toBeArrayOfSize() throwing error on constructing message

When using:

expect(arrayOfObjects).toBeArrayOfSize(n)

I am getting errors from expect-more on creation of the jest error message when the test fails:

  TypeError: Cannot convert object to primitive value
      at Array.join (<anonymous>)
      at Array.toString (<anonymous>)
      at message (node_modules/expect-more-jest/dist/to-be-array-of-size.js:7:51)
      at message (node_modules/expect-more-jest/dist/lib/create-result.js:6:62)
      at getMessage (node_modules/expect/build/index.js:209:15)
      at processResult (node_modules/expect/build/index.js:327:25)
      at Object.toBeArrayOfSize (node_modules/expect/build/index.js:396:16)

[JamieMason]

Released in 4.0.2, please let me know of any issues and thanks for all your work on investigating this issue.

[robross0606]

Here is a more formal test you could use:

describe('Prototypeless Bug', () => {
  const withPrototypes = []
  const withoutPrototypes = []

  beforeAll(() => {
    const createTestObject = (index, withProto) => {
      const obj = withProto ? {} : Object.create(null)
      obj.name = `Object ${index}`
      obj.id = index
      return obj
    }
    for (let i = 0; i < 5; i++) {
      withPrototypes[i] = createTestObject(i + 1, true)
      withoutPrototypes[i] = createTestObject(i + 1, false)
    }
  })

  it('Exception on failing test with array of objects', typeName => {
    let expectedError
    try {
      expect(withPrototypes).toBeArrayOfSize(1)
    } catch (error) {
      expect(error).toMatchInlineSnapshot(
        `[Error: expected [object Object],[object Object],[object Object],[object Object],[object Object] to be an array containing exactly 1 items]`
      )
      expectedError = error
    }
    expect(expect(withoutPrototypes).toBeArrayOfSize(1)).toThrow(error.message)
  })
})

This proves that object literals create objects with prototypes since the first set of expectations work. The second usage should match behavior of the first but fails due to objects not having prototypes.