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T-Regex Development and Contributing rules

There are a few rules that we believe must be obeyed, while developing and maintaining T-Regx:

  • Lack of fake TDD
  • Lack of any inconsistencies
  • Simple and clean design
  • Lack of unnecessary performance overhead, if it can be easily avoided

Fake TDD

In presence of overwhelming fashion for scrum teams, agile approaches, tdd, oop and what not - one must understand what T-Regx understands as TDD, which is not always the same as what others might consider TDD.

  • It's not just about writing tests before implementation
  • It's not only about dependency injection and ensuring a testable class
  • It's not just about writing additional test cases while the implementation is being developed
  • It's not only about using mocks, separation of concerns, loose coupling between tests and logic, etc


  • It's also about being able to recognize that - if a certain testcase tests a feature of class A and logic of the feature is delegated to class B, then tests for class B should not test that feature - because it's already covered by class A tests.
  • It's also about developing a feature, while understanding:
    • what feature (or what element of the feature) does your test validate. It's crucial. A testcase should test only one such element. Ideally, that part should only be tested once.
    • why did you write another test:
      • isn't that part already covered?
      • does the situation you're testing against have any possibility of occurring?
      • does this testcase test the same feature as previous test, but with different parameters?
  • It's also about one's discipline to not only test the Happy Paths, but also exceptions, errors and unexpected input values.

Fake TDD can be easily spotted by slightly altering a single value in a codebase (changing true to false, commenting a line out, replacing if conditions with if(true)). If all the tests still pass after the change - the edited file wasn't written with TDD in mind.

Ideal TDD

T-Regx contributors must take for granted that:

  • Coverage is not a determinant of a well tested code. One can achieve 100% coverage with little effort and still encounter an enormous number of bugs.

    Coverage means:

    • Not covered parts are definitely not tested
    • Covered parts are not necessarily tested

    That's it. No more information can be obtained from coverage.

  • A class that has coverage hits is not necessarily tested. To verify that, one should get acquainted with:

    • Unit tests of the class
    • Unit tests of clients having this class as a dependency
    • Integration testcases that test behaviour of the class/feature implemented by the class (also in an indirect way)

    Only once done that, one is able to define which parts of the class are covered by tests and which are not.

  • There is no automatic tool that can tell you whether a file is tested. You need to read the tests, understand what parts are covered and what not.

  • There is no rule, so that each Foo class should have a corresponding FooTest class. You should choose your tests accordingly:

    • Integration - You'd like to test behaviour - then test only the part of your interface that's relevant to the feature domain, and not each element separately - write the smallest tests possible. Try to keep coupling of tests with logic as low as possible.


      • If possible, any dependencies should be real instances, instead of mocks. If instantiating becomes too complicated, occasional mocks are allowed, to make tests easier to read and edit.
    • Feature (a.k.a. "end to end") - This category has two goals:

      • Ensure that a certain functionality works "out of the box" (as if used by an end user).
      • Ensure that each dependency is integrated properly with other dependencies.


      • There should be as least tests in this category as possible (preferably 1 per functionality). More throughout testcases should be in Unit or Integration.
      • Each test-case must be created from pattern() function or one of Pattern factory methods.
    • Unit - There's a need to test a complicated feature of a class with a lot of corner-cases?

      Fine - you must couple a class to a test, and face the consequence that refactoring outside the class is not possible (cause you'd also have to adapt unit tests).


      • 100% of dependencies must be mocked. Only a change in the tested class can cause the test to fail.
    • Functional - The name may be a bit misleading, tests in Functional cover T-Regx's contract with PHP methods, errors, warnings, etc.


      • Tests for breaking changes between PHP versions should be in Functional
      • Tests for preg_ and preg:: should be in Functional


Avoid inconsistencies

We value consistency. Knowing a part of a library, should aid in learning the rest of it.

Keep in mind:

  • When editing a feature, see if there's also a similar feature. Consider, whether they both should be edited, or only the one?

Simple and clean design

We'd like you to try to avoid unnecessary setters and getters, just for the sake of them. All classes, whichever are fit for it, should be immutable. If there's a need for an object that has to persists state, it should be extracted to a dedicated class that's sole purpose is to maintain the state.


Recently, we started using Fully Qualified Names for global PHP functions, for the sake of performance. To keep it consistent, we also added a composer command which helps us find any unqualified functions. Use it like so

./composer.phar fqn


php composer.phar fqn
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