test: Address globals pollution in metrics tests

Make all globals reset states during and after tests that manipulate
them.

Signed-off-by: Pranshu Srivastava <rexagod@gmail.com>

staging/src/k8s.io/component-base/metrics/options_test.go

@@ -28,6 +28,8 @@ import (
 )
 
 func TestEnableHiddenMetrics(t *testing.T) {
+	resetMetricsGlobalState(t)
+
 	currentVersion := apimachineryversion.Info{
 		Major:      "1",
 		Minor:      "17",
@@ -198,6 +200,8 @@ func TestEnableHiddenStableCollector(t *testing.T) {
 }
 
 func TestShowHiddenMetric(t *testing.T) {
+	resetMetricsGlobalState(t)
+
 	registry := newKubeRegistry(apimachineryversion.Info{
 		Major:      "1",
 		Minor:      "15",
@@ -212,7 +216,6 @@ func TestShowHiddenMetric(t *testing.T) {
 	assert.Lenf(t, ms, expectedMetricCount, "Got %v metrics, Want: %v metrics", len(ms), expectedMetricCount)
 
 	showHidden.Store(true)
-	defer showHidden.Store(false)
 	registry.MustRegister(NewCounter(
 		&CounterOpts{
 			Namespace:         "some_namespace",
@@ -231,6 +234,8 @@ func TestShowHiddenMetric(t *testing.T) {
 }
 
 func TestDisabledMetrics(t *testing.T) {
+	resetMetricsGlobalState(t)
+
 	o := NewOptions()
 	o.DisabledMetrics = []string{"should_be_disabled", "should_be_disabled"} // should be deduplicated (disabled_metrics_total == 1)
 	currentVersion := apimachineryversion.Info{

staging/src/k8s.io/component-base/metrics/registry_test.go

@@ -18,6 +18,7 @@ package metrics
 
 import (
 	"strings"
+	"sync"
 	"testing"
 
 	"github.com/blang/semver/v4"
@@ -27,6 +28,33 @@ import (
 	apimachineryversion "k8s.io/apimachinery/pkg/version"
 )
 
+// resetMetricsGlobalState resets all global state used by metrics tests.
+// NOTE: This should be called at the start of tests and in cleanup to ensure test isolation.
+func resetMetricsGlobalState(t *testing.T) {
+	resetter := func() {
+		hiddenMetricsTotal.Reset()
+		disabledMetricsTotal.Reset()
+
+		showHidden.Store(false)
+		showHiddenOnce = sync.Once{}
+
+		alphaCounter.ClearState()
+		alphaDeprecatedCounter.ClearState()
+		betaDeprecatedCounter.ClearState()
+		alphaHiddenCounter.ClearState()
+
+		disabledMetricsLock.Lock()
+		disabledMetrics = map[string]struct{}{}
+		disabledMetricsLock.Unlock()
+	}
+
+	// Reset at the start of tests
+	resetter()
+
+	// Register cleanup to reset again after test completes
+	t.Cleanup(resetter)
+}
+
 var (
 	v115         = semver.MustParse("1.15.0")
 	alphaCounter = NewCounter(
@@ -265,6 +293,8 @@ func TestShouldHide(t *testing.T) {
 }
 
 func TestRegister(t *testing.T) {
+	resetMetricsGlobalState(t)
+
 	var tests = []struct {
 		desc                    string
 		metrics                 []*Counter
@@ -334,6 +364,8 @@ func TestRegister(t *testing.T) {
 }
 
 func TestMustRegister(t *testing.T) {
+	resetMetricsGlobalState(t)
+
 	var tests = []struct {
 		desc            string
 		metrics         []*Counter