Unable to understand the test for checkUpkeep function

[decentralized-86]

 describe("checkUpkeep", function () {
              it("returns false if people haven't sent any ETH", async () => {
                  await network.provider.send("evm_increaseTime", [interval.toNumber() + 1])
                  await network.provider.request({ method: "evm_mine", params: [] })
                  const { upkeepNeeded } = await raffle.callStatic.checkUpkeep("0x") // upkeepNeeded = (timePassed && isOpen && hasBalance && hasPlayers)
                  assert(!upkeepNeeded)
              })

Foe what here is callStatic used ...?? what if it was

const { upkeepNeeded } = await raffle.checkUpkeep("0x")```

[alymurtazamemon]

@decentralized-86 Sometimes we do not want to do a transaction when calling a function, we just wanna read the data, we can mark the function as view/pure but another thing that is very helpful in tests is a callStatic. Appending callStatic while calling a function in tests will not create a transaction but it simulates the transaction and give the results.

[decentralized-86]

U mean that To Read From blockchain we use view/pure but if the function is not view/pure that it would cost ETH so callStatic is used Right

[alymurtazamemon]

@decentralized-86 nope! suppose a sum function that takes two numbers and returns a sum of these. Now you want a sum of two numbers but you do not want to count it as a transaction or leave a transaction for miners to count it. That is what callStatic does it perform that function but does not count it as a transaction.

By the way, if you do not know, everything you do on blockchain counts as a transaction, for example just getting a count value of a counter variable is a transaction.

[AlexCZM]

https://docs.ethers.io/v5/api/contract/contract/#contract-callStatic

Any function can be called with 'callStatic'. Not only view/ pure ones as I initially thought.
Where it can be used:
This in some cases can be used to determine if a transaction will fail or succeed.