If that's a good description, then gwern's example would fall under "gather[ing]".

The programmer is indeed gathering evidence, but I don't see how they are gathering evidence in a way that is meant to produce confirming rather than disconfirming evidence. As I have explained, the test could show a correct value for the troublesome variable and be evidence against the suspect line being the bug. The test will be somewhat biased towards confirmation in that it is really testing if the suspect line has a bug or any earlier line has a bug, but I don't think this bias reflects the programmer seeking only confirming evidence so much as not understanding what they are testing.

The bias the programmer is exhibiting in gwern's example is the same one that makes people fail the Wason selection task -- searching for confirming evidence rather than disconfirming evidence.

That is not the cause of failure in the Wason selection task. The problem is not using contrapositives, that is, realizing "even implies red" is logically equivalent to its contrapositive "not red implies not even", so to test "even implies red" you have to check cards that show an even number or a non red color.

This is similar to the failure to use contrapositives behind the Positive Test Bias, which is itself similar to gwern's example in that it involves failure to test every aspect of the hypothesis.