As a software engineer
I want to have good code coverage of PointerService
So that I can have confidence that changes won't break existing functionality

Given mockall may not currently a dependency of anttp
When adding unit tests to PointerService
Then add mockall as test dependency in cargo.toml

Given mockall can be used to mock struct impl dependencies
When adding unit tests to PointerService
Then create mockall mocks to create mock instances of PointerCachingClient and ResolverService
And use these mocks to test PointerService methods
And use mock! to define test doubles whose actions can be mocked

Implementation Notes

- Place any unit tests at the bottom of the same file as the associated production code
- Increment patch version of anttp package in Cargo.toml
- Create a copy of this issue description and save to /spec using the name of this issue as the filename (with lower underscore case, starting with the 5 char padded issue number, e.g. 00001_issue_title.txt)
- Review https://docs.rs/mockall/latest/mockall/ for documentation and examples
- Fix failing unit tests in PointerService and improve coverage