Tests fail on Ember 3

Tests fail in Ember 3:

```
> not ok 9 Chrome 73.0 - [1 ms] - Unit | objectify: it turns an Array into an Ember Array
---
actual: >
false
expected: >
true
stack: >
at Object. (http://localhost:7357/assets/tests.js:67:14)
at runTest (http://localhost:7357/assets/test-support.js:4389:30)
at Test.run (http://localhost:7357/assets/test-support.js:4375:6)
at http://localhost:7357/assets/test-support.js:4596:12
at advanceTaskQueue (http://localhost:7357/assets/test-support.js:3988:6)
at advance (http://localhost:7357/assets/test-support.js:3969:4)
message: >
failed, expected argument to be truthy, was: false
negative: >
false
Log: |
...
not ok 10 Chrome 73.0 - [1 ms] - Unit | objectify: it returns a new Ember Array when given an Ember Array
---
actual: >
false
expected: >
true
stack: >
at Object. (http://localhost:7357/assets/tests.js:74:14)
at runTest (http://localhost:7357/assets/test-support.js:4389:30)
at Test.run (http://localhost:7357/assets/test-support.js:4375:6)
at http://localhost:7357/assets/test-support.js:4596:12
at advanceTaskQueue (http://localhost:7357/assets/test-support.js:3988:6)
at advance (http://localhost:7357/assets/test-support.js:3969:4)
message: >
failed, expected argument to be truthy, was: false
negative: >
false
Log: |
...
ok 11 Chrome 73.0 - [0 ms] - Unit | objectify: it recursively objectifies POJOs
not ok 12 Chrome 73.0 - [3 ms] - Unit | objectify: it recursively objectifies Arrays
---
actual: >
false
expected: >
true
stack: >
at Object. (http://localhost:7357/assets/tests.js:94:14)
at runTest (http://localhost:7357/assets/test-support.js:4389:30)
at Test.run (http://localhost:7357/assets/test-support.js:4375:6)
at http://localhost:7357/assets/test-support.js:4596:12
at advanceTaskQueue (http://localhost:7357/assets/test-support.js:3988:6)
at advance (http://localhost:7357/assets/test-support.js:3969:4)
message: >
Outer array is an Ember Array
negative: >
false
Log: |
```

Has behavior changed?