选题[tech]: 20210204 How to implement business requirements in software development

sources/tech/20210204 How to implement business requirements in software development.md

sources/tech/20210204 How to implement business requirements in software development.md

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+[#]: collector: (lujun9972)
+[#]: translator: ( )
+[#]: reviewer: ( )
+[#]: publisher: ( )
+[#]: url: ( )
+[#]: subject: (How to implement business requirements in software development)
+[#]: via: (https://opensource.com/article/21/2/exceptional-behavior)
+[#]: author: (Alex Bunardzic https://opensource.com/users/alex-bunardzic)
+
+How to implement business requirements in software development
+======
+Increment your e-commerce app to ensure it implements required business
+process rules correctly.
+![Working on a team, busy worklife][1]
+
+In my previous articles in this series, I explained why tackling coding problems all at once, as if they were hordes of zombies, is a mistake. I'm using a helpful acronym to explain why it's better to approach problems incrementally. **ZOMBIES** stands for:
+
+**Z** – Zero
+**O** – One
+**M** – Many (or more complex)
+**B** – Boundary behaviors
+**I** – Interface definition
+**E** – Exercise exceptional behavior
+**S** – Simple scenarios, simple solutions
+
+In the first three articles in this series, I demonstrated the first five **ZOMBIES** principles. The first article [implemented **Z**ero][2], which provides the simplest possible path through your code. The second article performed [tests with **O**ne and **M**any][3] samples, and the third article looked at [**B**oundaries and **I**nterfaces][4]. In this article, I'll take a look at the penultimate letter in our acronym: **E**, which stands for "exercise exceptional behavior."
+
+### Exceptional behavior in action
+
+When you write an app like the e-commerce tool in this example, you need to contact product owners or business sponsors to learn if there are any specific business policy rules that need to be implemented.
+
+Sure enough, as with any e-commerce operation, you want to put business policy rules in place to entice customers to keep buying. Suppose a business policy rule has been communicated that any order with a grand total greater than $500 gets a percentage discount.
+
+OK, time to roll up your sleeves and craft the executable expectation for this business policy rule:
+
+
+```
+[Fact]
+public void Add2ItemsTotal600GrandTotal540() {
+        var expectedGrandTotal = 540.00;
+        var actualGrandTotal = 0.00;
+        Assert.Equal(expectedGrandTotal, actualGrandTotal);
+}
+```
+
+The confirmation example that encodes the business policy rule states that if the order total is $600.00, the `shoppingAPI` will calculate the grand total to discount it to $540.00. The script above fakes the expectation just to see it fail. Now, make it pass:
+
+
+```
+[Fact]
+public void Add2ItemsTotal600GrandTotal540() {
+        var expectedGrandTotal = 540.00;
+        Hashtable item = [new][5] Hashtable();
+        item.Add("00000001", 200.00);
+        shoppingAPI.AddItem(item);
+        Hashtable item2 = [new][5] Hashtable();
+        item2.Add("00000002", 400.00);
+        shoppingAPI.AddItem(item2);
+        var actualGrandTotal = shoppingAPI.CalculateGrandTotal();
+        Assert.Equal(expectedGrandTotal, actualGrandTotal);
+}
+```
+
+In the confirmation example, you are adding one item priced at $200 and another item priced at $400 for a total of $600 for the order. When you call the `CalculateGrandTotal()` method, you expect to get a total of $540.
+
+Will this microtest pass?
+
+
+```
+[xUnit.net 00:00:00.57] tests.UnitTest1.Add2ItemsTotal600GrandTotal540 [FAIL]
+  X tests.UnitTest1.Add2ItemsTotal600GrandTotal540 [2ms]
+  Error Message:
+   Assert.Equal() Failure
+Expected: 540
+Actual: 600
+[...]
+```
+
+Well, it fails miserably. You were expecting $540, but the system calculates $600. Why the error? It's because you haven't taught the system how to calculate the discount on order totals larger than $500 and then subtract that discount from the grand total.
+
+Implement that processing logic. Judging from the confirmation example above, when the order total is $600.00 (which is greater than the business rule threshold of an order totaling $500), the expected grand total is $540. This means the system needs to subtract $60 from the grand total. And $60 is precisely 10% of $600. So the business policy rule that deals with discounts expects a 10% discount on all order totals greater than $500.
+
+Implement this processing logic in the `ShippingAPI` class:
+
+
+```
+private double Calculate10PercentDiscount(double total) {
+        double discount = 0.00;
+        if(total > 500.00) {
+                discount = (total/100) * 10;
+        }
+        return discount;
+}
+```
+
+First, check to see if the order total is greater than $500. If it is, then calculate 10% of the order total.
+
+You also need to teach the system how to subtract the calculated 10% from the order grand total. That's a very straightforward change:
+
+
+```
+`return grandTotal - Calculate10PercentDiscount(grandTotal);`
+```
+
+Now all tests pass, and you're again enjoying steady success. Your script **Exercises exceptional behavior** to implement the required business policy rules.
+
+### One more to go
+
+I've taken us to **ZOMBIE** now, so there's just **S** remaining. I'll cover that in the exciting series finale.
+
+--------------------------------------------------------------------------------
+
+via: https://opensource.com/article/21/2/exceptional-behavior
+
+作者：[Alex Bunardzic][a]
+选题：[lujun9972][b]
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://opensource.com/users/alex-bunardzic
+[b]: https://github.com/lujun9972
+[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/team_dev_email_chat_video_work_wfm_desk_520.png?itok=6YtME4Hj (Working on a team, busy worklife)
+[2]: https://opensource.com/article/21/1/zombies-zero
+[3]: https://opensource.com/article/21/1/zombies-2-one-many
+[4]: https://opensource.com/article/21/1/zombies-3-boundaries-interface
+[5]: http://www.google.com/search?q=new+msdn.microsoft.com