`npm test` fails with "TypeError: Cannot read property 'write' of null"

[aidanharris]

> node --version
v6.10.2

> [email protected] test /home/aidan/node-libquassel
> tape test/test.js

TAP version 13
# setup
not ok 1 test timed out after 3000ms
  ---
    operator: fail
  ...
not ok 2 plan != count
  ---
    operator: fail
    expected: 3
    actual:   1
  ...
# login
/home/aidan/node-libquassel/lib/libquassel.js:1722
        self.qtsocket.write(obj);
                     ^

TypeError: Cannot read property 'write' of null
    at /home/aidan/node-libquassel/lib/libquassel.js:1722:22
    at Quassel.loginError (/home/aidan/node-libquassel/test/test.js:9:5)
    at Quassel.login (/home/aidan/node-libquassel/lib/libquassel.js:1716:10)
    at Test.<anonymous> (/home/aidan/node-libquassel/test/test.js:37:13)
    at Test.bound [as _cb] (/home/aidan/node-libquassel/node_modules/tape/lib/test.js:66:32)
    at Test.run (/home/aidan/node-libquassel/node_modules/tape/lib/test.js:85:10)
    at Test.bound [as run] (/home/aidan/node-libquassel/node_modules/tape/lib/test.js:66:32)
    at Immediate.next (/home/aidan/node-libquassel/node_modules/tape/lib/results.js:71:15)
    at runCallback (timers.js:666:20)
    at tryOnImmediate (timers.js:639:5)
npm ERR! Test failed.  See above for more details.