Moto has a [Code of Conduct](https://github.com/spulec/moto/blob/master/CODE_OF_CONDUCT.md), you can expect to be treated with respect at all times when interacting with this project.
Moto has a [Makefile](./Makefile) which has some helpful commands for getting set up.
You should be able to run `make init` to install the dependencies and then `make test` to run the tests.
*NB. On first run, some tests might take a while to execute, especially the Lambda ones, because they may need to download a Docker image before they can execute.*
- A dedicated TaggingService exists in `moto.utilities`, to help with storing/retrieving tags for resources. Not all services use it yet, but contributors are encouraged to use the TaggingService for all new features.
- Our CI runs all tests twice - one normal run, and one run in ServerMode. In ServerMode, Moto is started as a stand-alone Flask server, and all tests are run against this Flask-instance.
To verify whether your tests pass in ServerMode, you can run the following commands:
- When writing tests, one test should only verify a single feature/method. I.e., one test for `create_resource()`, another for `update_resource()`, etc.
- When writing negative tests, try to use the following format:
```
with pytest.raises(botocore.exceptions.ClientError) as exc:
client.failing_call(..)
err = exc.value.response["Error"]
# These assertions use the 'sure' library, but any assertion style is accepted
err["Code"].should.equal(..)
err["Message"].should.equal(..)
```
This is the best way to ensure that exceptions are dealt with correctly by Moto.
- If a service is only partially implemented, a warning can be used to inform the user. For instance:
```
import warnings
warnings.warn("The Filters-parameter is not yet implemented for client.method()")
Moto is easier to contribute to than you probably think. There's [a list of which endpoints have been implemented](https://github.com/spulec/moto/blob/master/IMPLEMENTATION_COVERAGE.md) and we invite you to add new endpoints to existing services or to add new services.
* Search for an existing [issue](https://github.com/spulec/moto/issues) that matches what you want to achieve.
* If one doesn't already exist, create a new issue describing what's missing. This is where we'll all talk about the new addition and help you get it done.
* Create a [pull request](https://help.github.com/articles/using-pull-requests/) and mention the issue # in the PR description.
* Try to add a failing test case. For example, if you're trying to implement `boto3.client('acm').import_certificate()` you'll want to add a new method called `def test_import_certificate` to `tests/test_acm/test_acm.py`.
* Implementing the feature itself can be done by creating a method called `import_certificate` in `moto/acm/responses.py`. It's considered good practice to deal with input/output formatting and validation in `responses.py`, and create a method `import_certificate` in `moto/acm/models.py` that handles the actual import logic.
* If you can also implement the code that gets that test passing then great! If not, just ask the community for a hand and somebody will assist you.
Implementing a new service from scratch is more work, but still quite straightforward. All the code that intercepts network requests to `*.amazonaws.com` is already handled for you in `moto/core` - all that's necessary for new services to be recognized is to create a new decorator and determine which URLs should be intercepted.
Note the `urls.py` that redirects all incoming URL requests to a generic `dispatch` method, which in turn will call the appropriate method in `responses.py`.
If you want more control over incoming requests or their bodies, it is possible to redirect specific requests to a custom method. See this PR for an example: https://github.com/spulec/moto/pull/2957/files
By using `scripts/scaffold.py`, you can automatically generate template code of new services and new method of existing service. The script looks up API specification of given boto3 method and adds necessary codes including request parameters and response parameters. In some cases, it fails to generate codes.
Please try out by running `python scripts/scaffold.py`
