Fix node folding in case of empty rules (pool with size 1), add a test

tests/common.sh

@@ -87,6 +87,22 @@ wait_etcd()
     done
 }
 
+wait_condition()
+{
+    sec=$1
+    check=$2
+    proc=$3
+    i=0
+    while [[ $i -lt $sec ]]; do
+        eval "$check" && break
+        if [ $i -eq $sec ]; then
+            format_error "$proc couldn't finish in $sec seconds"
+        fi
+        sleep 1
+        i=$((i+1))
+    done
+}
+
 if [[ -n "$ANTIETCD" ]]; then
     ETCDCTL="node mon/node_modules/.bin/anticli -e $ETCD_URL"
     MON_PARAMS="--use_antietcd 1 --antietcd_data_dir ./testdata --antietcd_persist_interval 500 $MON_PARAMS"

tests/run_3osds.sh

@@ -127,22 +127,6 @@ try_reweight()
     sleep 3
 }
 
-wait_condition()
-{
-    sec=$1
-    check=$2
-    proc=$3
-    i=0
-    while [[ $i -lt $sec ]]; do
-        eval "$check" && break
-        if [ $i -eq $sec ]; then
-            format_error "$proc couldn't finish in $sec seconds"
-        fi
-        sleep 1
-        i=$((i+1))
-    done
-}
-
 wait_finish_rebalance()
 {
     sec=$1

tests/test_failure_domain.sh

@@ -31,4 +31,8 @@ sleep 2
 $ETCDCTL get --prefix /vitastor/pg/config --print-value-only | \
     jq -s -e '([ .[0].items["1"] | .[].osd_set | map_values(. | tonumber) | select((.[0] <= 4) != (.[1] <= 4)) ] | length) == 4'
 
+# test pool with size 1
+build/src/cmd/vitastor-cli --etcd_address $ETCD_URL create-pool size1pool -s 1 -n 1 --force
+wait_condition 10 "$ETCDCTL get --prefix /vitastor/pg/config --print-value-only | jq -s -e '.[0].items["'"'"2"'"'"]'"
+
 format_green OK