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@@ -19,6 +19,7 @@ test helper libraries written for [Bats][bats]. Features: - [error reporting](#error-reporting) - [output formatting](#output-formatting) +- [language tools](#language-and-execution) See the [shared documentation][bats-docs] to learn how to install and load this library. @@ -121,6 +122,66 @@ actual (3 lines): -- ``` +## Language and Execution + +### Restricting invocation to specific locations + +Sometimes a helper may work properly only when called from a certain +location. Because it depends on variables to be set or some other side +effect. + +A good example is cleaning up temporary files only if the test has +succeeded. The outcome of a test is only available in `teardown`. Thus, +to avoid programming mistakes, it makes sense to restrict such a +clean-up helper to that function. + +`batslib_is_caller` checks the call stack and returns `0` if the caller +was invoked from a given function, and `1` otherwise. This function +becomes really useful with the `--indirect` option, which allows calls +through intermediate functions, e.g. the calling function may be called +from a function that was called from the given function. + +Staying with the example above, the following code snippet implements a +helper that is restricted to `teardown` or any function called +indirectly from it. + +```shell +clean_up() { + # Check caller. + if batslib_is_caller --indirect 'teardown'; then + echo "Must be called from \`teardown'" \ + | batslib_decorate 'ERROR: clean_up' \ + | fail + return $? + fi + + # Body goes here... +} +``` + +In some cases a helper may be called from multiple locations. For +example, a logging function that uses the test name, description or +number, information only available in `setup`, `@test` or `teardown`, to +distinguish entries. The following snippet implements this restriction. + +```shell +log_test() { + # Check caller. + if ! ( batslib_is_caller --indirect 'setup' \ + || batslib_is_caller --indirect "$BATS_TEST_NAME" \ + || batslib_is_caller --indirect 'teardown' ) + then + echo "Must be called from \`setup', \`@test' or \`teardown'" \ + | batslib_decorate 'ERROR: log_test' \ + | fail + return $? + fi + + # Body goes here... +} +``` + + <!-- REFERENCES --> [bats]: https://github.com/sstephenson/bats |