vue-test-utils-classes

Repo to reproduce typescript error

Steps to reproduce

npm install

npm run serve

what happens

typescript yield an error:

ERROR in /Users/yawenxiao/Personal/vue-test-utils-classes/tests/unit/HelloWorld.spec.ts
10:30 Property 'includes' does not exist on type 'void | string[]'.
  Property 'includes' does not exist on type 'void'.
     8 |       propsData: { msg },
     9 |     });
  > 10 |     expect(wrapper.classes().includes('a')).toBe(false);
       |                              ^
    11 |   });
    12 | });
    13 |
Version: typescript 2.9.1

how to solve

I read the source code and find the type definition of the classes() method is this:

classes(): Array<string> | void

Maybe because the return value could be void so it does not have a includes method.

When I change it to :

classes(): Array<string>

the error disappears and everything works ok.