These instances of marks.Raw usage were semantically only testing the
properties of combining multiple marks. Testing this with an arbitrary
value for the mark is just as valid and clearer.
Some function errors include values derived from arguments. This commit
is the result of a manual audit of these errors, which resulted in:
- Adding a helper function to redact sensitive values;
- Applying that helper function where errors include values derived from
possibly-sensitive arguments;
- Cleaning up other errors which need not include those values, or were
otherwise incorrect.