test(kubernetes): add WatchTargets test for kubeconfig changes

pkg/kubernetes/provider_watch_test.go

@@ -0,0 +1,95 @@
+package kubernetes
+
+import (
+	"os"
+	"reflect"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/containers/kubernetes-mcp-server/internal/test"
+	"github.com/containers/kubernetes-mcp-server/pkg/config"
+	"github.com/stretchr/testify/suite"
+)
+
+type ProviderWatchTargetsTestSuite struct {
+	suite.Suite
+	mockServer *test.MockServer
+}
+
+func (s *ProviderWatchTargetsTestSuite) SetupTest() {
+	s.mockServer = test.NewMockServer()
+
+	s.T().Setenv("CLUSTER_STATE_POLL_INTERVAL_MS", "100")
+	s.T().Setenv("CLUSTER_STATE_DEBOUNCE_WINDOW_MS", "50")
+}
+
+func (s *ProviderWatchTargetsTestSuite) TearDownTest() {
+	s.mockServer.Close()
+}
+
+// WaitForWatchTargets sets up a WatchTargets callback, executes the provided function, and waits for the callback to be invoked.
+func (s *ProviderWatchTargetsTestSuite) WaitForWatchTargets(timeout time.Duration, provider Provider, fn func()) {
+	callbackInvoked := make(chan struct{})
+	var once sync.Once
+	provider.WatchTargets(func() error {
+		once.Do(func() {
+			close(callbackInvoked)
+		})
+		return nil
+	})
+	fn()
+	select {
+	case <-callbackInvoked:
+		// Callback was invoked
+	case <-time.After(timeout):
+		s.Fail("Timeout waiting for callback to be invoked")
+	}
+}
+
+// WriteKubeconfig appends a newline to the kubeconfig file to trigger the file watcher.
+func (s *ProviderWatchTargetsTestSuite) WriteKubeconfig(k *Kubernetes) {
+	f, err := os.OpenFile(k.ToRawKubeConfigLoader().ConfigAccess().GetExplicitFile(), os.O_APPEND|os.O_WRONLY, 0644)
+	s.Require().NoError(err, "Expected no error opening kubeconfig file")
+	_, err = f.WriteString("\n")
+	s.Require().NoError(err, "Expected no error writing to kubeconfig file")
+	s.Require().NoError(f.Close(), "Expected no error closing kubeconfig file")
+}
+
+func (s *ProviderWatchTargetsTestSuite) TestKubeconfigCacheInvalidation() {
+	s.mockServer.Handle(&test.DiscoveryClientHandler{})
+	staticConfig := &config.StaticConfig{KubeConfig: test.KubeconfigFile(s.T(), s.mockServer.Kubeconfig())}
+
+	testCases := []func() (Provider, error){
+		func() (Provider, error) { return newKubeConfigClusterProvider(staticConfig) },
+		func() (Provider, error) {
+			return newSingleClusterProvider(config.ClusterProviderDisabled)(staticConfig)
+		},
+	}
+	for _, tc := range testCases {
+		provider, err := tc()
+		s.Require().NoError(err, "Expected no error from provider creation")
+
+		s.Run("With provider "+reflect.TypeOf(provider).String(), func() {
+			k, err := provider.GetDerivedKubernetes(s.T().Context(), provider.GetDefaultTarget())
+			s.Require().NoError(err, "Expected no error from GetDerivedKubernetes")
+
+			s.Run("given a fresh cache", func() {
+				_, err := k.AccessControlClientset().DiscoveryClient().ServerGroups()
+				s.Require().NoError(err, "Expected no error from AccessControlClientset")
+				s.Require().True(k.AccessControlClientset().DiscoveryClient().Fresh())
+			})
+
+			s.Run("invalidates caches (fresh==false) when kubeconfig is changed", func() {
+				s.WaitForWatchTargets(5*time.Second, provider, func() {
+					s.WriteKubeconfig(k)
+				})
+				s.Require().False(k.AccessControlClientset().DiscoveryClient().Fresh())
+			})
+		})
+	}
+}
+
+func TestProviderWatchTargetsTestSuite(t *testing.T) {
+	suite.Run(t, new(ProviderWatchTargetsTestSuite))
+}