diff --git a/kbuilder/kbuilder.go b/kbuilder/kbuilder.go
index 78998d4..b17b808 100644
--- a/kbuilder/kbuilder.go
+++ b/kbuilder/kbuilder.go
@@ -67,7 +67,9 @@ func (builder *Builder) Build(query Query) (sqlQuery string, params []interface{
 }
 
 type Query struct {
-	// Select expects a struct using the `ksql` tags
+	// Select expects either a struct using the `ksql` tags
+	// or a string listing the column names using SQL syntax,
+	// e.g.: `id, username, address`
 	Select interface{}
 
 	// From expects the FROM clause from an SQL query, e.g. `users JOIN posts USING(post_id)`
diff --git a/kbuilder/kbuilder_test.go b/kbuilder/kbuilder_test.go
index 23623b0..bbf4503 100644
--- a/kbuilder/kbuilder_test.go
+++ b/kbuilder/kbuilder_test.go
@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"testing"
 
+	"github.com/stretchr/testify/require"
 	"github.com/tj/assert"
 	"github.com/vingarcia/ksql/kbuilder"
 )
@@ -137,8 +138,8 @@ func TestBuilder(t *testing.T) {
 
 func expectError(t *testing.T, expect bool, err error) {
 	if expect {
-		assert.Equal(t, true, err != nil, "expected an error, but got nothing")
+		require.Equal(t, true, err != nil, "expected an error, but got nothing")
 	} else {
-		assert.Equal(t, false, err != nil, fmt.Sprintf("unexpected error %s", err))
+		require.Equal(t, false, err != nil, fmt.Sprintf("unexpected error %s", err))
 	}
 }