Allow partial comparison of slices in asserts

[alembiewski]

Edit 2025-02-03:

Note the recently added CEL support which should help with this issue

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What would you like to be added:

It would be great to check only the subset of a slice in a test step assertion. Currently, it is required to specify all the array elements, otherwise, a test fails with slice length mismatch error.

Why is this needed:

Here are some real-life pain points:

• if istio injection is enabled, a sidecar is running alongside with the main container in a pod, and it needs to be reflected in test assertions;
• testing mutating webhook, which updates environment variables or volume/volume mounts for some container in a pod, and a test case checks the applied patch;
• pod's status conditions (say, the goal of a test step is to check the only one, final condition);
• and so on

[kensipe]

@alembiewski could you provide an example of what is required today and what you would like to see (yaml examples will help visualize). This seems valuable.

[kensipe]

we need enough info to create a kep

[alembiewski]

Here is the example: let's say we have a custom resource TrainingJob, which describes some machine-learning training job, and it has a status.conditions[] field (slice). The job goes through several conditions before it reaches the final state. In my test case, I want to check the job is succeeded. Currently, to work-around the slice length mismatch error, my assert file looks like this:

kind: TrainingJob
metadata:
  name: ml-job
status:
  conditions:
  - reason: JobCreated      # I have to provide all the intermediate conditions here
  - reason: JobRunning      # to make kuttl happy
  - reason: JobSucceeded   <-- this is what I actually want to test
    status: "True"
    type: Succeeded

This is how I would like my assert to be:

kind: TrainingJob
metadata:
  name: ml-job
status:
  conditions:
  - reason: JobSucceeded
    status: "True"
    type: Succeeded

So the problem is that I have to specify all the conditions (but this could be env variables, volumes - any property with array type).

[kensipe]

This is related to #75
Looking for better array support in asserts. Looking for:

1. Disregard order to array
2. Partial array support (only assert what is expressed)