Tests that assert nothing, or assert a constant

Tests and verification: one of the ways AI coding agents bloat software, from lessloc's pattern catalog. lessloc catches it as empty-test.

What makes tests that assert nothing, or assert a constant a bad practice?

The standard that calls it a bad practice: Carr, TDD anti-patterns: The Liar.

lessloc catches it as empty-test.

empty-test (tier 1): A test that asserts nothing or only a constant, or one that mocks the code it tests.

Caught as empty-test:

python

def test_total():
    total([1, 2])


def test_sum():
    assert True

Written well:

python

def test_total():
    assert total([1, 2]) == 3


def test_import_runs():
    import json

Caught as empty-test:

python

def test_render():
    expected = """\
[a]
b = 1
"""
    render(expected)

Written well:

python

def test_render():
    expected = """\
[a]
b = 1
"""
    assert render() == expected

Caught as empty-test:

import { test } from "node:test";
test("adds", () => {
  add(1, 2);
});

Written well:

import { test } from "node:test";
import assert from "node:assert";
test("adds", () => {
  assert.equal(add(1, 2), 3);
});

The other patterns in Tests and verification:

Behavior added with no test changed in the same change: lessloc gives every session the rule: new behavior gets one focused test.
Deleted, skipped or force-passed tests: lessloc catches it as weakened-tests.
Test-only branches in production code: lessloc catches it as test-logic.
Tests that mock the code they test: lessloc catches it as empty-test.
Production code that branches on a value from the tests: lessloc catches it as test-logic.
Stopping short: a requested function never written: lessloc catches it as unaddressed: names a request asks to exist ("add a --status flag", "implement export_csv()") are looked for in the final repository; one that appears nowhere holds the turn.
Stopping short: part of the problem left failing: lessloc catches it as unfinished: in a turn that changed code, the agent's last reply is read sentence by sentence, with headings and lead-ins speaking for what is under them.
Saying "done" without a passing run on the final state: lessloc catches it as tests-failed and unverified: the agent's own test runs, as its host reported them, are the evidence for the exact tree; a run that fails on the final state, or a change to how the tests run, holds the turn once, and a final state no run verified is written to the record; lessloc test, verify and ci record evidence too.
A refactor that changes existing tests: lessloc catches it as refactor-tests.