diff --git a/README.md b/README.md
index ecdf0b9..112fd77 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![PkgGoDev](https://pkg.go.dev/badge/image)](https://pkg.go.dev/github.com/ncruces/zenity)
 [![Go Report](https://goreportcard.com/badge/github.com/ncruces/zenity)](https://goreportcard.com/report/github.com/ncruces/zenity)
-[![Go Report](http://gocover.io/_badge/github.com/ncruces/zenity)](https://gocover.io/github.com/ncruces/zenity)
+[![Go Report](https://gocover.io/_badge/github.com/ncruces/zenity)](https://gocover.io/github.com/ncruces/zenity)
 
 This repo includes both a cross-platform Go package providing
 [Zenity](https://help.gnome.org/users/zenity/stable/)-like dialogs
diff --git a/util_unix_test.go b/util_unix_test.go
new file mode 100644
index 0000000..4d7bc5d
--- /dev/null
+++ b/util_unix_test.go
@@ -0,0 +1,113 @@
+// +build !windows
+
+package zenity
+
+import (
+	"errors"
+	"os/exec"
+	"reflect"
+	"testing"
+
+	"github.com/ncruces/zenity/internal/zenutil"
+)
+
+func Test_appendTitle(t *testing.T) {
+	got := appendTitle(nil, options{title: stringPtr("Title")})
+	want := []string{"--title", "Title"}
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("appendTitle() = %v, want %v", got, want)
+	}
+}
+
+func Test_appendButtons(t *testing.T) {
+	tests := []struct {
+		name string
+		opts options
+		want []string
+	}{
+		{name: "OK", opts: options{okLabel: stringPtr("OK")}, want: []string{"--ok-label", "OK"}},
+		{name: "Cancel", opts: options{cancelLabel: stringPtr("Cancel")}, want: []string{"--cancel-label", "Cancel"}},
+		{name: "Extra", opts: options{extraButton: stringPtr("Extra")}, want: []string{"--extra-button", "Extra"}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := appendButtons(nil, tt.opts); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("appendButtons() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_appendWidthHeight(t *testing.T) {
+	tests := []struct {
+		name string
+		opts options
+		want []string
+	}{
+		{name: "Width", opts: options{width: 100}, want: []string{"--width", "100"}},
+		{name: "Height", opts: options{height: 100}, want: []string{"--height", "100"}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := appendWidthHeight(nil, tt.opts); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("appendWidthHeight() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_appendIcon(t *testing.T) {
+	tests := []struct {
+		name string
+		opts options
+		want []string
+	}{
+		{name: "NoIcon", opts: options{icon: NoIcon}, want: nil},
+		{name: "Info", opts: options{icon: InfoIcon}, want: []string{"--window-icon=info"}},
+		{name: "Error", opts: options{icon: ErrorIcon}, want: []string{"--window-icon=error"}},
+		{name: "Warning", opts: options{icon: WarningIcon}, want: []string{"--window-icon=warning"}},
+		{name: "Question", opts: options{icon: QuestionIcon}, want: []string{"--window-icon=question"}},
+		{name: "Password", opts: options{icon: PasswordIcon}, want: nil},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := appendIcon(nil, tt.opts); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("appendIcon() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_strResult(t *testing.T) {
+	sentinel := errors.New("sentinel")
+	cancel := exec.Command("false").Run()
+
+	if out, err := strResult(options{}, []byte("out"), nil); out != "out" || err != nil {
+		t.Errorf("strResult(out, nil) = %q, %v", out, err)
+	}
+	if out, err := strResult(options{}, []byte("out"), sentinel); out != "" || err != sentinel {
+		t.Errorf("strResult(out, nil) = %q, %v", out, err)
+	}
+	if out, err := strResult(options{}, []byte("out"), cancel); out != "" || err != ErrCanceled {
+		t.Errorf("strResult(out, nil) = %q, %v", out, err)
+	}
+}
+
+func Test_lstResult(t *testing.T) {
+	zenutil.Separator = "|"
