Ember Testing: Why use Assert.?

I see a lot of examples (including ember-cli generated tests) that use assert.function() but I can use the function as is, so am I doing something wrong, or do examples just show not-really-necessary qualifiers?

For example, either of these work in a new generated unit test:

assert.expect(1);

expect(1);

Why ever do the first one if the second one works?