Add some tests for the external gc daemon

tests/gc-external-daemon.sh

@@ -0,0 +1,37 @@
+source common.sh
+
+export NIX_GC_SOCKET_PATH=$TEST_ROOT/gc.socket
+startGcDaemon() {
+    # Start the daemon, wait for the socket to appear.  !!!
+    # ‘nix-daemon’ should have an option to fork into the background.
+    rm -f $NIX_GC_SOCKET_PATH
+    $(dirname $(which nix))/../libexec/nix/nix-find-roots \
+        -l "$NIX_GC_SOCKET_PATH" \
+        -d "$NIX_STATE_DIR" \
+        -s "$NIX_STORE_DIR" \
+            &
+    for ((i = 0; i < 30; i++)); do
+        if [[ -S $NIX_GC_SOCKET_PATH ]]; then break; fi
+        sleep 1
+    done
+    pidGcDaemon=$!
+    trap "killGcDaemon" EXIT
+}
+
+killGcDaemon() {
+    kill $pidGcDaemon
+    for i in {0.10}; do
+        kill -0 $pidGcDaemon || break
+        sleep 1
+    done
+    kill -9 $pidGcDaemon || true
+    wait $pidGcDaemon || true
+    trap "" EXIT
+}
+
+startGcDaemon
+
+bash ./gc.sh
+bash ./gc-concurrent.sh
+bash ./gc-runtime.sh
+bash ./gc-auto.sh

tests/local.mk

@@ -2,6 +2,7 @@ nix_tests = \
   flakes.sh \
   ca/gc.sh \
   gc.sh \
+  gc-external-daemon.sh \
   remote-store.sh \
   lang.sh \
   fetchMercurial.sh \