test: fix flakes in controller and registry tests

[LukeAVanDrie]

What type of PR is this?

/kind flake

What this PR does / why we need it:

Fixes two test flakes in the Flow Control layer (TestFlowController_EnqueueAndWait and TestFlowRegistry_GarbageCollection).

1. Controller Flake: Logic Race with RealClock

• OnReqCtxTimeoutAfterDistribution used a frozen FakeClock for the request timestamp but context.WithDeadline (which uses the system wall clock) for the deadline. CI/CD latency or slow startup (simulated locally with a 35ms sleep) caused the deadline to expire immediately relative to wall time, failing the test.
• This PR refactorsnewUnitHarness to accept options and injected clock.RealClock{} for this specific test case. This ensures the request timestamp and deadline check rely on the same time source.

2. Registry Flake: Background GC Race

• TestFlowRegistry_GarbageCollection/ShouldCollectIdleFlow failed intermittently because the background GC loop (enabled by default) raced with the test’s manual GC trigger. This sometimes caused the flow to be collected before the test asserted its state.
• This PR sets manualGC: true for this test case, preventing the background loop from interfering with deterministic test steps.

Reproduced flakes and verified fixes by injecting time.Sleep(35 * time.Millisecond) into newUnitHarness (for the controller test) and running:

go test -race -count=5000 -v -failfast -test.fullpath=true \
  -run ^TestFlowController_EnqueueAndWait$/^Lifecycle$/^OnReqCtxTimeoutAfterDistribution$ \
  sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/controller

go test -race -count=5000 -v -failfast -test.fullpath=true \
  -run ^TestFlowRegistry_GarbageCollection$/^ShouldCollectIdleFlow$ \
  sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/registry

Which issue(s) this PR fixes:

Fixes #2248
Fixes #2249

Does this PR introduce a user-facing change?:

NONE

[k8s-ci-robot]

@LukeAVanDrie: The label(s) kind/test cannot be applied, because the repository doesn't have them.

Details

In response to this:

What type of PR is this?

/kind test

What this PR does / why we need it:

Fixes two test flakes in the Flow Control layer (TestFlowController_EnqueueAndWait and TestFlowRegistry_GarbageCollection).

1. Controller Flake: Logic Race with RealClock

• OnReqCtxTimeoutAfterDistribution used a frozen FakeClock for the request timestamp but context.WithDeadline (which uses the system wall clock) for the deadline. CI/CD latency or slow startup (simulated locally with a 35ms sleep) caused the deadline to expire immediately relative to wall time, failing the test.
• This PR refactorsnewUnitHarness to accept options and injected clock.RealClock{} for this specific test case. This ensures the request timestamp and deadline check rely on the same time source.

2. Registry Flake: Background GC Race

• TestFlowRegistry_GarbageCollection/ShouldCollectIdleFlow failed intermittently because the background GC loop (enabled by default) raced with the test’s manual GC trigger. This sometimes caused the flow to be collected before the test asserted its state.
• This PR sets manualGC: true for this test case, preventing the background loop from interfering with deterministic test steps.

Reproduced flakes and verified fixes by injecting time.Sleep(35 * time.Millisecond) into newUnitHarness (for the controller test) and running:

go test -race -count=5000 -v -failfast -test.fullpath=true \
 -run ^TestFlowController_EnqueueAndWait$/^Lifecycle$/^OnReqCtxTimeoutAfterDistribution$ \
 sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/controller

go test -race -count=5000 -v -failfast -test.fullpath=true \
 -run ^TestFlowRegistry_GarbageCollection$/^ShouldCollectIdleFlow$ \
 sigs.k8s.io/gateway-api-inference-extension/pkg/epp/flowcontrol/registry

Which issue(s) this PR fixes:

Fixes #2248
Fixes #2249

Does this PR introduce a user-facing change?:

NONE

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes-sigs/prow repository.

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[ahg-g]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, LukeAVanDrie

The full list of commands accepted by this bot can be found here.

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• OWNERS [ahg-g]

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[ahg-g]

/retest