Add test coverage

[diversemix]

Description

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• a summary of the changes
• links to any related issue/ticket
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• details of any dependency updates that are required for this change

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Type of change

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How Has This Been Tested?

Please describe the tests that you added to verify your changes.

Reviewer Checklist

• The PR represents a single feature (small drive-by fixes are also ok)
• The PR includes tests that are sufficient for the level of risk
• The code is sufficiently commented, particularly in hard-to-understand areas
• Any required documentation updates have been made
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• No FIXMEs remain

[katybaulch]

Nice one!

[katybaulch]

lgtm :)