Stubbing file tests in shUnit2

Question

I am using shUnit2 to do unit testing in Bash shell scripts.

I have code like this:

if [ ! -x /usr/local/rvm/bin/rvm ]; then
  ...
fi

etc

I want to write unit tests to test this code, but to do that I need to stub out the behaviour of Bash file tests.

One way I could do this would be to refactor as:

if ! test -x /usr/local/rvm/bin/rvm; then
  ...
fi

Then I can stub out the test built-in using something like:

test() {
  case "$*" in
  "-x /usr/local/rvm/bin/rvm")
    false
    ;;
  esac
}

Creating the files that are expected during setUp might be an option sometimes, but obviously not always.

Or, I could refactor to move file tests inside custom functions, e.g.

rvm_installed() {
  [ -x /usr/local/rvm/bin/rvm ]
}

Then I can stub this function in my tests.

Is there any way to test this code without refactoring it though?

score 2 · Answer 1 · answered Jul 02 '17 at 11:02

2

You can stub [ just as you can stub test:

[() {
  case "$*" in
  "-x /usr/local/rvm/bin/rvm")
    false
    ;;
  esac
}

answered Jul 02 '17 at 11:02

janos

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Wow. I never would have guessed you could do that. – Alex Harvey Jul 02 '17 at 11:26
Actually, as clever as this is, stubbing [ breaks shUnit2. – Alex Harvey Jul 02 '17 at 16:13
@AlexHarvey ouch. By the same logic, perhaps you cannot stub anything that might be used by `shUnit2` ? They could protect against that by using `command [` everywhere instead of `[` – janos Jul 02 '17 at 16:20
Yes, why not? I might see if there is some way to patch it. – Alex Harvey Jul 02 '17 at 17:14

Alex Harvey · Accepted Answer · 2017-12-09T13:43:27.100

What @janos said is correct, but it breaks shUnit2 if something like [ is stubbed.

I raised a pull request that was merged to fix this problem in the way @janos suggested in the comments. This fix will hopefully be released eventually in shUnit2 2.1.7.

In the mean time the options are:

1) Use the patched version above.

2) See also suggestions about how to use a wrapper file in this example here: https://github.com/zofrex/bourne-shell-unit-testing

Stubbing file tests in shUnit2

2 Answers2