test: add unit tests for runCmd and fix typo in package doc

browser.go

@@ -1,6 +1,6 @@
 // Package browser provides helpers to open files, readers, and urls in a browser window.
 //
-// The choice of which browser is started is entirely client dependant.
+// The choice of which browser is started is entirely client dependent.
 package browser
 
 import (

browser_test.go

@@ -0,0 +1,33 @@
+package browser
+
+import (
+	"bytes"
+	"os"
+	"strings"
+	"testing"
+)
+
+func TestRunCmd(t *testing.T) {
+	var stdout, stderr bytes.Buffer
+	Stdout = &stdout
+	Stderr = &stderr
+	defer func() {
+		Stdout = os.Stdout
+		Stderr = os.Stderr
+	}()
+
+	err := runCmd("echo", "hello", "world")
+	if err != nil {
+		t.Fatalf("runCmd failed: %v", err)
+	}
+	if !strings.Contains(stdout.String(), "hello world") {
+		t.Errorf("stdout = %q, expected to contain %q", stdout.String(), "hello world")
+	}
+}
+
+func TestRunCmdError(t *testing.T) {
+	err := runCmd("nonexistent-command-xyz-12345")
+	if err == nil {
+		t.Error("expected error for nonexistent command, got nil")
+	}
+}