There are several different tests that can be done to test for and detect cancer.
Sometimes you need more than one test to know for sure if you have cancer or not because some tests may test positive while it may turn out that you're not really sick with cancer at all.
So more than one test needs to be done for testing for cancer.
Some of those tests for cancer are needle biopsies, tumor biopsy, endoscopic examination, surgery, or genetic testing.
Blood tests are also a useful test for cancer as well as urine tests to test for bladder cancer and if it's colon cancer they will test by using a camera up your anus and other ways such as through your poop.