Continue running test cases on failure.

Before this change an incorrect test case would break out of the loop, resulting
in only one failure being visible.

After the change the failure of many test cases can be displayed one after the
other, as displayed below:

--- FAIL: TestRead (0.00 seconds)
	bit_test.go:88: [170 85] with reads [3 3 3 3 3 1]: read 4 gave 2, expected 5
	bit_test.go:88: [170 85] with reads [3 3 3 3 3 1]: read 5 gave 1, expected 2
FAIL