test-env-log
test-env-log is a crate that takes care of automatically initializing logging and/or tracing for Rust tests.
When running Rust tests it can often be helpful to have easy access to
the verbose log messages emitted by the code under test. Commonly, these
log messages may be coming from the log
crate or being emitted
through the tracing
infrastructure.
The problem with either -- in the context of testing -- is that some form of initialization is required in order to make these crate's messages appear on a standard output stream.
The commonly used env_logger
(which provides an easy way to configure log
based logging), for
example, needs to be initialized like this:
let _ = builder.is_test.try_init;
in each and every test.
Similarly, tracing
based solutions require a subscriber to be
registered that writes events/spans to the console.
This crate takes care of this per-test initialization in an intuitive way.
Usage
The crate provides a custom #[test]
attribute that, when used for
running a particular test, takes care of initializing log
and/or
tracing
beforehand.
Example
As such, usage is as simple as importing and using said attribute:
use test;
It is of course also possible to initialize logging for a chosen set of tests, by only annotating these with the custom attribute:
Logging Configuration
As usual when running cargo test
, the output is captured by the
framework by default and only shown on test failure. The --nocapture
argument can be supplied in order to overwrite this setting. E.g.,
Furthermore, the RUST_LOG
environment variable is honored and can be
used to influence the log level to work with (among other things).
Please refer to the env_logger
docs for more
information.
Features
The crate comes with two features:
log
, enabled by default, controls initialization for thelog
crate.trace
, disabled by default, controls initialization for thetracing
crate.
Depending on what backend the crate-under-test (and its dependencies) use, the respective feature should be enabled to make messages that are emitted by the test manifest on the console.
Note that as a user you are required to explicitly add env_logger
or
tracing-subscriber
as a dependency to your project-under-test (when
enabling the log
or trace
feature, respectively). E.g.,
[]
= "*"
= { = "0.2", = ["chrono", "env-filter", "fmt"]}