```sh
test_directory directory [pattern]
```
This command can be used to run unit tests written in duckscript.<br>
It will run all duckscript files in the directory tree ending with **test.ds** and for each file, it will run
all functions that start with **test_**.<br>
Each such function is considered as a test and can run any type of code and check itself using assert commands.
### Parameters
* The root directory of all test files (all files ending with **test.ds** in the directory tree will be checked)
* Optional pattern for the file name or test function to limit invocation of only those tests.
### Return Value
**true** if successful.
### Examples
This is an example of a test function:
```sh
function test_set_get_unset
unset_env TEST_SET_GET_UNSET
value = get_env TEST_SET_GET_UNSET
assert_false ${value}
value = set_env TEST_SET_GET_UNSET "test value"
assert ${value}
value = get_env TEST_SET_GET_UNSET
assert_eq ${value} "test value"
end
```