multiflag: add simple testcases

Signed-off-by: Mustafa Abdelrahman <mustafa.abdelrahman@zalando.de>

Author: MustafaSaber

config/config_test.go

@@ -14,7 +14,6 @@ import (
 	"github.com/zalando/skipper/filters/openpolicyagent"
 	"github.com/zalando/skipper/net"
 	"github.com/zalando/skipper/proxy"
-	"gopkg.in/yaml.v2"
 
 	"github.com/google/go-cmp/cmp"
 	"github.com/google/go-cmp/cmp/cmpopts"
@@ -482,11 +481,3 @@ func TestDeprecatedFlags(t *testing.T) {
 		}
 	}
 }
-
-func TestMultiFlagYamlErr(t *testing.T) {
-	m := &multiFlag{}
-	err := yaml.Unmarshal([]byte(`foo=bar`), m)
-	if err == nil {
-		t.Error("Failed to get error on wrong yaml input")
-	}
-}

config/multiflag_test.go

@@ -0,0 +1,41 @@
+package config
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"gopkg.in/yaml.v2"
+)
+
+func TestMultiFlagSet(t *testing.T) {
+	for _, tc := range []struct {
+		name   string
+		args   string
+		values string
+	}{
+		{
+			name:   "single value",
+			args:   "foo=bar",
+			values: "foo=bar",
+		},
+		{
+			name:   "multiple values",
+			args:   "foo=bar foo=baz foo=qux bar=baz",
+			values: "foo=bar foo=baz foo=qux bar=baz",
+		},
+	} {
+		t.Run(tc.name+"_valid", func(t *testing.T) {
+			multiFlag := &multiFlag{}
+			err := multiFlag.Set(tc.args)
+			require.NoError(t, err)
+			assert.Equal(t, tc.values, multiFlag.String())
+		})
+	}
+}
+
+func TestMultiFlagYamlErr(t *testing.T) {
+	m := &multiFlag{}
+	err := yaml.Unmarshal([]byte(`-foo=bar`), m)
+	require.Error(t, err, "Failed to get error on wrong yaml input")
+}