Jenkins CI build passing when it shouldn't

I am following this tutorial, and I am encountering some difficulties. I should make clear that I'm using it as a guide, rather than following it exactly. I have set it up thus far using bitbucket rather than Github, and it is hosted locally rather than remotely. Other than that I have installed some security plugins and that's about all.

I'm up to the section where it tells me to set the shell job

npm install
./script/test

at first, the build failed as expected, but when examining the output I realized that was because I hadn't set the shell path to use git-bash.exe, once that was fixed the build passed( I had changed it back to "hello world" to be sure it would pass) and all seemed normal. But once I changed it so the build should fail, I realized it was passing regardless. I checked the workspace and it has all the right files. I downloaded the zip and ran the ./script/test shell file and it fails, so why does the build pass?

Your assistance would be appreciated.