To complete this walkthrough, you will need:

• Microsoft Dynamics NAV 2017 with a developer license.
  
• The CRONUS International Ltd. demo data company.
  

1. In the development environment, in Object Designer, create a new codeunit.

2. In the Properties window, in the Subtype field, select Test to specify that this is a test codeunit.

3. In the C/AL Globals window, on the Variables tab, enter the following variables.

   Name	DataType	Subtype
   RandomNumberGenerator	Codeunit	Random Number Generator
   LibraryPurchase	Codeunit	Library - Purchase
   Assert	Codeunit	Assert

   This adds 3 codeunits from the application test libraries as global variables so that you can use them in your test code.

4. In the C/AL Globals window, on the Text Constants tab, in the Name field, enter PurchInvDiscErr. In the ConstValue field, enter The Purchase Invoice Discount Amount was not calculated correctly.

5. In the C/AL Globals window, on the Functions tab, enter PurchInvDiscCalculationPInvAbove. This is the name of the test function.

   In this example, the name of the test function consists of the tested functionality, Purchase Invoice Discount Calculation, and relevant parameters that affect the test result. We recommend that you follow this naming pattern for your test functions also. In our example, the following parameters are introduced:

   • PInv for the document that is tested, purchase invoices. You can apply the same test to purchase orders or purchase credit memos. Also, we recommend that you have mirrored sets of tests for the sales area.
     
   • Above. It is a good practice to have tests for positive and negative scenarios. In this test, Isaac wants to check that discount come into effect when the document amount is above a minimum amount. But the amount in the document can be also less than or equal to the minimum amount.
     

6. On the Functions tab, choose Locals.

7. In the C/AL Locals window, on the Variables tab, enter the following variables, which you will use in the PurchInvDiscCalculationPInvAbove test function.

   Name	DataType	Subtype
   PurchLine	Record	Purchase Line
   MinAmount	Decimal
   DocAmount	Decimal
   DiscountPct	Decimal
   PurchCalcDisc	Codeunit	Purch.-Calc.Discount

   Important
   Make sure that you add these entries on the Variables tab, not on the Parameters tab. If you create them on the Parameters tab, you get an error when you compile that says the test method signature is invalid.

8. In the C/AL Editor, in the PurchInvDiscCalculationPInvAbove function, enter the following code:

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   // [SCENARIO] "Inv. Discount Amount" should be calculated on Purchase Invoice (in LCY), where Invoice amount is above the minimal amount required for invoice discount calculation. // [GIVEN] Vendor with invoice discount percentage "D" for minimal amount "A" in LCY // [GIVEN] Create purchase invoice with one line and amount >"A" DiscountPct := RandomNumberGenerator.RandDec(100,5); MinAmount := RandomNumberGenerator.RandDec(1000,2); DocAmount := MinAmount + RandomNumberGenerator.RandDec(100,2); CreatePurchDocument(PurchLine,PurchLine."Document Type"::Invoice,DocAmount,MinAmount,DiscountPct); // [WHEN] Calculate invoice discount for purchase document (line) PurchCalcDisc.RUN(PurchLine); // [THEN] "Inv. Discount Amount" = Amount "A" * discount "D" / 100 PurchLine.FIND; Assert.AreEqual(ROUND(PurchLine."Line Amount" * DiscountPct / 100),PurchLine."Inv. Discount Amount", PurchInvDiscErr);

   Isaac first defines the test scenario [SCENARIO], then details it with the GIVEN-THEN-WHEN notation. Finally, he adds the C/AL code.The code in this test function prepares the test data by setting a random discount percent, a minimum amount, and a document amount. Then, it creates a purchase document with a line and runs the Purch-Calc.Discount codeunit, which contains the code that is being tested. Finally, it verifies the results of running the Purch-Calc.Discount codeunit and raises an error if the results are not as expected.

   Isaac has created the test function. Next, he creates a helper function that generates data for the test.

1. In the C/AL Globals window, on the Functions tab, in the Name field, enter CreatePurchDocument.

2. In the Properties window for the new function, set the FunctionType property to Normal and the Local property to Yes.

3. In the C/AL Locals window for the CreatePurchDocument function, on the Parameters tab, enter the following parameters.

   Var	Name	DataType	Subtype
   Yes	PurchLine	Record	Purchase Line
   	DocumentType	Option
   	DocAmount	Decimal
   	MinAmount	Decimal
   	DiscountPct	Decimal

4. In the C/AL Locals window, on the Variables tab, enter the following variables.

   Name	DataType	Subtype	Length
   VendorInvoiceDisc	Record	Vendor Invoice Disc.
   PurchaseHeader	Record	Purchase Header
   VendorNo	Code		20

5. In the C/AL Editor, in the CreatePurchDocument function, enter the following code.

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   // Create vendor VendorNo := LibraryPurchase.CreateVendorNo; // Create vendor invoice discount VendorInvoiceDisc.INIT; VendorInvoiceDisc.Code := VendorNo; VendorInvoiceDisc.VALIDATE("Currency Code",''); VendorInvoiceDisc.VALIDATE("Minimum Amount",MinAmount); VendorInvoiceDisc.VALIDATE("Discount %", DiscountPct); VendorInvoiceDisc.INSERT(TRUE); // Create purchase line LibraryPurchase.CreatePurchaseDocumentWithItem(PurchaseHeader,PurchaseLine,DocumentType,VendorNo,'',1,'',0D); PurchaseLine.VALIDATE("Direct Unit Cost",DocAmount); PurchaseLine.MODIFY(TRUE);

   The code in this helper function prepares data for the test by creating a new vendor, setting up the invoice discount, and creating a purchase document with an item. Because this helper function is not specific to the test itself, Isaac can reuse it for similar tests. For example, he can call it with other parameters and create a purchase credit memo, or set up 0% discount, or create a document where the total amount is less than the minimum amount that is specified in Vendor Invoice Disc. table.

   Note
   This test code does not guarantee that the state of the database after you run the test is the same as the state of the database before you run the test.

6. On the File menu, choose Save.

7. In the Save As window, in the ID field, enter 50005. In the Name field, enter ERM Vendor Discount. Verify that the Compiled check box is selected, and then choose the OK button.