diff --git a/nix/tests.nix b/nix/tests.nix
index 93a2395b8..1db5fe102 100644
--- a/nix/tests.nix
+++ b/nix/tests.nix
@@ -184,8 +184,10 @@ let
         # temporary directory to collect data in
         tmpdir="$(mktemp -d)"
 
-        # we keep the tmpdir when an error occurs for debugging and only remove it on success
-        trap 'echo Temporary directory kept at: $tmpdir' ERR SIGINT SIGTERM
+        # we keep the tmpdir when an error occurs for debugging
+        trap 'echo Temporary directory kept at: $tmpdir' ERR
+        # remove the tmpdir when cancelled (postgrest-watch)
+        trap 'rm -rf "$tmpdir"' SIGINT SIGTERM
 
         # build once before running all the tests
         ${cabal-install}/bin/cabal v2-build ${devCabalOptions} --enable-tests all
@@ -199,7 +201,7 @@ let
         ${withTmpDb postgresql} ${cabal-install}/bin/cabal v2-test ${devCabalOptions}
 
         # collect all the tix files
-        ${ghc}/bin/hpc sum  --union --exclude=Paths_postgrest --output="$tmpdir"/tests.tix "$tmpdir"/io.tix "$tmpdir"/spec.tix
+        ${ghc}/bin/hpc sum  --union --exclude=Paths_postgrest --output="$tmpdir"/tests.tix "$tmpdir"/io*.tix "$tmpdir"/spec.tix
 
         # prepare the overlay
         ${ghc}/bin/hpc overlay --output="$tmpdir"/overlay.tix test/coverage.overlay
diff --git a/test/io-tests/test_io.py b/test/io-tests/test_io.py
index 6c7517f4a..7b5d75e64 100644
--- a/test/io-tests/test_io.py
+++ b/test/io-tests/test_io.py
@@ -73,12 +73,22 @@ def defaultenv():
     }
 
 
+def hpctixfile():
+    "Returns an individual filename for each test, if the HPCTIXFILE environment variable is set."
+    if "HPCTIXFILE" not in os.environ:
+        return ""
+
+    tixfile = pathlib.Path(os.environ["HPCTIXFILE"])
+    test = hash(os.environ["PYTEST_CURRENT_TEST"])
+    return tixfile.with_suffix(f".{test}.tix")
+
+
 def dumpconfig(configpath=None, env=None, stdin=None):
     "Dump the config as parsed by PostgREST."
     env = env or {}
 
     command = [POSTGREST_BIN, "--dump-config"]
-    env["HPCTIXFILE"] = os.getenv("HPCTIXFILE", "")
+    env["HPCTIXFILE"] = hpctixfile()
 
     if configpath:
         command.append(configpath)
@@ -88,7 +98,7 @@ def dumpconfig(configpath=None, env=None, stdin=None):
     )
 
     process.stdin.write(stdin or b"")
-    result = process.communicate()[0]
+    result = process.communicate(timeout=5)[0]
     process.kill()
     process.wait()
     if process.returncode != 0:
@@ -112,7 +122,7 @@ def run(configpath=None, stdin=None, env=None, port=None):
             baseurl = "http+unix://" + urllib.parse.quote_plus(str(socketfile))
 
         command = [POSTGREST_BIN]
-        env["HPCTIXFILE"] = os.getenv("HPCTIXFILE", "")
+        env["HPCTIXFILE"] = hpctixfile()
 
         if configpath:
             command.append(configpath)
@@ -127,8 +137,12 @@ def run(configpath=None, stdin=None, env=None, port=None):
 
             yield PostgrestProcess(process=process, session=PostgrestSession(baseurl))
         finally:
-            process.kill()
-            process.wait()
+            process.terminate()
+            try:
+                process.wait(timeout=1)
+            except:
+                process.kill()
+                process.wait()
 
 
 def freeport():