test: use build tags for e2e tests, remove ErrSkip pattern

Add //go:build e2e to all e2e test files and the framework so that
go test ./... works locally without a cluster. CI runs e2e via
make test-e2e which passes -tags e2e.

Replace the ErrSkip sentinel with direct error returns from
framework.New() — the build tag is the exclusion mechanism, not
runtime skips. Tests now t.Fatal immediately if KUBECONFIG or
PLUGIN_URL are unset when compiled with the e2e tag.

Also adds a unit-test Makefile alias (delegates to test-backend)
for clarity.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: sradco

Makefile

@@ -58,13 +58,15 @@ build-backend:
 start-backend:
 	go run ./cmd/plugin-backend.go -port='9001' -config-path='./config' -static-path='./web/dist'
 
-.PHONY: test-backend
+.PHONY: unit-test test-backend
+unit-test: test-backend
+
 test-backend:
 	go test ./pkg/... ./internal/... -v
 
 .PHONY: test-e2e
 test-e2e:
-	go test -v -timeout=150m -count=1 ./test/e2e
+	go test -tags e2e -v -timeout=150m -count=1 ./test/e2e
 
 .PHONY: test-frontend
 test-frontend:

test/e2e/create_alert_rule_test.go

@@ -1,8 +1,9 @@
+//go:build e2e
+
 package e2e
 
 import (
 	"context"
-	"errors"
 	"testing"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -13,9 +14,6 @@ import (
 
 func TestCreateUserDefinedAlertRule(t *testing.T) {
 	f, err := framework.New()
-	if errors.Is(err, framework.ErrSkip) {
-		t.Skip(err)
-	}
 	if err != nil {
 		t.Fatalf("Failed to create framework: %v", err)
 	}

test/e2e/delete_alert_rule_test.go

@@ -1,10 +1,11 @@
+//go:build e2e
+
 package e2e
 
 import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
 	"net/http"
@@ -19,9 +20,6 @@ import (
 
 func TestDeleteAlertRule(t *testing.T) {
 	f, err := framework.New()
-	if errors.Is(err, framework.ErrSkip) {
-		t.Skip(err)
-	}
 	if err != nil {
 		t.Fatalf("Failed to create framework: %v", err)
 	}
@@ -38,10 +36,6 @@ func TestDeleteAlertRule(t *testing.T) {
 	ruleIDs := make([]string, 0, len(ruleNames))
 
 	for _, name := range ruleNames {
-		// Each rule needs a unique expression so the spec-equivalence check
-		// does not reject it as a duplicate of a rule from another test.
-		// absent() returns 1 when the selector matches nothing, which is
-		// always the case for a fabricated metric name.
 		expr := fmt.Sprintf("absent(nonexistent{e2e_rule=%q})", name)
 		id, err := createRuleViaAPI(ctx, f, managementrouter.CreateAlertRuleRequest{
 			AlertingRule: &managementrouter.AlertRuleSpec{
@@ -65,8 +59,6 @@ func TestDeleteAlertRule(t *testing.T) {
 
 	t.Logf("Created 3 rules with IDs: %v", ruleIDs)
 
-	// Allow time for the informer watch event to propagate and
-	// the relabeled-rules cache to sync the new PrometheusRule.
 	time.Sleep(2 * time.Second)
 
 	deleteReq := managementrouter.BulkDeleteAlertRulesRequest{

test/e2e/framework/framework.go

@@ -1,3 +1,5 @@
+//go:build e2e
+
 package framework
 
 import (
@@ -38,23 +40,22 @@ type Framework struct {
 
 type CleanupFunc func() error
 
-// ErrSkip is returned by New when required environment variables are not set,
-// so callers can distinguish a missing-env skip from a real error.
-var ErrSkip = fmt.Errorf("required environment variables not set, skipping e2e test")
-
+// New creates a Framework backed by a real Kubernetes cluster. It reads
+// KUBECONFIG and PLUGIN_URL from the environment and returns a singleton
+// so that expensive client setup happens only once per test binary.
 func New() (*Framework, error) {
 	if f != nil {
 		return f, nil
 	}
 
 	kubeConfigPath := os.Getenv("KUBECONFIG")
 	if kubeConfigPath == "" {
-		return nil, fmt.Errorf("%w: KUBECONFIG", ErrSkip)
+		return nil, fmt.Errorf("KUBECONFIG environment variable is not set")
 	}
 
 	pluginURL := os.Getenv("PLUGIN_URL")
 	if pluginURL == "" {
-		return nil, fmt.Errorf("%w: PLUGIN_URL", ErrSkip)
+		return nil, fmt.Errorf("PLUGIN_URL environment variable is not set")
 	}
 
 	config, err := clientcmd.BuildConfigFromFlags("", kubeConfigPath)

test/e2e/helpers_test.go

@@ -1,3 +1,5 @@
+//go:build e2e
+
 package e2e
 
 import (