You could test the output using GNU-Make. In your Makefile:
.ONESHELL:
SHELL = bash
test:
diff <(./test/program1 <args>) ./tests/expected_output1.json
diff <(./test/program2 <args>) ./tests/expected_output2.json
Then make test should pass or fail depending on whether the programs gave exactly the output they were expected too or not.