trivial-inputs

A test passes the code it tests only default values.

Group: Tests
Runs: On by default
Level: warning
Reads: Tests
Fix: None: which values the test should pass is the author's choice
Defends: Fidelity: when the code is broken, the test fails.

Why

Every constant the test passes to the code it tests is its type's zero value: zero, false, an empty string or collection, or a missing value. Code that ignores its input entirely passes such a test. A test that also passes a value it computed is not reported.

The fix, as Ur suggests it: pass values other than the defaults.

For agents

Pass the code under test values other than its types' defaults, such as 7 or "apple" rather than 0 or "", so a test fails when the code ignores its input.

Example

shop/pricing.py

def apply_discount(price, percent):
    return price - price * percent / 100

tests/test_pricing.py

from shop.pricing import apply_discount


def test_applies_discount():
    assert apply_discount(0, 0) == 0

What Ur prints

$ ur lint --rule trivial-inputs
warning[trivial-inputs]: every value test `test_applies_discount` passes to the code it tests is a default, so ignoring its input passes too
  --> ./tests/test_pricing.py:5:12 test `test_applies_discount`
  = step 1: ./tests/test_pricing.py:5:27 a default value
  = step 2: ./tests/test_pricing.py:5:30 a default value
  = hint: pass values other than the defaults
  = see: Choosing Values for Robust Tests, Google Testing Blog (2026-06-04), https://testing.googleblog.com/2026/06/choosing-values-for-robust-tests.html
0 clone classes and 1 test finding in 2 files

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Source

Choosing Values for Robust Tests, Google Testing Blog (2026-06-04).