Coverage

• Statement Coverage (aka Line Coverage)
  • Covers all lines
• Branch Coverage
  • Covers all branches (both if-else statements)
• Path Coverage
  • Covers all paths
• Mutation Coverage
• Tools:
  • jacoco
  • pitest

Statement Coverage vs Branch Coverage

• https://stackoverflow.com/questions/14519416/a-difference-between-statement-and-decision-coverage
• https://stackoverflow.com/questions/8229236/differences-between-line-and-branch-coverage
• 100% Branch Coverage $⟹$ 100% Statement Coverage

public int getNameLength(boolean isCoolUser) {
    User user = null;
    if (isCoolUser) {
        user = new John();
    }
    return user.getName().length(); // NPE if user == null
}

• To Cover all statements: (1 Test case)
  • isCoolUser = true
• To Cover all branches: (2 Test cases)
  • isCoolUser = true
  • isCoolUser = false
• It is necessary as you can see that if you don’t cover all the branches then you will get NPE

Simpler example

int fun(int a, int b) {
    if (a > 0) {
        if (b > 0) {
            return 1;
        }
    } else {
        return 2;
    }
}

• To cover all statements (2 Test cases)
  • a = 10, b = 10
  • a = -1, b = anything
• To cover all branches (3 Test cases)
  • a = 10, b = 10
  • a = 10, b = -1
  • a = -1, b = anything