parametrized-tests.md

Parametrized tests

Goal for this training chapter

• you know what parametrized tests are
• you know how you can add further test cases to parametrized tests
• you've seen how parametrized tests are look like
• you can add further test cases to parametrized tests
• you're able to handle a failed test
• you've can use explicit type conversion

What are parametrized tests?

1. In some cases you want to test a functions or method with different input parameters. This can be solved in this way:

   USING Axunit.Assert;
   USING Simatic.Ax.Tutorial;
   
   NAMESPACE Tutorial.Test
   
       {TestFixture}
       CLASS Test_Add
   
           {Test}
           METHOD PUBLIC Test_values
               VAR_TEMP
                   result : DINT;
               END_VAR
               Add(v1 := 1, v2 := 1 , result => result);
               Equal(2, result);                   
   
               Add(v1 := -1, v2 := -1 , result => result);
               Equal(DINT#-2, result);            
   
               Add(v1 := 1, v2 := -1 , result => result);
               Equal(DINT#0, result);            
   
               Add(v1 := -1, v2 := 1 , result => result);
               Equal(DINT#0, result);            
           END_METHOD
       END_CLASS    
   
   END_NAMESPACE
   

   you'll find the code in the file test/Test_Add.st

   In this case, the Add function will be tested with the input parameter:

   Test#	v1	v2	expected result
   1.	1	1	2
   2.	-1	-1	-2
   3.	1	-1	0
   3.	-1	1	0

   Another solution are parametrized tests

2. Open the file Test_Add_Parametrized.st

3. Uncomment all the code by pressing STRG + a (select all) and then STRG + # (uncomment all)

   

   Here you see, that the test pragma can also have some parameters. The parameters i1, i2, res will be forwarded to the input variables i1, i2, res of the method Test_values

4. Execute the tests

   In the test explorer you can see, that the test is executed four times with different parameters.

   

Add further test parameter to the parametrized test

1. If not, open the file Test_Add_Parametrized.st

2. Extend the parametrized test by another test case with the values i1 := 32000, i2 := 32000, and res := DINT#32000

   Your test configuration should be look like:

   

3. Execute the test

   Result: you'll get a failed test.

   

   The test shows you, that your expected value 64000 does not match the acual value -1536

4. hover over the failed test in the explorer and click on Go to Test. The test file will be opened.

   

5. Press CTRL hover over the Add function. The Add method will be underlined. Click left to jump the Add function

   

Explicit type conversion

1. The problem for our failed test was obviously an integer overflow. Why can I say this? Because I know it.

   A look in line 13 will explain this:

   result := v1 + v2;
   

   v1and v2are of the type INT. When we add 32000 + 32000, the addition will be done as an integer operation, where the maximum value is 32767. To solve this, we've to convert the INT to DINT explicitly.

2. Replace the line 13 in the file by

   result := TO_DINT(v1) + TO_DINT(v2);
   

   The integer values will be converted to double integer values

3. Run the tests again

   The tests should now run without errors

Summary

Goal reached? Check yourself...

• you know what parametrized tests are ✔
• you know how you can add further test cases to parametrized tests ✔
• you've seen how parametrized tests are look like ✔
• you can add further test cases to parametrized tests ✔
• you're able to handle a failed test ✔
• you've can use explicit type conversion ✔

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