How to write unit test for aws lambda handler function (Python)

Question

Everyone

I have a function which is the handler for aws lambdafunction.

def data_list(event, data_subject):
    dynamodb = boto3.resource("dynamodb")
    table = dynamodb.Table("TestTable")
    print("DATA_LIST")

    def get_col_name(data_subject):
        if data_subject == "X":
            return 'something'
        elif data_subject == "y":
            return 'some other things'
        elif data_subject == "c":
            return 'really'

    def another_function(var):
        pass

I have multiple function under data_list function how can we write unittest cases for each individual function which is under data_list function

Alan · Accepted Answer · 2021-02-27 14:35:47Z

3

Don't.

Instead move them out from the lambda handler function so that you can test them entirely separately.

Then make the lambda handler function it's self so small and simple that you barely need to test it, and can handle testing it with system tests.

answered Feb 27, 2021 at 14:35

Alan

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2 Comments

Amit Over a year ago

is there any way to still do it ?

Alan Over a year ago

I hate to be that guy who asks this, but: why would you want to? Unit tests should be used to test "business logic" - think "the public-ish interface to the code". They shouldn't be used to test internal implementation details, because that way when you change said implementation, you break all the tests. Nested functions fall under the category of internal implementation details typically. For this not to be the case you would have to have a very special case, that you would need to explain in your question.

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