+	sentinel := errors.New("sentinel")
+	cancel := exec.Command("false").Run()
+
+	if out, err := lstResult(options{}, []byte("out"), nil); !reflect.DeepEqual(out, []string{"out"}) || err != nil {
+		t.Errorf("lstResult(out, nil) = %v, %v", out, err)
+	}
+	if out, err := lstResult(options{}, []byte("one|two"), nil); !reflect.DeepEqual(out, []string{"one", "two"}) || err != nil {
+		t.Errorf("lstResult(out, nil) = %v, %v", out, err)
+	}
+	if out, err := lstResult(options{}, []byte("out"), sentinel); out != nil || err != sentinel {
+		t.Errorf("lstResult(out, nil) = %v, %v", out, err)
+	}
+	if out, err := lstResult(options{}, []byte("out"), cancel); out != nil || err != ErrCanceled {
+		t.Errorf("lstResult(out, nil) = %q, %v", out, err)
+	}
+}
diff --git a/zenity_test.go b/zenity_test.go
new file mode 100644
index 0000000..56a11f3
--- /dev/null
+++ b/zenity_test.go
@@ -0,0 +1,68 @@
+package zenity
+
+import (
+	"context"
+	"image/color"
+	"reflect"
+	"testing"
+)
+
+func Test_applyOptions(t *testing.T) {
+	tests := []struct {
+		name string
+		args Option
+		want options
+	}{
+		// General options
+		{name: "Title", args: Title("Title"), want: options{title: stringPtr("Title")}},
+		{name: "Width", args: Width(100), want: options{width: 100}},
+		{name: "Height", args: Height(100), want: options{height: 100}},
+		{name: "OKLabel", args: OKLabel("OK"), want: options{okLabel: stringPtr("OK")}},
+		{name: "CancelLabel", args: CancelLabel("Cancel"), want: options{cancelLabel: stringPtr("Cancel")}},
+		{name: "ExtraButton", args: ExtraButton("Extra"), want: options{extraButton: stringPtr("Extra")}},
+		{name: "Icon", args: Icon(ErrorIcon), want: options{icon: ErrorIcon}},
+		{name: "DefaultCancel", args: DefaultCancel(), want: options{defaultCancel: true}},
+
+		// Message options
+		{name: "NoWrap", args: NoWrap(), want: options{noWrap: true}},
+		{name: "Ellipsize", args: Ellipsize(), want: options{ellipsize: true}},
+
+		// Entry options
+		{name: "EntryText", args: EntryText("text"), want: options{entryText: "text"}},
+		{name: "HideText", args: HideText(), want: options{hideText: true}},
+		{name: "Username", args: Username(), want: options{username: true}},
+
+		// List options
+		{name: "DisallowEmpty", args: DisallowEmpty(), want: options{disallowEmpty: true}},
+		{name: "DefaultItems", args: DefaultItems("a", "b"), want: options{defaultItems: []string{"a", "b"}}},
+
+		// File selection options
+		{name: "Directory", args: Directory(), want: options{directory: true}},
+		{name: "ConfirmOverwrite", args: ConfirmOverwrite(), want: options{confirmOverwrite: true}},
+		{name: "ConfirmCreate", args: ConfirmCreate(), want: options{confirmCreate: true}},
+		{name: "ShowHidden", args: ShowHidden(), want: options{showHidden: true}},
+		{name: "Filename", args: Filename("file.go"), want: options{filename: "file.go"}},
+		{name: "FileFilters", args: FileFilter{"Go files", []string{"*.go"}}, want: options{
+			fileFilters: FileFilters{{"Go files", []string{"*.go"}}},
+		}},
+
+		// Progress indication options
+		{name: "MaxValue", args: MaxValue(100), want: options{maxValue: 100}},
+		{name: "NoCancel", args: NoCancel(), want: options{noCancel: true}},
+		{name: "TimeRemaining", args: TimeRemaining(), want: options{timeRemaining: true}},
+
+		// Color selection options
+		{name: "Color", args: Color(color.Black), want: options{color: color.Black}},
+		{name: "ShowPalette", args: ShowPalette(), want: options{showPalette: true}},
+
+		// Context for timeout
+		{name: "Context", args: Context(context.TODO()), want: options{ctx: context.TODO()}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := applyOptions([]Option{tt.args}); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("applyOptions() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}