760a2123dd
The `with_ancestry` methods on `NewSpan` and `ExpectedEvent` provide a way to match whether the span or event is a contextual or explicit root or if it has a contextual or explicit parent span. However, in the case of matching on a contextual or explicit parent span, only the span name could be used for matching. This is sufficiently precise when testing tracing instrumentation in other libraries or applications as opposed to testing tracing itself. It is likely that a user would like to test that some span or event has a specific span as a parent, and not just any span with a specific name, in many cases, all the possible parent spans may have the same name. This is the case when testing tracing instrumentation in Tokio. To solve this problem, the `Ancestry` struct was renamed to `ExpectedAncestry` and in the case of expecting an explicit or conextual parent, an `ExpectedSpan` object can be passed in. This provides the maximum possible flexibility. The convenience functions in the `expect` module now take `Into<ExpectedSpan>` so that existing tests that pass a string type object for the parent will see the same behaviour as previously and shorthand use for expected Ids is also available. Additionally, the span checking code has been unified between the `MockCollector` and `MockSubscriber` cases and the assertion descriptions have been improved to make them more readable.
tracing-mock
Utilities for testing [tracing][tracing] and crates that uses it.
Overview
[tracing] is a framework for instrumenting Rust programs to collect
structured, event-based diagnostic information. tracing-mock provides
tools for making assertions about what tracing diagnostics are emitted
by code under test.
Compiler support: requires rustc 1.63+
Usage
tracing-mock crate provides a mock
Collector
that allows asserting on the order and contents of
spans and
events.
As tracing-mock isn't available on crates.io
yet, you must import it via git. When using tracing-mock with the
tracing 0.1 ecosystem, it is important that you also override the
source of any tracing crates that are transient dependencies. For
example, the Cargo.toml for your test crate could contain:
[dependencies]
lib-under-test = "1.0" # depends on `tracing`
[dev-dependencies]
tracing-mock = { git = "https://github.com/tokio-rs/tracing", branch = "v0.1.x", version = "0.1" }
tracing = { git = "https://github.com/tokio-rs/tracing", branch = "v0.1.x", version = "0.1" }
[patch.crates-io]
tracing = { git = "https://github.com/tokio-rs/tracing", branch = "v0.1.x" }
tracing-core = { git = "https://github.com/tokio-rs/tracing", branch = "v0.1.x" }
Examples
The following examples are for the master branch. For examples that
will work with tracing from [crates.io], please check the
v0.1.x
branch.
Below is an example that checks that an event contains a message:
use tracing::subscriber::with_default;
use tracing_mock::{subscriber, expect, field};
fn yak_shaving() {
tracing::info!("preparing to shave yaks");
}
let (subscriber, handle) = subscriber::mock()
.event(expect::event().with_fields(expect::message("preparing to shave yaks")))
.only()
.run_with_handle();
with_default(subscriber, || {
yak_shaving();
});
handle.assert_finished();
Below is a slightly more complex example. tracing-mock asserts that, in order:
- a span is created with a single field/value pair
- the span is entered
- an event is created with the field
number_of_yaks, a corresponding value of 3, and the message "preparing to shave yaks", and nothing else - an event is created with the field
all_yaks_shaved, a corresponding value oftrue, and the message "yak shaving completed" - the span is exited
- no further traces are received
use tracing::subscriber::with_default;
use tracing_mock::{subscriber, expect};
#[tracing::instrument]
fn yak_shaving(number_of_yaks: u32) {
tracing::info!(number_of_yaks, "preparing to shave yaks");
let number_shaved = number_of_yaks; // shave_all
tracing::info!(
all_yaks_shaved = number_shaved == number_of_yaks,
"yak shaving completed."
);
}
let yak_count: u32 = 3;
let span = expect::span().named("yak_shaving");
let (subscriber, handle) = subscriber::mock()
.new_span(
span.clone()
.with_fields(expect::field("number_of_yaks").with_value(&yak_count).only()),
)
.enter(span.clone())
.event(
expect::event().with_fields(
expect::field("number_of_yaks")
.with_value(&yak_count)
.and(expect::message("preparing to shave yaks"))
.only(),
),
)
.event(
expect::event().with_fields(
expect::field("all_yaks_shaved")
.with_value(&true)
.and(expect::message("yak shaving completed."))
.only(),
),
)
.exit(span.clone())
.only()
.run_with_handle();
with_default(subscriber, || {
yak_shaving(yak_count);
});
handle.assert_finished();
Supported Rust Versions
Tracing is built against the latest stable release. The minimum supported version is 1.63. The current Tracing version is not guaranteed to build on Rust versions earlier than the minimum supported version.
Tracing follows the same compiler support policies as the rest of the Tokio project. The current stable Rust compiler and the three most recent minor versions before it will always be supported. For example, if the current stable compiler version is 1.69, the minimum supported version will not be increased past 1.66, three minor versions prior. Increasing the minimum supported compiler version is not considered a semver breaking change as long as doing so complies with this policy.
License
This project is licensed under the MIT license.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tracing by you, shall be licensed as MIT, without any additional terms or conditions.