How to have GNU make explicitly test for failure?

Put a - before the command, e.g.:

-myProg bad_input >> test.log

GNU make will then ignore the process exit code.

Try running it as

make -i

or

make --ignore-errors

which ignores all errors in all rules.

I'd also suggest running it as

make -i 2>&1 | tee results

so that you got all the errors and output to see what happened.

Just blindly continuing on after an error is probably not what you're really wanting to do. The make utility, by its very nature, is usually relying on successful completion of previous commands so that it can use the artefacts of those commands as pre-requisites for commands to be executed later on.

BTW I'd highly recommend getting a copy of the O'Reilly book on make. The first edition has an excellent overview of the basic nature of make, specifically its backward chaining behaviour. Later editions are still good but the first ed. still has the clearest explanation of what's actually happening. In fact, my own copy is the first thing I pass to people who come to me to ask "WTF? questions" about make! (-: