tests: add snap version invariant during restore phase of testing

spread.yaml

@@ -2074,12 +2074,14 @@ suites:
         prepare-each: |
             "$TESTSLIB"/prepare-restore.sh --prepare-suite-each
             SNAP_MOUNT_DIR="$(os.paths snap-mount-dir)"
-            case "$SNAP_MOUNT_DIR" in
-                /var/lib/snapd/snap)
-                    ln -sf "$SNAP_MOUNT_DIR" /snap
-                    tests.cleanup defer rm -f /snap
-                    ;;
-            esac
+            if ! os.query is-amazon-linux; then
+                case "$SNAP_MOUNT_DIR" in
+                    /var/lib/snapd/snap)
+                        ln -sf "$SNAP_MOUNT_DIR" /snap
+                        tests.cleanup defer rm -f /snap
+                        ;;
+                esac
+            fi
 
             systemctl restart snapd.service
 

tests/lib/prepare-restore.sh

@@ -702,6 +702,8 @@ prepare_suite() {
 
     # make sure that reset did not break anything
     tests.invariant check snap-mount-dir
+
+    tests.invariant set snapd-version "$(snap version | grep snapd | awk '{print $2}')"
 }
 
 prepare_suite_each() {

tests/lib/tools/tests.invariant

@@ -11,6 +11,7 @@ show_help() {
 	echo "    leftover-defer-sh: defer.sh must not be left over by tests"
 	echo "    broken-snaps: snaps must not be left around that are in a broken state"
 	echo "    segmentation-violations: snapd must not have segmentation-violation errors in journal logs"
+	echo "    snapd-version: the version of snapd during restore must be the same as during project prepare"
     echo "    snap-mount-dir: assert that reported snap mount directory is the same as at test start"
     echo
     echo "Supported invariants for 'set' action:"
@@ -261,6 +262,26 @@ check_snap_mount_dir() {
 	fi
 }
 
+set_snapd_version() {
+    echo "$1" > "$TESTSTMP/tests.invariant.snapd-version"
+}
+
+check_snapd_version() {
+	if tests.nested is-nested; then
+		return 0
+	fi
+	if command -v snap && systemctl is-active snapd.socket && systemctl is-active snapd.service; then
+		if tests.info is-snapd-from-archive && not tests.info is-reexec-enabled; then
+			# re-exec may be explicitly disabled in the test variant, in which case the version will not match
+			return 0
+		fi
+		snap version | grep snapd | grep -qF "$(cat "${TESTSTMP}"/tests.invariant.snapd-version)" || {
+			echo "tests.invariant: snapd version mismatch, expected $(cat "${TESTSTMP}"/tests.invariant.snapd-version) but got $(snap version | grep snapd | awk '{print $2}')" >&2
+			return 1
+		}
+	fi
+}
+
 check_invariant() {
 	case "$1" in
 		root-files-in-home)
@@ -296,6 +317,9 @@ check_invariant() {
         snap-mount-dir)
             check_snap_mount_dir "$1"
             ;;
+		snapd-version)
+			check_snapd_version
+			;;
 		*)
 			echo "tests.invariant: unknown invariant $1" >&2
 			exit 1
@@ -316,6 +340,7 @@ main() {
 	segmentation-violations
 	check-fakestore-cleaned
     snap-mount-dir
+	snapd-version
 	"
 
 	case "$action" in
@@ -345,6 +370,10 @@ main() {
                     shift
                     set_snap_mount_dir "$*"
                     ;;
+			     snapd-version)
+				 	shift
+					set_snapd_version "$*"
+				 	;;
                  *)
                      echo "tests.invariant: unsupported set action"
                      exit 1