Test class coverage using asserts

Question

I am facing a bizarre situation where test class coverage is 100% irrespective of how much logic is implemented in the test class. Below is the class

public with sharing class testconstants{
  public static string str1 ='firststring';
  public string str2='secondstring';
  public string str3='thirdstring';
}

The test class is

@isTest
public class testcontants_testclass{
  static testmethod void method1()
  {
    testconstants t = new testconstants();
    test.starttest();
    system.assertEquals(testconstants.str1,'firststring');
    test.stoptest();
  }
}

Now even if I am keeping two asserts (one for str1 and other for str2) or only one assert (as above) , the coverage is reaching 100%.

Answer 1

The coverage is not calculated based upon the Asserts. Asserts just used to check the functionality.

Answer 2

Coverage is calculated by the lines of code that your unit tests traverse (or "cover").

I think that, when your tests reference the testconstants, the class is loaded in memory and all the statics are initialized/brought into place (at least, that's how it would work in Java, and I assume Apex is similar). At that point, all your static members are covered.

If you added static and/or instance methods, you would need to call them to give them coverage.

I'm sure there are different opinions on what's best practice when testing a class that contains just constants. I prefer to test business behaviour rather than implementation details (see this excellent presentation by Ian Cooper). Unless those constants had some business value, I would simply not test that class.

Answer 3

Asserts are used to check whether you are getting the expected output at that point.