fix when adding only one capability (zalando#1339)

* fix when adding only one capability

* fix error messages in unit test

Author: FxKu

pkg/cluster/k8sres.go

@@ -321,7 +321,7 @@ func getLocalAndBoostrapPostgreSQLParameters(parameters map[string]string) (loca
 }
 
 func generateCapabilities(capabilities []string) v1.Capabilities {
-	if len(capabilities) > 1 {
+	if len(capabilities) > 0 {
 		additionalCapabilities := []v1.Capability{}
 		for _, capability := range capabilities {
 			additionalCapabilities = append(additionalCapabilities, v1.Capability(strings.ToUpper(capability)))

pkg/cluster/k8sres_test.go

@@ -1511,13 +1511,21 @@ func TestGenerateCapabilities(t *testing.T) {
 			capabilities: v1.Capabilities{},
 			err:          fmt.Errorf("could not parse empty capabilities configuration"),
 		},
+		{
+			subTest:    "configured capability",
+			configured: []string{"SYS_NICE"},
+			capabilities: v1.Capabilities{
+				Add: []v1.Capability{"SYS_NICE"},
+			},
+			err: fmt.Errorf("could not generate one configured capability"),
+		},
 		{
 			subTest:    "configured capabilities",
 			configured: []string{"SYS_NICE", "CHOWN"},
 			capabilities: v1.Capabilities{
 				Add: []v1.Capability{"SYS_NICE", "CHOWN"},
 			},
-			err: fmt.Errorf("could not parse empty capabilities configuration"),
+			err: fmt.Errorf("could not generate multiple configured capabilities"),
 		},
 	}
 	for _, tt := range tests {