@@ -0,0 +1,31 @@
+package attr_test
+
+import (
+	"testing"
+
+	"github.com/maragudk/gomponents/assert"
+	"github.com/maragudk/gomponents/attr"
+)
+
+func TestID(t *testing.T) {
+	t.Run("given a value, returns id=value", func(t *testing.T) {
+		assert.Equal(t, ` id="hat"`, attr.ID("hat"))
+	})
+}
+
+func TestClass(t *testing.T) {
+	t.Run("given a value, returns class=value", func(t *testing.T) {
+		assert.Equal(t, ` class="hat"`, attr.Class("hat"))
+	})
+}
+
+func TestClasses(t *testing.T) {
+	t.Run("given a map, returns sorted keys from the map with value true", func(t *testing.T) {
+		assert.Equal(t, ` class="boheme-hat hat partyhat"`, attr.Classes(map[string]bool{
+			"boheme-hat": true,
+			"hat":        true,
+			"partyhat":   true,
+			"turtlehat":  false,
+		}))
+	})
+}