Lesson 9: unit test - how do you know the expect winner is accounts[2] if it is truly random

[TonyLiVan]

it("picks a winner, resets, and sends money", async () => {
const additionalEntrances = 3 // to test
const startingIndex = 2
for (let i = startingIndex; i < startingIndex + additionalEntrances; i++) { // i = 2; i < 5; i=i+1
raffle = raffleContract.connect(accounts[i]) // Returns a new instance of the Raffle contract connected to player
await raffle.enterRaffle({ value: raffleEntranceFee })
}
const startingTimeStamp = await raffle.getLastTimeStamp() // stores starting timestamp (before we fire our event)

              // This will be more important for our staging tests...
              await new Promise(async (resolve, reject) => {
                  raffle.once("WinnerPicked", async () => { // event listener for WinnerPicked
                      console.log("WinnerPicked event fired!")
                      // assert throws an error if it fails, so we need to wrap
                      // it in a try/catch so that the promise returns event
                      // if it fails.
                      try {
                          // Now lets get the ending values...
                          const recentWinner = await raffle.getRecentWinner()
                          const raffleState = await raffle.getRaffleState()
                          const winnerBalance = await accounts[2].getBalance()
                          const endingTimeStamp = await raffle.getLastTimeStamp()
                          await expect(raffle.getPlayer(0)).to.be.reverted
                          // Comparisons to check if our ending values are correct:

assert.equal(recentWinner.toString(), accounts[2].address).
how do you know the expect winner is accounts[2] if it is truly random ?

                          assert.equal(raffleState, 0)
                          assert.equal(
                              winnerBalance.toString(), 
                              startingBalance // startingBalance + ( (raffleEntranceFee * additionalEntrances) + raffleEntranceFee )
                                  .add(
                                      raffleEntranceFee
                                          .mul(additionalEntrances)
                                          .add(raffleEntranceFee)
                                  )
                                  .toString()
                          )
                          assert(endingTimeStamp > startingTimeStamp)
                          resolve() // if try passes, resolves the promise 
                      } catch (e) { 
                          reject(e) // if try fails, rejects the promise
                      }
                  })

[alymurtazamemon]

@jameslivancouver In the local development, it will always return the same winner index.

[TonyLiVan]

Rewatch the video, noticed that he used console.log() print all accounts ... find the winner first and then assert