+# Parallel make doesn't return a fail status when a single subprocess fails,
+# so we need to log the failures and check the log for nonemptiness in order
+# to hand a real status back. This is important for CI/CD.
+FAILLOG=/tmp/advent-test.log
+
+TEST_TARGETS=$(TESTLOADS:%=run-regress-%)
+$(TEST_TARGETS): run-regress-%: %.log