Basic NGF Testing Framework

[mpstefan]

As a maintainer of NGF
I want basic utility functions to quickly setup an environment to test in
So that I can automate my functional and non-functional testing of NGF.

Background

Although much of our functional testing is covered by Gateway SIG's conformance tests, we have built a number of manual non-functional tests that need to be automated. As we continue to expand our feature set, we will also need additional functional testing on top of the conformance tests. To achieve continuous testing efficiently, we will first need a testing framework to automate the more tedious parts of the process that can be re-used when tests are automated.

Acceptance Criteria

• A set of utility functions are created that setup a complete testing environment for NGF so that no additional common actions need to be taken in the individual tests.

### Tasks
- [ ] #1218
- [ ] #985
- [ ] https://github.com/nginxinc/nginx-gateway-fabric/issues/1229
- [x] https://github.com/nginxinc/nginx-gateway-fabric/issues/1234

For Discussion

• Are there any additional common utilities we will need to avoid code duplication when automating our non-functional tests?