unit tests fail on docker image php:7.1.1

[simon]

The bigbucket build pipeline was timing out. Using a much smaller test case I get a unit test error to this command which is attached.

vendor/bin/phpunit ThinbusTestQuick.php

[simon]

same issue with `docker run -it php:7.0.26 /bin/bash then the following:

apt-get update && apt-get install -y unzip git
git clone https://[e-mail]/simon_massey/thinbus-php.git
cd thinbus-php
curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
composer install
vendor/bin/phpunit ThinbusTestQuick.php

[simon]

That was a real pain. I had to create a custom image for 7.0.26 with "php7.0 php-xml php-mbstring php7.0-bcmath" for things to work. So this is something to do with not running with a proper native math package such as bcmath.