Like .use functions as a prepend is there any way to add a .postpend?

[rcuching]

Relatively new to MSW so I may just get this flat out wrong in terms of trying to use the tool. So I figured id ask to try and get some context on why im wrong if I am or if the improvement could be useful.

I have a msw that is set up before a test runs that returns a and url / for example. In my test I have a mutation that changes the return value so now I want a' to be returned from that point on and I do a refetch at /. I have this test that runs the mutation in a nested describe suite. So im using server.use() to try and add additional logic that isnt needed in the other tests. Should i just set an individual server.use in every nested describe instead?

Since I think if .use is functioning as a prepend and MSW goes through the handlers right to left. if i put the a' handler in the use. that will be the handler called first and not the initial handler thats used to set up the server which i expect to run first.

[kettanaito]

Hi, @rcuching. That's a good question.

.use() always prepends request handlers because the order of handlers matters. There is no way to "push" handlers (add to the end) and I don't believe there's ever a reason to do so.

Should i just set an individual server.use in every nested describe instead?

You have a few options here.

Option 1: server.use() in individual describe() blocks

describe('1', () => {
  describe('1.1', () => {
    beforeAll(() => server.use(...overrides))
    afterAll(() => server.resetHandlers())
  })

  describe('1.2', () => {
    beforeAll(() => server.use(...overrides))
    afterAll(() => server.resetHandlers())
  })
})

Don't forget to reset the overrides you add with server.resetHandlers().

Option 2: server.boundary()

If your test suite is rather nested and you don't want to accidentally forget to call .use() or .resetHandlers(), consider using server.boundary().

describe('1', () => {
  describe('1.1', () => {
    it('1.1.1', server.boundary(() => {
      server.use(...overrides)
    }))
  })

  describe('1.2', () => {
    it('1.2.1', server.boundary(() => {
      server.use(...overrides)
    }))
  })
})

server.boundary() wrapper will prevent any handler overrides to escape that test's scope. You don't have to reset any handlers either because nothing leaves the scope of the boundary. I have the feeling you will benefit more from server.boundary() in your case but I will leave that decision up to you.

Related materials

• Network behavior overrides

[rcuching]

Thank you! ill try to put these into use