Order (Processing) Out of Chaos

Awkwardness

We would really like to test our code, because it's interesting. Notice that the protocol has three interesting execution paths:

The session fails to start.
The session starts, but the customer doesn't have sufficient funds.
Billing is successful.

Billing


public class Billing
{
    private readonly CactusClient cactusClient;    public Billing()
    {
        cactusClient = new CactusClientImpl();
    }    public bool Bill(HolderInfo holderInfo, TransactionInfo[] transactions)
    {
        bool success = false;        if (cactusClient.StartSession(MERCHANT_ID))
        {
            cactusClient.SetHolderInfo(holderInfo);
            if (cactusClient.HasSufficientFundsFor(TotalAmountFor(transactions)))
            {
                for (int transaction = 0; transaction < transactions.Length; transaction++)
                    cactusClient.Process(transactions[transaction]);
                success = true;
            }
            cactusClient.StopSession();
        }
        return success;
    }
    …
}

Early in this album we showed you several forms of awkwardness. Which of the following forms are true for Billing's collaboration with CACTUS?

True

False

Awkward Setup: It's hard to cause CACTUS to fail the starting of the session.

Commentary

Indeed, the session might fail to start due to connectivity or load issues, which are very hard to simulate using the real thing.

(Reading...)

Awkward Setup: It's hard to set up a customer with insufficient funds.

Commentary

This is likely even impossible to do in code.

(Reading...)

Awkward Results: We can't trust CACTUS to always work properly, since it's not under our control.

Commentary

If CACTUS were unreliable, its CACTUS makers would probably go out of business. So it's OK to assume it's always there.

At Industrial Logic we use an internet-based service to process credit card payments. We've never seen it go down, although their test URL did a couple of times. Tracking down the failing test (we didn't fake the service at the time) took very little time, and order was soon restored.

(Reading...)

Awkward Runtime: Billing's tests will be slow.

Commentary

The tests access the internet, which is as slow as you can get in automated testing.

(Reading...)

Awkward Control: How do we actually verify that Billing calls the CACTUS API in the correct sequence?

Commentary

Well, really, how do we? Read on…

(Reading...)

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Faking & Mocking CSharp

Order (Processing) Out of Chaos

Awkwardness

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