Use "set -x" in the tests to see where a test fails

tests/common.sh.in

@@ -80,3 +80,5 @@ fail() {
     echo "$1"
     exit 1
 }
+
+set -x

tests/referrers.sh

@@ -10,6 +10,7 @@ touch $reference
 
 echo "making registration..."
 
+set +x
 for ((n = 0; n < $max; n++)); do
     storePath=$NIX_STORE_DIR/$n
     echo -n > $storePath
@@ -19,6 +20,7 @@ for ((n = 0; n < $max; n++)); do
     fi
     echo $storePath; echo; echo 2; echo $reference; echo $ref2
 done > $TEST_ROOT/reg_info
+set -x
 
 echo "registering..."