add test append fields

field/fields_test.go

@@ -0,0 +1,15 @@
+package field_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	"gitoa.ru/go-4devs/log/field"
+)
+
+func TestFields_Append(t *testing.T) {
+	fields := field.Fields{field.Any("any", "value")}
+	fields = fields.Append(field.String("string", "value"))
+
+	require.Len(t, fields, 2)
+}