Makefile rule with multiline shell script recipe

Makefile

all: foo.sh

check: foo.sh
	@set -eu; \
	echo "Running $<"; \
	output=$$(sh $<); \
	expect=42; \
	if [ "$$output" != "$$expect" ]; then \
		echo "*** CHECK FAILED: expected $$expect, got $$output"; \
	fi

foo.sh:
	echo "echo 42" > $@

clean:
	rm -f foo.sh

.PHONY: all check clean

The recipe for check can be simplified by adding .ONESHELL:

.ONESHELL:
check: foo.sh
	@set -eu
	echo "Running $<"
	output=$$(sh $<)
	expect=42
	if [ "$$output" != "$$expect" ]; then
		echo "*** CHECK FAILED: expected $$expect, got $$output"
	fi

@aprell Great tip regarding .ONESHELL!!

This was just what I needed. Many thanks for this tip.
In MacOS, for if statements with multiple lines work properly, I needed to update make from 3.81 to 4.2.1:

brew install make