How long do you code without actually testing/checking the results/output?

And how well do you do? Does it work straight away?

I started refactoring my React widget today in the morning, didn't actually test the code until I was done rewriting the code at about 3 PM. After that, I had to fix some silly mistakes for about half an hour. After that, everything worked as expected :)

I was wondering if you do this too. Is it a bad practice?