diff --git a/go/flagutil/flagutil_test.go b/go/flagutil/flagutil_test.go
index 2502213ab73..1ddbf693e27 100644
--- a/go/flagutil/flagutil_test.go
+++ b/go/flagutil/flagutil_test.go
@@ -35,10 +35,9 @@ func TestStringList(t *testing.T) {
 		"3ala,":          "3ala.",
 	}
 	for in, out := range wanted {
-		if err := p.Set(in); err != nil {
-			t.Errorf("v.Set(%v): %v", in, err)
-			continue
-		}
+		err := p.Set(in)
+		assert.NoError(t, err)
+
 		assert.Equal(t, out, strings.Join(p, "."))
 		assert.Equal(t, in, p.String())
 
@@ -49,12 +48,10 @@ func TestStringList(t *testing.T) {
 func TestEmptyStringList(t *testing.T) {
 	var p StringListValue
 	var _ pflag.Value = &p
-	if err := p.Set(""); err != nil {
-		t.Fatalf("p.Set(\"\"): %v", err)
-	}
-	if len(p) != 0 {
-		t.Fatalf("len(p) != 0: got %v", len(p))
-	}
+
+	err := p.Set("")
+	require.NoError(t, err)
+	require.Len(t, p, 0)
 }
 
 type pair struct {
@@ -81,28 +78,15 @@ func TestStringMap(t *testing.T) {
 		},
 	}
 	for _, want := range wanted {
-		if err := v.Set(want.in); err != want.err {
-			t.Errorf("v.Set(%v): %v", want.in, want.err)
-			continue
-		}
-		if want.err != nil {
-			continue
-		}
+		err := v.Set(want.in)
+		assert.ErrorIs(t, err, want.err)
 
-		if len(want.out) != len(v) {
-			t.Errorf("want %#v, got %#v", want.out, v)
+		if want.err != nil {
 			continue
 		}
-		for key, value := range want.out {
-			if v[key] != value {
-				t.Errorf("want %#v, got %#v", want.out, v)
-				continue
-			}
-		}
 
-		if vs := v.String(); vs != want.in {
-			t.Errorf("v.String(): want %#v, got %#v", want.in, vs)
-		}
+		assert.EqualValues(t, want.out, v)
+		assert.Equal(t, want.in, v.String())
 	}
 }
 
