Update `docs/testing` with updated step testing patterns

[ndowmon]

Awesome! Would you mind adding this to the development documentation please? I'd also love to see a task created to update the integration-template!

I'd like to make some minor updates to toMatchDirectRelationshipSchema, toMatchGraphObjectSchema, and add the toMatchStepMetadata matcher we discussed previously. Then go back and update docs/testing and integration-template

Originally posted by @ndowmon in https://github.com/JupiterOne/sdk/pull/611#discussion_r803792190

See #613 #614 #615