Setting up a test suite for the graph implementation

Before we conclude our tour of the in-memory graph implementation, we need to spend some time authoring a test suite that will execute the shared verification suite against the store implementation we just created. This can be achieved with only a handful of lines, as follows:

Since we are working with a pure, in-memory implementation, we can cheat and recreate the graph before running each test by providing a SetUpTest method that the gocheck framework will automatically invoke for us when running the test suite.