Helpers for making test assertions
## assert_contains
assert_contains(name, actual, expected, size, timeout)
Generates a test target which fails if the file doesn't contain the string.
Depends on bash, as it creates an sh_test target.
**PARAMETERS**
| Name | Description | Default Value |
| :------------- | :------------- | :------------- |
| name | target to create | none |
| actual | Label of a file | none |
| expected | a string which should appear in the file | none |
| size | the size attribute of the test target | None |
| timeout | the timeout attribute of the test target | None |