tests/check.sh: Fix a race

Fixes this random failure:

    error: hash mismatch in fixed-output derivation '/tmp/nix-shell.EUgAVU/nix-test/tests/check/store/sfps3l3c5n7dabpx34kigxnfhmrwk2h6-dummy.drv':
             specified: sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=
                got:    sha256-0qhPS4tlCTfsj3PNi+LHSt1akRumTfJ0WO2CKdqASiY=

which happens because multiple tests were writing to ./dummy.

3 files changed, 5 insertions, 4 deletions

diff --git a/tests/add.sh b/tests/add.sh
index e26e05843..5c3eed793 100644
--- a/tests/add.sh
+++ b/tests/add.sh
@@ -9,7 +9,7 @@ echo $path2
 if test "$path1" != "$path2"; then
     echo "nix-store --add and --add-fixed mismatch"
     exit 1
-fi    
+fi
 
 path3=$(nix-store --add-fixed sha256 ./dummy)
 echo $path3
diff --git a/tests/check.nix b/tests/check.nix
index bca04fdaf..ec455ae2d 100644
--- a/tests/check.nix
+++ b/tests/check.nix
@@ -44,7 +44,7 @@ with import ./config.nix;
   };
 
   hashmismatch = import <nix/fetchurl.nix> {
-    url = "file://" + toString ./dummy;
+    url = "file://" + builtins.getEnv "TMPDIR" + "/dummy";
     sha256 = "0mdqa9w1p6cmli6976v4wi0sw9r4p5prkj7lzfd1877wk11c9c73";
   };
 
diff --git a/tests/check.sh b/tests/check.sh
index 5f4997e28..d26d4d8fc 100644
--- a/tests/check.sh
+++ b/tests/check.sh
@@ -74,12 +74,13 @@ nix-build check.nix -A fetchurl --no-out-link --check
 nix-build check.nix -A fetchurl --no-out-link --repair
 [[ $(cat $path) != foo ]]
 
+echo 'Hello World' > $TMPDIR/dummy
 nix-build check.nix -A hashmismatch --no-out-link || status=$?
 [ "$status" = "102" ]
 
-echo -n > ./dummy
+echo -n > $TMPDIR/dummy
 nix-build check.nix -A hashmismatch --no-out-link
-echo 'Hello World' > ./dummy
+echo 'Hello World' > $TMPDIR/dummy
 
 nix-build check.nix -A hashmismatch --no-out-link --check || status=$?
 [ "$status" = "102" ]