Coverage for branches : 92%

# Demonstrate some issues with coverage.py branch testing. 

def my_function(x): 

    """This isn't real code, just snippets...""" 

    # An infinite loop is structurally still a branch: it can next execute the 

    # first line of the loop, or the first line after the loop.  But 

    # "while True" will never jump to the line after the loop, so the line 

    # is shown as a partial branch: 

    i = 0 

17    while True: 

        print "In while True" 

        if i > 0: 

            break 

        i += 1 

    print "Left the True loop" 

    # Notice that "while 1" also has this problem.  Even though the compiler 

    # knows there's no computation at the top of the loop, it's still expressed 

    # in byte code as a branch with two possibilities. 

    i = 0 

29    while 1: 

        print "In while 1" 

        if i > 0: 

            break 

        i += 1 

    print "Left the 1 loop" 

    # Coverage.py lets the developer exclude lines that he knows will not be 

    # executed.  So far, the branch coverage doesn't use all that information 

    # when deciding which lines are partially executed. 

    # 

    # Here, even though the else line is explicitly marked as never executed, 

    # the if line complains that it never branched to the else: 

42    if x < 1000: 

        # This branch is always taken 

        print "x is reasonable" 

    else:   # pragma: nocover 

        print "this never happens" 

    # try-except structures are complex branches.  An except clause with a 

    # type is a three-way branch: there could be no exception, there could be 

    # a matching exception, and there could be a non-matching exception. 

    # 

    # Here we run the code twice: once with no exception, and once with a 

    # matching exception.  The "except" line is marked as partial because we 

    # never executed its third case: a non-matching exception. 

    for y in (1, 2): 

        try: 

            if y % 2: 

                raise ValueError("y is odd!") 

58 59        except ValueError: 

            print "y must have been odd" 

        print "done with y" 

    print "done with 1, 2" 

    # Another except clause, but this time all three cases are executed.  No 

    # partial lines are shown: 

    for y in (0, 1, 2): 

        try: 

            if y % 2: 

                raise ValueError("y is odd!") 

            if y == 0: 

                raise Exception("zero!") 

        except ValueError: 

            print "y must have been odd" 

        except: 

            print "y is something else" 

        print "done with y" 

    print "done with 0, 1, 2" 

my_function(1)