> This was causing a lot of test cases not not be very meaningful because
> multiple configuration options were combined into one line.
>
> The changes in test output with this fix make sense and look like:
>
> ```diff
> - testnet=1 regtest=1 || test
> + testnet=1 regtest=1 || error: Invalid combination of -regtest, -testnet and -chain. Can use at > > most one.
> ```
> Issue was reported and debugged by
> Wladimir J. van der Laan <laanwj@protonmail.com> in
> https://github.com/bitcoin/bitcoin/pull/17385#issuecomment-550033222
This is a backport of Core PR17388