https://github.com/akesson/tracing-collector

A tracing subscriber that collects a copy of the traces for use in tests with insta snapshots
https://github.com/akesson/tracing-collector

Last synced: 12 months ago
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A tracing subscriber that collects a copy of the traces for use in tests with insta snapshots

• Host: GitHub
• URL: https://github.com/akesson/tracing-collector
• Owner: akesson
• License: mit
• Created: 2023-02-04T17:38:48.000Z (over 3 years ago)
• Default Branch: main
• Last Pushed: 2023-02-06T08:50:22.000Z (over 3 years ago)
• Last Synced: 2025-04-13T00:43:57.013Z (about 1 year ago)
• Language: Rust
• Size: 6.84 KB
• Stars: 1
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

          
[![crates.io](https://img.shields.io/crates/v/tracing-collector)](https://crates.io/crates/tracing-collector)

# TracingCollector

`TracingCollector` creates a tracing subscriber that collects a copy of all traces into a buffer.

These traces can be retrieved by calling its Display implementation, i.e. calling `log.to_string()` or `format!("{log}")`.

This is useful for testing with [insta](https://crates.io/crates/insta) snapshots.

IMPORTANT! `TracingCollector` is meant for use when testing. It collects logs into a memory buffer

which keeps growing until it is read, the program exits or it is dropped. This means that if you are using `TracingCollector`

in production the program will eventually run out of memory.

When the `TracingCollector` is dropped, the buffer is emptied and the tracing subscriber is released but

the memory equivalent of a Mutex and an empty Vec is leaked.

When reading the traces, they are stripped of ANSI escape codes and prefixed with a `㏒` character. The former allows

the use of colored & formatted terminal output when the test fails or is run with `--nocapture` and the latter

makes the insta inline snapshots work since rust's `r###` raw string literals strips leading whitespace. The prefix can be

changed or removed using the `set_prefix` and `remove_prefix` methods.

## Example

```rust

#[test]

fn test_logs() {

    let log = TracingCollector::init_debug_level();

    tracing::info!("First log");

    insta::assert_display_snapshot!(log, @r###"

    ㏒   INFO  First log

        at tests/test.rs:6

    "###);

    tracing::debug!("Second log");

    tracing::info!("Third log");

    insta::assert_display_snapshot!(log, @r###"

    ㏒  DEBUG  Second log

        at tests/test.rs:14

      INFO  Third log

       at tests/test.rs:15

   "###);

}

```