@@ -119,3 +103,179 @@ func TestStringMapValue(t *testing.T) {
 	require.Equal(t, "StringMap", strMapVal.Type())
 	require.Equal(t, map[string]string(map[string]string{"key": "val"}), strMapVal.Get())
 }
+
+func TestDualFormatStringListVar(t *testing.T) {
+	testFlagSet := pflag.NewFlagSet("testFlagSet", pflag.ExitOnError)
+
+	testFlagName := "test-flag_name"
+	var flagVal []string
+	testValue := []string{"testValue1", "testValue2", "testValue3"}
+
+	DualFormatStringListVar(testFlagSet, &flagVal, testFlagName, testValue, "usage string")
+	assert.Equal(t, testValue, flagVal)
+
+	want := "testValue1,testValue2,testValue3"
+	f := testFlagSet.Lookup("test-flag-name")
+	assert.NotNil(t, f)
+	assert.Equal(t, want, f.Value.String())
+
+	f = testFlagSet.Lookup("test_flag_name")
+	assert.NotNil(t, f)
+	assert.Equal(t, want, f.Value.String())
+
+	newVal := "newValue1,newValue2"
+	err := testFlagSet.Set("test-flag-name", newVal)
+	assert.NoError(t, err)
+
+	assert.Equal(t, newVal, f.Value.String())
+	assert.Equal(t, []string{"newValue1", "newValue2"}, flagVal)
+}
+
+func TestDualFormatStringVar(t *testing.T) {
+	testFlagSet := pflag.NewFlagSet("testFlagSet", pflag.ExitOnError)
+
+	testFlagName := "test-flag_name"
+	var flagVal string
+	testValue := "testValue"
+
+	DualFormatStringVar(testFlagSet, &flagVal, testFlagName, testValue, "usage string")
+	assert.Equal(t, testValue, flagVal)
+
+	f := testFlagSet.Lookup("test-flag-name")
+	assert.NotNil(t, f)
+	assert.Equal(t, testValue, f.Value.String())
+
+	f = testFlagSet.Lookup("test_flag_name")
+	assert.NotNil(t, f)
+	assert.Equal(t, testValue, f.Value.String())
+
+	newVal := "newValue"
+	err := testFlagSet.Set("test-flag-name", newVal)
+	assert.NoError(t, err)
+
+	assert.Equal(t, newVal, f.Value.String())
+	assert.Equal(t, newVal, flagVal)
+}
+
+func TestDualFormatBoolVar(t *testing.T) {
+	testFlagSet := pflag.NewFlagSet("testFlagSet", pflag.ExitOnError)
+
+	testFlagName := "test-flag_name"
+	var flagVal bool
+
+	DualFormatBoolVar(testFlagSet, &flagVal, testFlagName, true, "usage string")
+	assert.True(t, flagVal)
+
+	f := testFlagSet.Lookup("test-flag-name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "true", f.Value.String())
+
+	f = testFlagSet.Lookup("test_flag_name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "true", f.Value.String())
+
+	err := testFlagSet.Set("test-flag-name", "false")
+	assert.NoError(t, err)
+
+	assert.Equal(t, "false", f.Value.String())
+	assert.False(t, flagVal)
+}
+
+func TestDualFormatInt64Var(t *testing.T) {
+	testFlagSet := pflag.NewFlagSet("testFlagSet", pflag.ExitOnError)
+
+	testFlagName := "test-flag_name"
+	var flagVal int64
+
+	DualFormatInt64Var(testFlagSet, &flagVal, testFlagName, int64(256), "usage string")
+	assert.Equal(t, int64(256), flagVal)
+
+	f := testFlagSet.Lookup("test-flag-name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "256", f.Value.String())
+
+	f = testFlagSet.Lookup("test_flag_name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "256", f.Value.String())
+
+	newVal := "128"
+	err := testFlagSet.Set("test-flag-name", newVal)
+	assert.NoError(t, err)
+
+	assert.Equal(t, newVal, f.Value.String())
+	assert.Equal(t, int64(128), flagVal)
+}
+
+func TestDualFormatIntVar(t *testing.T) {
+	testFlagSet := pflag.NewFlagSet("testFlagSet", pflag.ExitOnError)
+
+	testFlagName := "test-flag_name"
+	var flagVal int
+
+	DualFormatIntVar(testFlagSet, &flagVal, testFlagName, 128, "usage string")
+	assert.Equal(t, 128, flagVal)
+
+	f := testFlagSet.Lookup("test-flag-name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "128", f.Value.String())
+
+	f = testFlagSet.Lookup("test_flag_name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "128", f.Value.String())
+
+	newVal := "256"
+	err := testFlagSet.Set("test-flag-name", newVal)
+	assert.NoError(t, err)
+
+	assert.Equal(t, newVal, f.Value.String())
+	assert.Equal(t, 256, flagVal)
+}
+
+type MockValue struct {
+	val *bool
+}
+
+func (b MockValue) Set(s string) error {
+	if s == "true" {
+		*b.val = true
+	} else {
+		*b.val = false
+	}
+	return nil
+}
+
+func (b MockValue) String() string {
+	if *b.val {
+		return "true"
+	}
+	return "false"
+}
+
+func (b MockValue) Type() string {
+	return "bool"
+}
+
+func TestDualFormatVar(t *testing.T) {
+	testFlagSet := pflag.NewFlagSet("testFlagSet", pflag.ExitOnError)
+
+	testFlagName := "test-flag_name"
+	flagVal := true
+	value := MockValue{val: &flagVal}
+
+	DualFormatVar(testFlagSet, value, testFlagName, "usage string")
+
+	f := testFlagSet.Lookup("test-flag-name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "true", f.Value.String())
+
+	f = testFlagSet.Lookup("test_flag_name")
+	assert.NotNil(t, f)
+	assert.Equal(t, "true", f.Value.String())
+
+	newVal := "false"
+	err := testFlagSet.Set("test-flag-name", newVal)
+	assert.NoError(t, err)
+
+	assert.Equal(t, newVal, f.Value.String())
+	assert.False(t, flagVal)
+}