Is there a good esp8266 simulator software that can be used to automate testing? Is it possible to get code written on Arduino IDE to run on these simulators?
As of Jan 2023...
The docs for the RIOT OS (an IoT OS) explain how to compile and use an ESP8266 version of QEMU for Xtensa. The docs contain the compile instructions:
cd /my/source/dir
git clone https://github.com/gschorcht/qemu-xtensa
cd qemu-xtensa/
git checkout xtensa-esp8266
export QEMU=/path/to/esp/qemu
./configure --prefix=$QEMU --target-list=xtensa-softmmu --disable-werror
make
make install
Actually, the gschorcht/qemu-xtensa repo (last updated 2018) is a fork of the original OSLL/qemu-xtensa project, so you could use the original repo:
cd /my/source/dir
git clone https://github.com/OSLL/qemu-xtensa
cd qemu-xtensa/
git checkout xtensa-esp8266
export QEMU=/path/to/esp/qemu
./configure --prefix=$QEMU --target-list=xtensa-softmmu --disable-werror
make
make install
Unfortunately, that branch hasn't been updated since 2019 so it may not compile on very recent OS versions. For instance, I got an error: expected unqualified-id error while trying to compile on macOS 12.14. So, someone probably needs to fix those compile errors.