test: Add mocking

[andreaangiolillo]

Proposed changes

This PR adds mocking to the tools/cli

Checklist

• I have signed the MongoDB CLA
• I have added tests that prove my fix is effective or that my feature works

Further comments

[AgustinBettati]

[q] Not strictly related to this PR but was curious if there are alternatives to having a license header placed in all files, such as a LICENSE file at the root of the project.

[gssbzn]

for apache should be both

[gssbzn]