全班学习单元测试

Question

I'm currently looking into unit testing but not quite sure how full branch and class coverage can be achieved.

Given the following class:

public class foo
{

  public int multiply(int a, int b)
  {
      int returnVal = 0;
      if(a==0 || b == 0)
      {
         return returnVal;
      }
      if(a==1)
      {
        return b;
      }
      else if(b==1)
      {
         return a;
      }
      for(int i = 0; i < a; i++)
      {
         returnVal += b;
      }
}

What could I do to the above code to make it 100% branch coverage capable?

Answer 1

What could I do to the above code to make it 100% branch coverage capable?

If I've read your code correctly, then you don't need to change it. If you want 100% coverage, you just need to design the test cases appropriately.

(Hint: if I've counted correctly, you can get 100% coverage with a set of 5 test cases ...)

Answer 2

You can cover all your code with 5 unit tests.

Tests

when a = 0

multiply(0, 13) must return 0

when b = 0

multiply(13, 0) must return 0

when a = 1

multiply(1, 13) must return 13

when b = 1

multiply(13, 1) must return 13

nominal case

multiply(5, 4) must return 20

Tip

Note that with Junit you can use parameterized tests .

Answer 3

There are more to add as coverage criteria and not only

full branch and class coverage

will be enough. If we're talking about Basic coverage criteria there are a number of coverage criteria, the main ones:

• Function coverage - Has each function (or subroutine) in the program been called?
• Statement coverage - Has each statement in the program been executed?
• Already mentioned Branch coverage - Has each branch (aka DD-path) of each control structure (such as in if and case statements) been executed? For example , given an if statement, have both the true and false branches been executed? Another way of saying this is, has every edge in the program been executed?
• Condition coverage (or predicate coverage) - Has each Boolean sub-expression evaluated both to true and false?

If you're interested and want to read more about - code coverage criteria .