How to mock an AWS Lambda with moto-CodePudding

I created a code to invoke a AWS lambda function created somewhere else.

I would like to use moto for testing it, but I don't really understand how to do it and I continue to obtain errors.

This is a simple example of the main code:

import boto3
import json


class SimpleLambda:
    def __init__(self):
        self.aws_lambda = boto3.client("lambda", region_name="eu-west-2")

    def __call__(self):
        try:
            lambda_response = self.aws_lambda.invoke(
                FunctionName="test-lambda",
                Payload=json.dumps(
                    {
                        "Records": [
                            {
                                "Source": "test_source",
                                "Version": "test_version",
                            }
                        ]
                    }
                ),
            )
            return lambda_response["Payload"].read()
        except Exception as err:
            print(f"Could not invoke simple lambda: {err}")
            return None

and the test:

import os
import pytest
import unittest.mock as mock

import boto3
from moto import mock_lambda

from aws_lambda import SimpleLambda


@pytest.fixture
def aws_credentials():
    os.environ["AWS_ACCESS_KEY_ID"] = "testing"
    os.environ["AWS_SECRET_ACCESS_KEY"] = "testing"
    os.environ["AWS_SECURITY_TOKEN"] = "testing"
    os.environ["AWS_SESSION_TOKEN"] = "testing"


@pytest.fixture
def lambda_client(aws_credentials):
    with mock_lambda():
        yield boto3.client("lambda", region_name="eu-west-2")


@pytest.fixture
def lambda_test(lambda_client):
    lambda_client.create_function(
        FunctionName="test-lambda",
        Role="arn:aws:iam::123456789012:role/doesnotexist",
        Code={"ZipFile": b"test"}
    )
    yield


def test_simple_lambda_call(lambda_client, lambda_test):
    simple_lambda = SimpleLambda()

    test = simple_lambda()

I obtain the error:

botocore.errorfactory.InvalidParameterValueException: An error occurred (InvalidParameterValueException) when calling the CreateFunction operation: The role defined for the function cannot be assumed by Lambda.

I found several example about how to use moto with S3 bucket, but nothing with lambda.

Running the code in this other question, I obtain the same error.

Any advice?

CodePudding user response：

Moto also validates whether the IAM role exists, just like AWS does.

So make sure that the IAM role is created first:

with mock_iam():
    iam = boto3.client("iam", region_name="eu-west-2")
    iam_role = iam.create_role(
        RoleName="my-role",
        AssumeRolePolicyDocument="some policy",
        Path="/my-path/",
    )["Role"]["Arn"]