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assert_called_once

assert_called_once checks that a subscriber's handler ran exactly once: one delivery, or one batch.

It counts handler calls in the record, subscriber(name), not messages: a batch handler called with five orders counts once. A delivery that did not decode counts too: the record holds it although the body never ran. It returns the assertions, so with, with_raw and settled chain after it and read that one call. On failure it panics with the number of calls it found. assert_called(n) checks any other number, and assert_not_called checks that there was no call.

Example​

examples/testing_subscriber_calls.rs
#[tokio::test]
async fn the_handler_ran_once() -> Result<(), Box<dyn Error>> {
    let tb = TestApp::start(app()).await?;
    tb.broker::<MemoryBroker>()
        .message(&Order { id: 7 })
        .to("orders")
        .publish()
        .await?;

    tb.broker::<MemoryBroker>()
        .subscriber("orders")
        .assert_called_once();
    Ok(())
}