EvilUnit_design.txt

This library is intended to reduce the labour involved in writing test cases for C.

1/ The implementation is C89. It compiles cleanly under gcc and clang, will check MSVC at some point.

2/ Tests will self-install. There is no need to write a function prototype elsewhere, or to register the test in a suite somewhere. 

3/ Easy to use in existing projects. Specifically, no external dependencies and an easy compilation model.

The premise is to write a set of related test function using approximately familiar syntax, MODULE(foobar){...}. Each module is compiled to a single external function, called evilunit_node_something, which allows functions within the library to traverse the graph of test cases. Provided one file is marked "main", or "root", to provide a starting point, control can be applied to how the test modules are executed. At present, a depth first search from the root node creates a set of test modules which are executed leaf first, sequentially, avoiding running the same test twice.

There is a choice to be made between header-only and header + source.

Header + source:
Faster compilation
Wholly opaque datastructures
Header disappears entirely under the preprocessor

Header only:
Easier to integrate with build systems
Will emit a warning if #included, but the MODULE(){} construct is not used

As far as the implementation of this library is concerned, it is better to be header + source. As far as the clients are concerned, it is easier to have a single file on the include path. 

Previously, this was header + source. Recently this has changed to header-only. The EvilUnit.c file contains self-test code only.