Writing tests

One test should only verify a single feature/method. I.e., one test for create_resource(), another for update_resource(), etc.

Negative tests

When writing negative tests, try to use the following format:

with pytest.raises(botocore.exceptions.ClientError) as exc:
err = exc.value.response["Error"]
# Use the pytest assert method, see https://docs.pytest.org/en/stable/how-to/assert.html#
assert err["Code"] == ..
assert err["Message"] == ..

This is the best way to ensure that exceptions are dealt with correctly by Moto.

ServerMode tests

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:

python moto/server.py
TEST_SERVER_MODE=true pytest -sv tests/test_service/..

Parallel tests

To speed up our CI, the tests for the awslambda, batch, ec2 and sqs services will run in parallel. This means the following:

  • Make sure you use unique names for functions/queues/etc

  • Calls to describe_reservations()/list_queues()/etc might return resources from other tests

Terraform tests

To verify that Moto behaves correctly, we run a subset of Terraform’s tests against the MotoServer to ensure it behaves the same as AWS does.

These tests will be run automatically for every PR, so you should not need to make any changes here.

A list of which tests currently pass against Moto can be found in tests/terraformtests/terraform-tests.success.txt.

Use the following commands to see the full list of available tests:

cd tests/terraformtests/terraform-provider-aws
# Choose the correct service in the next command - this example will list all tests for the ELB-service
go test ./internal/service/elb/ -v -list TestAcc

In order to check whether MotoServer behaves correctly against a specific test, you can use the following commands:

# Ensure you are back in the root-directory
# Start the MotoServer on port 4566
moto_server -p 4566
# Run the new tests
make terraformtests SERVICE_NAME=elb TEST_NAMES=NewTestName