Mystery test coverage changes for two files

[GCHQDeveloper314]

Describe the bug
The following files appear to have variable levels of test coverage between runs:

• core/common-util/src/main/java/uk/gov/gchq/gaffer/commonutil/OneOrMore.java
• core/common-util/src/main/java/uk/gov/gchq/gaffer/commonutil/iterable/LimitedInMemorySortedIterable.java

This could be caused by problems with inconsistent tests for these files.

Expected behaviour
Code coverage should be consistent regardless of how many times the test is run.

Additional context
Codecov report showing these 'indirect changes' for a recent commit to develop.