Duplicate test nodeids in command line arguments show incorrect collection count but execute only once

[steadyfirmness]

Description:

When passing duplicate test nodeids in the command line arguments, pytest shows an incorrect collection count but only executes the test once.

Steps to Reproduce:

Run pytest with duplicate test nodeids:

pytest tests/test_foo.py::test_pass tests/test_foo.py::test_pass

Observed Behavior:

collected 2 items

tests/test_foo.py::test_pass PASSED                                      [100%]

============================== 1 passed in 0.01s ===============================

The output shows "collected 2 items" but only executes and reports 1 test

The progress percentage shows [100%] after one test

Expected Behavior:

Either:

Pytest should deduplicate the nodeids during collection and show "collected 1 item", or

Pytest should execute the test twice (if intentional duplicate execution is desired)

Environment:

pytest version: 8.3.5

Python version: 3.12

OS: macos

Additional Information:

This might cause confusion when:

Accidentally passing duplicate tests in complex command line invocations

Using tools that generate pytest command lines automatically

Trying to understand test counts in CI output