In the case of retrofitting tests to code, one might divine the specification from the implementation. I will be doing this for PDF::Template over the next few weeks. However, the tests should still be testing the interface, not the code. I fully expect to find and fix several bugs over the next few weeks by thinking of things this way.

In the case of private methods ... that's an interesting point. Now, you have a private interface that you're testing against. You write tests against the private interface, then tests against the public interface. Just because you didn't publish the private interface doesn't mean it's not a black-box test. The tests for the private method are against the privately-published interface of the private method.

TDD tests shouldn't be driven by the implementation. Look at Pugs as a perfect example of this. Half the test-writers can't read Haskell to save their life, but it's still TDD.

---

---

• Are you posting in the right place? Check out Where do I post X? to know for sure.
• Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:

  <code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>

• Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
• Want more info? How to link or How to display code and escape characters are good places to start.