location of the test suite in a project source tree and the usage of the tests. It is not really required, however, to use this common convention; it is just highly recommended.

By convention, such projects have a t/ directory at the root of their source tree where test files reside in. Each test file contains test cases that are closely related in some way and has the file extension .t to easily identify themselves as "test files". Below is the directory tree structure of a real-world test suite inside the headers-more-nginx-module project:

When you have many test files, you can also group them further with sub-directories under t/. For example, in the lua-nginx-module project, we have sub-directores like 023-rewrite/ and 024-access/ under its t/ directory.

In essence, each .t file is a Perl script file runnable by either perl or Perl’s universal test harness tool named prove. We usually use the prove command-line utility to run such .t files to obtain test results. Although .t files are Perl scripts per se, they usually do not have much Perl code at all. Instead, all of the test cases are declared as cleanly formatted "data" in these .t files.