Minor refactoring, add tests.

Address the code review by Sergey.

pkg/cluster/cluster.go

@@ -620,7 +620,7 @@ func (c *Cluster) initRobotUsers() error {
 			return fmt.Errorf("invalid username: %q", username)
 		}
 
-		if c.avoidProtectedOrSystemRole(username, "manifest robot role") {
+		if c.shouldAvoidProtectedOrSystemRole(username, "manifest robot role") {
 			continue
 		}
 		flags, err := normalizeUserFlags(userFlags)
@@ -656,7 +656,7 @@ func (c *Cluster) initHumanUsers() error {
 		flags := []string{constants.RoleFlagLogin}
 		memberOf := []string{c.OpConfig.PamRoleName}
 
-		if c.avoidProtectedOrSystemRole(username, "API role") {
+		if c.shouldAvoidProtectedOrSystemRole(username, "API role") {
 			continue
 		}
 		if c.OpConfig.EnableTeamSuperuser {
@@ -688,7 +688,7 @@ func (c *Cluster) initInfrastructureRoles() error {
 		if !isValidUsername(username) {
 			return fmt.Errorf("invalid username: '%v'", username)
 		}
-		if c.avoidProtectedOrSystemRole(username, "infrastructure role") {
+		if c.shouldAvoidProtectedOrSystemRole(username, "infrastructure role") {
 			continue
 		}
 		flags, err := normalizeUserFlags(data.Flags)
@@ -701,7 +701,7 @@ func (c *Cluster) initInfrastructureRoles() error {
 	return nil
 }
 
-func (c *Cluster) avoidProtectedOrSystemRole(username, purpose string) bool {
+func (c *Cluster) shouldAvoidProtectedOrSystemRole(username, purpose string) bool {
 	if c.isProtectedUsername(username) {
 		c.logger.Warnf("cannot initialize a new %s with the name of the protected user %q", purpose, username)
 		return true

pkg/cluster/cluster_test.go

@@ -4,14 +4,18 @@ import (
 	"fmt"
 	"github.com/Sirupsen/logrus"
 	"github.com/zalando-incubator/postgres-operator/pkg/spec"
+	"github.com/zalando-incubator/postgres-operator/pkg/util/config"
 	"github.com/zalando-incubator/postgres-operator/pkg/util/k8sutil"
 	"github.com/zalando-incubator/postgres-operator/pkg/util/teams"
 	"reflect"
 	"testing"
 )
 
 var logger = logrus.New().WithField("test", "cluster")
-var cl = New(Config{}, k8sutil.KubernetesClient{}, spec.Postgresql{}, logger)
+var cl = New(Config{OpConfig: config.Config{ProtectedRoles: []string{"admin"},
+	Auth: config.Auth{SuperUsername: "postgres",
+		ReplicationUsername: "standby"}}},
+	k8sutil.KubernetesClient{}, spec.Postgresql{}, logger)
 
 func TestInitRobotUsers(t *testing.T) {
 	testName := "TestInitRobotUsers"
@@ -47,6 +51,12 @@ func TestInitRobotUsers(t *testing.T) {
 			err: fmt.Errorf(`invalid flags for user "foobar": ` +
 				`conflicting user flags: "NOINHERIT" and "INHERIT"`),
 		},
+		{
+			manifestUsers: map[string]spec.UserFlags{"admin": {"superuser"}, "postgres": {"createdb"}},
+			infraRoles:    map[string]spec.PgUser{},
+			result:        map[string]spec.PgUser{},
+			err:           nil,
+		},
 	}
 	for _, tt := range tests {
 		cl.Spec.Users = tt.manifestUsers
@@ -109,6 +119,11 @@ func TestInitHumanUsers(t *testing.T) {
 			result: map[string]spec.PgUser{"foo": {Name: "foo", MemberOf: []string{cl.OpConfig.PamRoleName}, Flags: []string{"LOGIN", "SUPERUSER"}},
 				"bar": {Name: "bar", Flags: []string{"NOLOGIN"}}},
 		},
+		{
+			existingRoles: map[string]spec.PgUser{},
+			teamRoles:     []string{"admin", "standby"},
+			result:        map[string]spec.PgUser{},
+		},
 	}
 
 	for _, tt := range tests {