Test an Asset Compute worker

The Asset Compute project defines a pattern for easily creating and executing tests of Asset Compute workers.

Anatomy of a worker test

Asset Compute workers’ tests are broken into test suites, and within each test suite, one or more test cases asserting a condition to test.

The structure of tests in an Asset Compute project are as follows:


/actions/<worker-name>/index.js
...
/test/
  asset-compute/
    <worker-name>/           <--- Test suite for the worker, must match the yaml key for this worker in manifest.yml
        <test-case-1>/       <--- Specific test case
            file.jpg         <--- Input file (ie. `source.path` or `source.url`)
            params.json      <--- Parameters (ie. `rendition.instructions`)
            rendition.png    <--- Expected output file (ie. `rendition.path`)
        <test-case-2>/       <--- Another specific test case for this worker
            ...

Each test cast can have the following files:

file.<extension>
- Source file to test (extension can be anything except .link)
- Required
rendition.<extension>
- Expected rendition
- Required, except for error testing
params.json
- The single rendition JSON instructions
- Optional
validate
- A script that gets expected and actual rendition file paths as arguments and must return exit code 0 if the result is ok, or a non-zero exit code if the validation or comparison failed.
- Optional, defaults to the diff command
- Use a shell script that wraps a docker run command for using different validation tools
mock-<host-name>.json
- JSON formatted HTTP responses for mocking external service calls.
- Optional, only used if the worker code makes HTTP requests of its own

Writing a test case

This test case asserts the parameterized input (params.json) for the input file (file.jpg) generates the expected PNG rendition (rendition.png).

First delete the auto-generated simple-worker tests case at /test/asset-compute/simple-worker as this is invalid, as our worker no longer simply copies the source to the rendition.
Create a new test case folder at /test/asset-compute/worker/success-parameterized to test a successful execution of the worker that generates a PNG rendition.
In the success-parameterized folder, add the test input file for this test case and name it file.jpg.
In the success-parameterized folder, add a new file named params.json that defines the input parameters of the worker:
```
{
    "size": "400",
    "contrast": "0.25",
    "brightness": "-0.50"
}
```
These are the same key/values passed into the Development Tool’s Asset Compute profile definition, less the worker key.
Add the expected rendition file to this test case and name it rendition.png. This file represents the expected output of the worker for the given input file.jpg.
From the command line, run the tests the project root by executing aio app test
- Ensure Docker Desktop and supporting Docker images are installed and started
- Terminate any running Development Tool instances

Test - Success

Writing an error checking test case

This test case tests to ensure the worker throws the appropriate error when the contrast parameter is set to an invalid value.

Create a new test case folder at /test/asset-compute/worker/error-contrast to test a erring execution of the worker due to an invalid contrast parameter value.
In the error-contrast folder, add the test input file for this test case and name it file.jpg. The contents of this file is immaterial to this test, it just needs to exist to get past the “Corrupt source” check, in order to reach the rendition.instructions validity checks, that this test case validates.
In the error-contrast folder, add a new file named params.json that defines the input parameters of the worker with the contents:
```
{
    "contrast": "10",
    "errorReason": "rendition_instructions_error"
}
```
- Set contrast parameters to 10, an invalid value, as contrast must be between -1 and 1, to throw a RenditionInstructionsError.
- Assert the appropriate error is thrown in tests by setting the errorReason key to the “reason” associated with the expected error. This invalid contrast parameter throws the custom error, RenditionInstructionsError, therefore set the errorReason to this error’s reason, orrendition_instructions_error to assert it is thrown.
Since no rendition should be generated during an erring execution, no rendition.<extension> file is necessary.
Run the test suite from the root of the project by executing the command aio app test
- Ensure Docker Desktop and supporting Docker images are installed and started
- Terminate any running Development Tool instances