Does 100% code coverage mean that the code is correct?

Question

If you have 100% test coverage and all tests pass does that mean that the code is guaranteed to be correct and writing more tests is pointless?

Answer 1

It's only correct as far as the logic of your testing is correct.

I'll give the most stupid example possible...

If I for example have a class (Java):

public class Example {

    public int timesTwo(int x){
        return x*2;
    }

}

with the following test (which you can see it being illogical and useless)

public class ExampleTest {

    @Test
    public void timesTwo() {
        new Example().timesTwo(5);
        assertTrue(true);
    }
    
}

Most coverage tools will say that this class has been tested 100%! So no, coverage is a good indicator of what needs to be tested; but the test logic itself isn't assured.