shpy

POSIX compliant^* spies and stubs for shell unit testing

ash	bash	dash	mksh	zsh

Features at a glance:

• Create spies for any command or function in the shell environment
• Stub the stdout, stderr, and return value of spies
• See the call count and check arguments passed to spies
• Integrates with the shunit2 testing framework

Table of Contents

• Why Unit Test Shell Scripts?
• Docker Image
• Usage
• Contributing
• API Reference
  • shunit2 Integration
• A Word On Shell Portability

Why Unit Test Shell Scripts?

Like other scripting languages, shell scripts can become complex and difficult to maintain over time. Unit tests help to avoid regressions and verify the correctness of functionality, but where do spies come in?

Spies are useful for limiting the dependencies and scope of a test. Code that utilizes system binaries or shell functions can be tested without running the underlying implementations, allowing tests to focus solely on the system under test. To see this in action, see examples/renamer

The benefits of spies are even greater when testing code that relies on a network. For an example of using spies to stub curl and make unit tests completely offline, see examples/coverfetch

Docker Image

Shpy is available as shpy/shpy on Docker Hub. The latest master node is published as shpy/shpy:latest, while tagged releases are available as shpy/shpy:1.0.0. To use kcov, append -kcov to the tag or use the kcov tag for the latest master node

To use the shpy image, mount your code into /app and specify the command you want to run. When using kcov, you can also mount /coverage and output your coverage reports to that directory

docker --rm -v$PWD:/app:ro shpy/shpy:1.0.0 zsh /app/tests/run_my_tests.sh
#           ^-your project                 ^--------your command---------

The following scripts and binaries are provided by this image

Usage

Let's try out shpy! If you don't want to install shpy locally you can run the official Docker image like so:

docker run -it --rm shpy/shpy:1.0.0

To use shpy, the SHPY_PATH environment variable must be set as the path to shpy and the shpy script must be sourced. If you're using the Docker image, SHPY_PATH is already set and shpy is located at /shpy/shpy

SHPY_PATH=path/to/shpy
. path/to/shpy

Let's create a spy for the touch command and call it!

createSpy touch
touch my-new-file
ls my-new-file # No such file or directory, touch wasn't actually called

The call to touch was stubbed out with a test dummy in place of the actual implementation. Spies record data about the calls made to them, allowing you to check the call count or call args

getSpyCallCount touch # 1
wasSpyCalledWith touch my-new-file # true
wasSpyCalledWith touch my-old-file # false
getArgsForCall touch 1 # my-new-file

Spies can also simulate successful or unsuccessful calls, like so:

createSpy -o 'call me once, shame on you' -e '' -r 0 \
          -e 'call me twice, shame on me' -o '' -r 1 touch
touch my-new-file # outputs "call me once, shame on you" to stdout, returns true
touch my-new-file # outputs "call me twice, shame on me" to stderr, returns false

When you're done playing with shpy, it's only polite to clean up after yourself

cleanupSpies
touch my-new-file
ls my-new-file # my-new-file, touch was actually called!

Your shell environment is back to normal, and you've got a new tool at your disposal! 🎓

Contributing

If you'd like to help with shpy's development, or just gain a better understanding of the internals, check out the contributor guidelines

API Reference

To use shpy in your tests, set SHPY_PATH to the location of shpy and source the script:

SHPY_PATH=path/to/shpy
export SHPY_PATH

. path/to/shpy

When using the Docker image, SHPY_PATH is preset as /shpy/shpy for convenience

The SHPY_VERSION environment variable is provided to get the current shpy version

A summary of functions:

shunit2 Integration

To use shpy asserts in your shunit2 tests, you must also source the shpy-shunit2 script:

. path/to/shpy
. path/to/shpy-shunit2

A summary of asserts:

Use the tearDown hook provided by shunit2 to remove all spies after each test

tearDown() {
  cleanupSpies
}

A Word On Shell Portability

shpy relies on portable but more modern shell features, such as the local keyword. To be clear, shpy does not use any Bashisms