ReadFileTree reads a file tree rooted at the given relative path.

SortFileTree sorts a whole file subtree and returns it.

Cage wraps a test cage.Cage and replaces the command's path and args hijacked by Encage() with values appropriate for tests.

HTTPServerFactory represents a factory of HTTP servers for testing.

ProblemBundleFactory creates problem bundles for tests.

ProgramFactory creates program source codes for tests.