Skip the bus's docker tests loudly where there is no docker, and run them by name in a docker step of the merge check where there is (ADR 0480 clause 6)

merge-check.sh

@@ -192,6 +192,19 @@ for m in $touched; do
 	# another process) run here and nowhere else: the unit suite stays under a second (novox/hq playbook 07).
 	(cd "modules/$m" && CGO_ENABLED=$cgo GOPRIVATE=git.novox.be go vet -tags integration ${modfile:+"-modfile=$modfile"} ./... &&
 		CGO_ENABLED=$cgo GOPRIVATE=git.novox.be go test -tags integration ${modfile:+"-modfile=$modfile"} $race -count=1 ./...)
+	# The docker tests of the bus's snapshot program and entrypoint (novox/hq ADR 0480 clause 6) start throwaway nats
+	# containers, and the Go toolchain container holds no docker, so above they skip with a "NOT RUN" line. Where the
+	# build seat says docker exists (MESH_CHECK_DOCKER=1) they run here by name, and a missing docker fails the check
+	# (MESH_REQUIRE_DOCKER=1 makes the tests fail instead of skip). Without it the step says it did not run.
+	if [ "$m" = nats ]; then
+		if [ "${MESH_CHECK_DOCKER:-}" = 1 ]; then
+			(cd modules/nats && MESH_REQUIRE_DOCKER=1 CGO_ENABLED=$cgo GOPRIVATE=git.novox.be go test -tags integration ${modfile:+"-modfile=$modfile"} -count=1 \
+				-run 'TestTheDeclaredDumpRunsInTheBussImage|TestTheEntrypointReloadsTheServerWithoutDroppingAConnection|TestTheStoreSurvivesTheNewDeclarationTheOldAndTheNewAgain|TestASnapshotOfALiveBusRestoresToTheSameContent|TestTheSnapshotUserCannotChangeTheBus' \
+				./cmd/mesh-nats-snapshot) || { echo "the bus's docker tests failed"; exit 1; }
+		else
+			echo "NOT RUN: the bus's five docker tests (modules/nats/cmd/mesh-nats-snapshot) skipped: this check has no docker (MESH_CHECK_DOCKER is not 1)"
+		fi
+	fi
 done
 if [ -n "$untestable" ]; then
 	echo "the check fails: the tests of$untestable could not run (novox/hq issue 385)"

modules/nats/cmd/mesh-nats-snapshot/live_test.go

@@ -60,7 +60,13 @@ var snapshotGrants = struct{ publish, subscribe []string }{
 func needDocker(t *testing.T) {
 	t.Helper()
 	if _, err := exec.LookPath("docker"); err != nil {
-		t.Fatalf("these tests start throwaway nats containers and need docker on the machine that runs them: %v", err)
+		// The Go toolchain container of the merge check holds no docker. Where docker is expected
+		// (MESH_REQUIRE_DOCKER=1, which merge-check.sh sets for its docker step) its absence is a failure.
+		if os.Getenv("MESH_REQUIRE_DOCKER") == "1" {
+			t.Fatalf("MESH_REQUIRE_DOCKER=1 and there is no docker here: %v", err)
+		}
+		t.Skipf("NOT RUN: this test starts a throwaway nats container and there is no docker in this toolchain (%v); "+
+			"it is proof only where merge-check.sh's docker step runs it (MESH_CHECK_DOCKER=1)", err)
 	}
 }