Crate snapbox 

Snapshot testing toolbox

When you have to treat your tests like pets, instead of cattle

snapbox is a snapshot-testing toolbox that is ready to use for verifying output from

• Function return values
• CLI stdout/stderr
• Filesystem changes

It is also flexible enough to build your own test harness like trycmd.

Which tool is right

• cram: End-to-end CLI snapshotting agnostic of any programming language
  • See also scrut
• trycmd: For running a lot of blunt tests (limited test predicates)
  • Particular attention is given to allow the test data to be pulled into documentation, like with mdbook
• tryfn: For running a lot of simple input/output tests
• snapbox: When you want something like trycmd in one off cases or you need to customize trycmds behavior.
• assert_cmd + assert_fs: Test cases follow a certain pattern but special attention is needed in how to verify the results.
• Hand-written test cases: for peculiar circumstances

Getting Started

Testing Functions:

• assert_data_eq! for quick and dirty snapshotting

Testing Commands:

• cmd::Command: Process spawning for testing of non-interactive commands
• cmd::OutputAssert: Assert the state of a Command’s Output.

Testing Filesystem Interactions:

• dir::DirRoot: Working directory for tests
• Assert: Diff a directory against files present in a pattern directory

You can also build your own version of these with the lower-level building blocks these are made of.

Examples

assert_data_eq!

snapbox::assert_data_eq!("Hello many people!", "Hello [..] people!");

Assert

let actual = "...";
snapbox::Assert::new()
    .action_env("SNAPSHOTS")
    .eq(actual, snapbox::file!["help_output_is_clean.txt"]);

Modules

assert

cmd

Run commands and assert on their behavior

data

actual and expected Data for testing code

dir

Initialize working directories and assert on how they’ve changed

filter

Filter actual or expected Data

prelude

Easier access to common traits

report

Utilities to report test results to users

utils

Macros

assert_data_eq

Check if a value is the same as an expected value

debug

Feature-flag controlled additional test debug information

file

Declare an expected value for an assert from a file

str

Declare an expected value from within Rust source

Structs

Assert

Snapshot assertion against a file’s contents

Data

Test fixture, actual output, or expected result

RedactedValue

Redactions

Replace data with placeholders

Traits

IntoData

Convert to Data with modifiers for expected data

IntoJson

Capture the serde representation of a value

ToDebug

Capture the pretty debug representation of a value

Functions

assert_subset_eq

Check if a path matches the content of another path, recursively

assert_subset_matches

Check if a path matches the pattern of another path, recursively