write-tests.md

Write own unit tests with AxUnit

Goal for this training chapter

After this training session:

• you know how a test class looks like
• you know how you create a test method within a test class
• you know what are assertions and how they're used
• use full qualified type identifier for items in namespaces
• you know, where you find information for writing test functions
• you know where you find guidelines and tips for writing tests

Create a test for the new implemented class valve

1. Open the file Test_Valve.st in the folder test

   

   Here you can see a template for a test class. It's marked with the pragma {TestFixture}

   Tip: You can filter the files in the Explorer:

   

   More information you'll find here

   AxUnit support not just test classes. It supports also test functions

2. Insert a test method. By entering te the snippet test-method will be proposed. And press enter

   

   Test methods will be marked with the pragma {Test}

   

3. Change the name of the method to Test_Open_valve_and_Expect_IsOpen_True

   Recommendations for writing tests, you'll find here

4. In the next step we select our class we want to test. Therefore we declare the variable v in the VAR section

   VAR PRIVATE
       v : Simatic.Ax.Tutorial.Valve;
   END_VAR
   

   In this case we use the full qualified name for the Valve class. This is an alternative to USING Simatic.Ax.Tutorial;.

5. To implement the test itself, we modify the method MyTestMethod in this way:

   {Test}
   METHOD PUBLIC Test_Open_valve_and_Expect_IsOpen_True
       v.Open();
       AxUnit.Assert.Equal(actual := v.IsOpen(), expected := TRUE);
   END_METHOD
   

   Explanation:

   1. The method v.Open() calls the method Open of the class valve. In this case we expect, that the method IsOpen() returns the value TRUE

   2. The expression Equal(actual := v.IsOpen(), expected := TRUE); contains the assertion Equal which check if the returned value of IsOpen() equals TRUE.

      Further assertions are:

      • NotEqual
      • LessThan
      • GreaterThan

      More information regarding testing, you'll find here

Summary

Goal reached? Check yourself...

• you know how a test class looks like ✔
• you know how you create a test method within a test class ✔
• you know what are assertions and how they're used ✔
• use full qualified type identifier for items in namespaces ✔
• you know, where you find information for writing test functions ✔
• you know where you find guidelines and tips for writing tests ✔