kubeadm: Add testcases for exported method ValueFromFlagsOrConfig

Signed-off-by: Dave Chen <dave.chen@arm.com>

cmd/kubeadm/app/cmd/util/cmdutil_test.go

@@ -17,8 +17,10 @@ limitations under the License.
 package util
 
 import (
+	"fmt"
 	"testing"
 
+	"github.com/spf13/pflag"
 	"k8s.io/client-go/tools/clientcmd"
 )
 
@@ -103,3 +105,53 @@ func TestGetKubeConfigPath(t *testing.T) {
 		})
 	}
 }
+
+func TestValueFromFlagsOrConfig(t *testing.T) {
+	var tests = []struct {
+		name      string
+		flag      string
+		cfg       interface{}
+		flagValue interface{}
+		expected  interface{}
+	}{
+		{
+			name:      "string: config is overridden by the flag",
+			flag:      "foo",
+			cfg:       "foo_cfg",
+			flagValue: "foo_flag",
+			expected:  "foo_flag",
+		},
+		{
+			name:      "bool: config is overridden by the flag",
+			flag:      "bar",
+			cfg:       true,
+			flagValue: false,
+			expected:  false,
+		},
+	}
+	for _, tt := range tests {
+		type options struct {
+			foo string
+			bar bool
+		}
+		fakeOptions := &options{}
+		fs := pflag.FlagSet{}
+		fs.StringVar(&fakeOptions.foo, "foo", "", "")
+		fs.BoolVar(&fakeOptions.bar, "bar", false, "")
+
+		t.Run(tt.name, func(t *testing.T) {
+			err := fs.Set(tt.flag, fmt.Sprintf("%v", tt.flagValue))
+			if err != nil {
+				t.Fatalf("failed to set the value of the flag %v", tt.flagValue)
+			}
+			actualResult := ValueFromFlagsOrConfig(&fs, tt.flag, tt.cfg, tt.flagValue)
+			if actualResult != tt.expected {
+				t.Errorf(
+					"failed ValueFromFlagsOrConfig:\n\texpected: %s\n\t  actual: %s",
+					tt.expected,
+					actualResult,
+				)
+			}
+		})
+	}
+}