getting payload from a substrate event back in rust tests - rust

Question

i've created my first substrate project successful and the built pallet also works fine. Now i wanted to create tests for the flow and the provided functions.
My flow is to generate a random hash and store this hash associated to the sender of the transaction
let _sender = ensure_signed(origin)?;
let nonce = Nonce::get();
let _random_seed = <randomness_collective_flip::Module<T>>::random_seed();
let random_hash = (_random_seed, &_sender, nonce).using_encoded(T::Hashing::hash);
ensure!(!<Hashes<T>>::contains_key(random_hash), "This new id already exists");
let _now = <timestamp::Module<T>>::get();
let new_elem = HashElement {
id: random_hash,
parent: parent,
updated: _now,
created: _now
};
<Hashes<T>>::insert(random_hash, new_pid);
<HashOwner<T>>::insert(random_hash, &_sender);
Self::deposit_event(RawEvent::Created(random_hash, _sender));
Ok(())
works good so far, when now i want to test the flow with a written test, i want to check if the hash emitted in the Created event is also assigned in the HashOwner Map. For this i need to get the value out of the event back.
And this is my problem :D i'm not professional in rust and all examples i found are expecting all values emitted in the event like this:
// construct event that should be emitted in the method call directly above
let expected_event = TestEvent::generic_event(RawEvent::EmitInput(1, 32));
// iterate through array of `EventRecord`s
assert!(System::events().iter().any(|a| a.event == expected_event));
When debugging my written test:
assert_ok!(TemplateModule::create_hash(Origin::signed(1), None));
let events = System::events();
let lastEvent = events.last().unwrap();
let newHash = &lastEvent.event;
i see in VSCode that the values are available:
debug window of vs code
but i dont know how to get this Hash in a variable back... maybe this is only a one liner ... but my rust knowledge is damn too small :D
thank you for your help

Answer 1

Here's a somewhat generic example of how to parse and check events, if you only care about the last event that your module put in system and nothing else.
assert_eq!(
System::events()
// this gives you an EventRecord { event: ..., ...}
.into_iter()
// map into the inner `event`.
.map(|r| r.event)
// the inner event is like `OuterEvent::mdouleEvent(EventEnum)`. The name of the outer
// event comes from whatever you have placed in your `delc_event! {}` in test mocks.
.filter_map(|e| {
if let MetaEvent::templateModule(inner) = e {
Some(inner)
} else {
None
}
})
.last()
.unwrap(),
// RawEvent is defined and imported in the template.rs file.
// val1 and val2 are things that you want to assert against.
RawEvent::Created(val1, val2),
);
Indeed you can also omit the first map or do it in more compact ways, but I have done it like this so you can see it step by step.
Print the System::events(), this also helps.

Answer 2

I now got it from the response of kianenigma :)
I wanted to reuse the given data in the event:
let lastEvent = System::events()
// this gives you an EventRecord { event: ..., ...}
.into_iter()
// map into the inner `event`.
.map(|r| r.event)
// the inner event is like `OuterEvent::mdouleEvent(EventEnum)`. The name of the outer
// event comes from whatever you have placed in your `delc_event! {}` in test mocks.
.filter_map(|e| {
if let TestEvent::pid(inner) = e {
Some(inner)
} else {
None
}
})
.last()
.unwrap();
if let RawEvent::Created(newHash, initiatedAccount) = lastEvent {
// there are the values :D
}
this can maybe be written better but this helps me :)