Crate snapshot_testing 

snapshot-testing

Assert that strings equal easily updatable snapshot files. Show nice colored diffs if not.

Usage Example

/// Regression test for `impl Display` of a complex type.
#[test]
fn test_display_of_some_type() {
    let value = ... // produce a value somehow

    snapshot_testing::assert_eq_or_update(
        value.to_string(),
        "./tests/snapshots/display-impl.txt",
    );
}

# Create (or update) the snapshot file
UPDATE_SNAPSHOTS=yes cargo test

# Ensure the Display impl is not accidentally changed
cargo test

Diffing Engine

We use the excellent insta diffing engine without suffering from Issue #425: GitHub syntax highlights insta snapshots like Jest Snapshots which unfortunately makes diffs very hard to read.

Audit the Code

This crate is very small and easily audited with the following command ¹:

curl -H "User-Agent: $USER at $HOST" \
     -L https://crates.io/api/v1/crates/snapshot-testing/0.1.8/download |
tar --extract --gzip --to-stdout |
less

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1. Please also see crates.io Data Access Policy. ↩

Functions

assert_eq_or_update

Assert that value equals the snapshot at snapshot_path. If there is a mismatch the function will panic with a helpful diff that shows what changed.