fstests: add test for 0 sized streaming upload

fstest/fstests/fstests.go

@@ -18,6 +18,7 @@ import (
 	"path/filepath"
 	"reflect"
 	"sort"
+	"strconv"
 	"strings"
 	"testing"
 	"time"
@@ -1571,6 +1572,8 @@ func Run(t *testing.T, opt *Opt) {
 					t.Skip("FS has no PutStream interface")
 				}
 
+				for _, contentSize := range []int{0, 100} {
+					t.Run(strconv.Itoa(contentSize), func(t *testing.T) {
 						file := fstest.Item{
 							ModTime: fstest.Time("2001-02-03T04:05:06.499999999Z"),
 							Path:    "piped data.txt",
@@ -1581,7 +1584,6 @@ func Run(t *testing.T, opt *Opt) {
 							err        error
 							obj        fs.Object
 							uploadHash *hash.MultiHasher
-					contentSize = 100
 						)
 						retry(t, "PutStream", func() error {
 							contents := random.String(contentSize)
@@ -1602,6 +1604,8 @@ func Run(t *testing.T, opt *Opt) {
 						file.Check(t, obj, remote.Precision())
 						require.NoError(t, obj.Remove(ctx))
 					})
+				}
+			})
 
 			// TestInternal calls InternalTest() on the Fs
 			t.Run("Internal", func(t *testing.T) {