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Urchin is a file-based test harness, normally used for testing shell programs. It is written in portable shell and should thus work on GNU/Linux, BSD (including Mac OS X), and other Unix-like platforms.

Urchin is called "Urchin" because sea urchins have shells called "tests".

Try it out

Urchin's tests are written in Urchin, so you can run them to see what Urchin is like. Clone the repository

git clone git://github.com/tlevine/urchin.git

Run the tests

cd urchin
./urchin tests

The above command will run the tests in your system's default shell, /bin/sh (on recent Ubuntu this is dash, but it could be ksh or bash on other systems); to test urchin's cross-shell compatibility, run this:

cd urchin
./cross-shell-tests

Install

Urchin is contained in a single file, so you can install it by copying it to a directory in your PATH. For example, you can run the following as root.

cd /usr/local/bin
wget https://raw.github.com/tlevine/urchin/master/urchin
chmod +x urchin

Urchin can be installed with npm too.

npm install -g urchin

Now you can run it.

urchin <test directory>

Run urchin -h to get command-line help.

Writing tests

Make a root directory for your tests. Inside it, put executable files that exit 0 on success and something else on fail. Non-executable files and hidden files (dotfiles) are ignored, so you can store fixtures right next to your tests. Run urchin from inside the tests directory.

Urchin only cares about the exit status, so you can actually write your tests in any language, not just shell.

More about writing tests

Tests are organized recursively in directories, where the names of the files and directories have special meanings.

tests/
  setup
  setup_dir
  bar/
    setup
    test_that_something_works
    teardown
  baz/
    jack-in-the-box/
      setup
      test_that_something_works
      teardown
    cat-in-the-box/
      fixtures/
        thingy.pdf
      test_thingy
  teardown

Directories are processed in a depth-first order. When a particular directory is processed, setup_dir is run before everything else in the directory, including subdirectories. teardown_dir is run after everything else in the directory.

A directory's setup file, if it exists, is run right before each test file within the particular directory, and the teardown file is run right after.

Files are only run if they are executable, and files beginning with . are ignored. Thus, fixtures and libraries can be included sloppily within the test directory tree. The test passes if the file exits 0; otherwise, it fails.

Tests files and subdirectories are run in ASCIIbetical order within each directory; that is, urchin looks for files within a directory in the following manner.

for file in *; do
  do_something_with_test_file $file
done

Writing cross-shell compatibility tests for testing shell code

While you could write your test scripts to explicitly invoke the functionality to test with various shells, Urchin facilitates a more flexible approach.

The specific approach depends on your test scenario:

• (a) Your test scripts invoke scripts containing portable shell code.
• (b) Your scripts source scripts containing portable shell code.

(a) Cross-shell tests with test scripts that invoke shell scripts

Urchin sets the TEST_SHELL environment variable so that you may change the shell with which your tests call other shell programs. To run your test scripts in multiple shells you must call $TEST_SHELL in your tests and then run urchin with the appropriate option.

In your test scripts, invoke the shell scripts to test via the shell specified in environment variable TEST_SHELL rather than directly; e.g.: $TEST_SHELL ../foo bar (rather than just ../foo bar).

On invocation of Urchin, prepend a definition of environment variable TEST_SHELL specifying the shell to test with, e.g.,

TEST_SHELL=zsh urchin ./tests

To test with multiple shells in sequence, use something like:

for shell in sh bash ksh zsh; do
  TEST_SHELL=$shell urchin ./tests
done

If TEST_SHELL has no value, Urchin defines it as /bin/sh, so the test scripts can rely on $TEST_SHELL always containing a value when Urchin runs them.

That said, we still recommand that you account for the possibility that $TEST_SHELL does not contain a value so that you may run your test scripts without Urchin. Supporting this case is very simple; when you invoke scripts that happen to be in the current directory, be sure to use the prefix ./, e.g., $TEST_SHELL ./baz rather than $TEST_SHELL baz.

(b) Cross-shell tests with test scripts that source shell scripts

If you source shell code in your test scripts, it is the test scripts themselves that must be run with the shell specified.

Urchin supports the -s <shell> option, which instructs Urchin to invoke the test scripts with the specified shell; e.g., -s bash.
(In addition, Urchin sets environment variable TEST_SHELL to the specified shell.)

Note that only test scripts that either have no shebang line at all or have shebang line #!/bin/sh are invoked with the specified shell. This allows non-shell test scripts or test scripts for specific shells to coexist with those whose invocation should be controlled by -s.

To test with multiple shells in sequence, use something like:

for shell in sh bash ksh zsh; do
  urchin -s $shell ./tests
done

Also consider using shall. It does something similar, but the interface may be more intuitive.

#!/usr/bin/env shall
echo This is a test file.

Alternatives to Urchin

Alternatives to Urchin are discussed in this blog post.

Ideas for new features

• Support Nagios plugins
• Stop running if a test fails so one can use Urchin as a setup framework.