README.md

Testing Functions

Of course you can test your code in your usual language specific ways, but we've also created a way to both define and test your functions, regardless of how or what language it is implemented in. This works by defining a series of inputs and expected outputs, essentially creating a contract for your function.

Test Format

The test format is simply a json file with an array of inputs and expected outputs. For example:

{
    "tests": [
        {
            "input": {
                "body": {
                    "name": "Johnny"
                }
            },
            "output": {
                "body": {
                    "message": "Hello Johnny"
                }
            }
        },
        {
            "input": {
                "body": ""
            },
            "output": {
                "body": {
                    "message": "Hello World"
                }
            }
        }
    ]
}

This is two tests, one with the input:

{
    "name": "Johnny"
}

And the other with an empty body. The expected outputs are:

{
    "message": "Hello Johnny"
}

and:

{
    "message": "Hello World"
}

respectively.

When you run fn test, it will run your function with the inputs provided and compare them against the expected outputs. If they don't match, it will fail.

Let's Try It

fn init --runtime go tester
cd tester
cat test.json

You'll see the same file as above.

Now run:

fn test

You should see the following results:

Test 1
PASSED -    ( 1.262317046s )

Test 2
PASSED -    ( 1.449515441s )

2 tests passed, 0 tests failed.

Add another test

Let's add another test to show you how it's done. Add the following test to test.json and save it:

{
    "input": {
        "body": {
            "name": "Jane"
        }
    },
    "output": {
        "body": {
            "message": "Hello Jane"
        }
    }
}

Now run fn test again. That's it!

Wrapping Up

Congratulations! In this tutorial you learned how to write function tests to ensure you don't break your function contract.

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