test: implement safe abstraction using the Wake trait

[nurmohammed840]

No description provided.

[Darksonn]

This seems to contain two independent changes: using the Wake trait and a new block_on method. Could you explain what you're trying to do?

[nurmohammed840]

Wake trait provides a safe abstraction for creating Waker from an Arc pointer data:

tokio/tokio-test/src/task.rs

Lines 59 to 61 in 9cc4a81

	struct MockTask {
	waker: Arc<ThreadWaker>,
	}

This reduces both boilerplate and, more importantly unsafe code.

---

I'm really surprised that there isn't a block_on function:
Although original implementation do support this:

tokio/tokio-test/src/task.rs

Lines 209 to 212 in 9cc4a81

	ThreadWaker {
	state: Mutex::new(IDLE),
	condvar: Condvar::new(),
	}

tokio/tokio-test/src/task.rs

Lines 245 to 247 in 9cc4a81

	// The other half is sleeping, so we wake it up.
	assert_eq!(prev, SLEEP);
	self.condvar.notify_one();

Original implementation has Condvar, But it isn't used anywhere.
Also the name ThreadWaker implies that it's used to wake a sleeping thread, but no thread is actually sleeping (because there is no block_on), I believe the author may have forgotten to include block_on function.

This is my main reason to add block_on

It could also be useful as a basic future executor, similar to futures::executor::block_on

[Darksonn]

We use tokio_test::task::spawn quite a lot in our test suite, and we don't need it to include a block_on there. Usually, it's used to manually call poll in a convenient manner. What are you trying to use it for?

[nurmohammed840]

This could be useful outside of Tokio test suites for general-purpose future execution.
Most test cases don't require an I/O event loop or Timer

It's also well-suited for benchmarking asynchronous code due to its lightweight nature.

In some cases, you may want to avoid a runtime. For example, when running tools like Miri,
Currently #[tokio::test] cannot be used to test async code using miri.

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Most importantly original implementation has already support for it.

Maybe we should consider replacing entire wake() function with just single AtomicBool::store operation, if we decide to drop block_on support.

tokio/tokio-test/src/task.rs

Line 230 in 161b8c8

fn wake(&self) {