Test case to check that exists correctly raises for a non-existant file
Test case to check that doesnt_exist correctly raises for a file that does exist
Ensure contains raises when doesnt contain...
Fix typod assertion
Split apart components of contains test cases
Ensure file unexpectedly containing regex triggers test failure
Split filesystem assert mixin test cases for better coherence
Ensure contract of play() returns list of lines
Ensure inventory file default is appropriate
Merge branch 'improve-fsmixin-tests'