This is an example of a library. You may see a list of other libraries used on Rosetta Code at Category:Solutions by Library.
Wren-assert is a module which adds support for assertions to the Wren programming language.
It's use is subject to the MIT License.
The following examples assume that the source code is copied to a file called assert.wren which is then placed in the same directory as the importing script so the command line interpreter can find it.