Add testing-only operations that validate certain properties of the workflow

[mxgrey]

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Description

The extreme extensibility of how operations are designed means that we could provide some operations in the testing module that are purely for testing purposes, to validate that other operations are working as intended. This will be a running list of possible testing operations:

• Verify that an operation was cleaned as intended (useful for testing trim operations)
• Count how many times an operation was reached per session