Add envtest integration tests for kube controller

[AryanP123]

Fixes #2486

Summary by CodeRabbit

• Documentation
  • Added an integration testing README covering envtest setup, expected layout, and how to run integration tests.
• Tests
  • Added a Kubernetes controller integration test harness using envtest with shared lifecycle management.
  • Added new integration coverage for Site and Site with Listener, plus reusable controller test helpers.
• New Features
  • Introduced a test-integration Make target with configurable TESTFLAGS and ENVTEST_K8S_VERSION.
• Chores
  • Updated Go module dependencies to newer versions, including additional indirect tooling for envtest/controller-runtime.

[AryanP123]

@ajssmith @fgiorgetti @c-kruse Thoughts on this set up? For now just added integration tests for skupper/internal/kube/controller/controller.go. Didn't want to crowd the location of production files with more test files as unit tests typically already exist there.

[ajssmith]

Suggest a separate issue/pr for changes to NewClient as scope separate/independent from envtest integration

[AryanP123]

issue: #2506
pr: #2507

[c-kruse]

Suggestion for the setup-envtest tool and envtest system dependencies.

We should look at using a go tool to pin a setup-envtest version so that everyone doesn't immediately begin to drift and we don't need to make assumptions about the go binary path.

[coderabbitai]

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Reviewing files that changed from the base of the PR and between cfeb6ad and 5f9067a.

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• tests/integration/README.md

✅ Files skipped from review due to trivial changes (1)

• tests/integration/README.md

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📝 Walkthrough

Walkthrough

Adds envtest-based integration testing for the Skupper Kubernetes controller, including dependency updates, a shared test harness, controller integration tests, a Makefile target, and documentation.

Changes

Kube Controller Integration Tests

Layer / File(s)	Summary
Go module dependencies for controller-runtime and envtest go.mod	Updates github.com/spf13/pflag to v1.0.6, adds indirect dependencies github.com/blang/semver/v4, github.com/evanphx/json-patch/v5, github.com/spf13/afero, go.uber.org/multierr, go.uber.org/zap, and sigs.k8s.io/controller-runtime, and adds the setup-envtest tool directive.
envtest suite bootstrap and controller lifecycle tests/integration/kube/controller/suite_test.go	TestMain starts envtest with CRD base paths, starts a shared controller, and shuts both down after the test run. startSharedController configures the controller environment, creates the envtest-backed client, ensures the installation namespace exists, and runs the controller in a goroutine. stopSharedController closes the stop channel and waits for shutdown. testContext, setup(t), and createNamespace provide per-test access to the shared client and namespace creation.
Test helper utilities tests/integration/kube/controller/helpers_test.go	Adds waitFor for retry-based polling, retryOnNotFound for Kubernetes NotFound handling, listenerWithHostPort for Listener fixtures, routerSelector for router label selection, and verifyStatus for checking status type, message, and expected conditions.
Site and Listener integration tests tests/integration/kube/controller/site_test.go, tests/integration/kube/controller/listener_test.go	TestSimpleSite creates a Site, waits for the configured condition, and validates the resulting Site status and router Deployment labels/container count. TestSiteWithListener creates a Listener, waits for the listener and Service, then checks the Site status, router Deployment label, Service selector and port, listener label, and router ConfigMap transport configuration.
Makefile test-integration target and environment variables tests/Makefile	Adds SKUPPER_ROOT, TESTFLAGS, and ENVTEST_K8S_VERSION, and introduces the test-integration target that resolves envtest assets, exports KUBEBUILDER_ASSETS, and runs the integration controller test package with -tags=integration.
Integration test documentation tests/integration/README.md	Documents the envtest-based integration test purpose, repository layout, setup-envtest prerequisites and version pinning, run instructions from different working directories, USE_EXISTING_CLUSTER=true usage, and expected runtime and teardown notes.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely summarizes the main change: adding envtest integration tests for the kube controller.
Linked Issues check	✅ Passed	The PR matches #2486 by adding envtest-based integration tests, starting with the kube controller as requested.
Out of Scope Changes check	✅ Passed	The dependency, Makefile, and README updates support the envtest integration test work and are in scope.

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[coderabbitai]

Actionable comments posted: 5

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: b474ac35-816d-4f5e-bd02-4f19abb97778

📥 Commits

Reviewing files that changed from the base of the PR and between 6f4f2b3 and 313002e.

⛔ Files ignored due to path filters (1)

• go.sum is excluded by !**/*.sum

📒 Files selected for processing (7)

• go.mod
• tests/Makefile
• tests/integration/README.md
• tests/integration/kube/controller/helpers_test.go
• tests/integration/kube/controller/listener_test.go
• tests/integration/kube/controller/site_test.go
• tests/integration/kube/controller/suite_test.go

[ajssmith]

will need to rebase once #2507 is merged

[c-kruse]

Looks good to me!

[c-kruse]

Suggest we add -count=1 to disable test caching. If I run this today make test-integration; make test-integration ENVTEST_K8S_VERSION=1.30.0 the go tests only runs once (assuming it passes a first time).

Also -short does nothing right now, although it could be interesting to have short and long timeouts for local vs CI or something. I could go either way on enabling -race detection.

[ajssmith]

This looks good to me, thanks.

A suggestion would be to document in the README the USE_EXISTING_CLUSTER env var that can run the integration test against full cluster.