Re: A simple unit test framework

Pete Becker <>
Fri, 04 May 2007 19:39:21 -0400
anon wrote:

Pete Becker wrote:

Ian Collins wrote:

Pete Becker wrote:

nw wrote:

I previously asked for suggestions on teaching testing in C++. Based
on some of the replies I received I decided that best way to proceed
would be to teach the students how they might write their own unit
test framework, and then in a lab session see if I can get them to
write their own. To give them an example I've created the following
UTF class (with a simple test program following). I would welcome and
suggestions on how anybody here feels this could be improved:

A fool with a tool is still a fool. The challenge in testing is not
management, but designing test cases to cover the possible failures in
the code under test. That's something that most developers don't do
well, because their focus is on getting the code to run.

Unless the test are written first!

You can't do coverage analysis or any other form of white-box testing
on code that hasn't been written. There is a big difference between a
tester's minset and a develper's mindset, and it's very hard for one
person to do both.

The latest trends are to write tests first which demonstrates the
requirements, then code (classes+methods). In this case you will not
have to do a coverage, but it is a plus.

That's not what coverage analysis refers to. Coverage analysis takes the
test cases that you've written and measures (speaking a bit informally)
how much of the code is actually tested by the test set. You can't make
that measurement until you've written the code.

This way, the code you write
will be minimal and easier to understand and maintain.
I agree this way looks harder (and I am not using it), but I am sure
once you get use to it - your programming skills will improve drastically

When you write tests before writing code you're only doing black box
testing. Black box testing has some strengths, and it has some
weaknesses. White box testing (which includes coverage analysis)
complements black box testing. Excluding it because of some dogma about
only writing tests before writing code limits the kinds of things you
can discover through testing.

The problem is that, in general, you cannot test every possible set of
input conditions to a function. So you have to select two sets of test
caes: those that check that mainline operations are correct, and those
that are most likely to find errors. That second set requires knowledge
of how the code was written, so that you can probe its likely weak spots.


    -- Pete
Roundhouse Consulting, Ltd. (
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." (

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