2fa9a8ec86
Makes it possible to compactly provide a delibrately invalid signature for use with CHECK(MULTI)SIG. For instance with BIP19 if m != n invalid signatures need to be provided in the scriptSig; prior to this change those invalid signatures would need to be large DER-encoded signatures. Note that we may want to further expand on this change in the future by saying that only OP_0 is a "valid" invalid signature; BIP19 even with this change is inherently malleable as the invalid signatures can be any validly encoded DER signature.
Notes
The sources in this directory are unit test cases. Boost includes a unit testing framework, and since bitcoin already uses boost, it makes sense to simply use this framework rather than require developers to configure some other framework (we want as few impediments to creating unit tests as possible).
The build system is setup to compile an executable called "test_bitcoin" that runs all of the unit tests. The main source file is called test_bitcoin.cpp, which simply includes other files that contain the actual unit tests (outside of a couple required preprocessor directives). The pattern is to create one test file for each class or source file for which you want to create unit tests. The file naming convention is "<source_filename>_tests.cpp" and such files should wrap their tests in a test suite called "<source_filename>_tests". For an examples of this pattern, examine uint160_tests.cpp and uint256_tests.cpp.
For further reading, I found the following website to be helpful in explaining how the boost unit test framework works: http://www.alittlemadness.com/2009/03/31/c-unit-testing-with-boosttest/.