Asserting against booleans makes error tracking more difficult.
TL;DR: Don't assert true unless you are checking a boolean
- Fail Fast Principle
-
Check if the boolean condition can be rewritten better
-
Favor assertEquals
When asserting to a boolean our test engines cannot help us very much.
They just tell us something failed.
Error tracking gets more difficult.
<?
final class RangeUnitTest extends TestCase {
function testValidOffset() {
$range = new Range(1, 1);
$offset = $range->offset();
$this->assertTrue(10 == $offset);
// No functional essential description :(
// Accidental description provided by tests is very bad
}
}
// When failing Unit framework will show us
//
// 1 Test, 1 failed
// Failing asserting true matches expected false :(
// () <-- no business description :(
//
// <Click to see difference> - Two booleans
// (and a diff comparator will show us two booleans)<?
final class RangeUnitTest extends TestCase {
function testValidOffset() {
$range = new Range(1, 1);
$offset = $range->offset();
$this->assertEquals(10, $offset, 'Pages must have 10 as offset');
// Expected value should always be first argument
// You add a functional essential description
// to complement accidental description provided by tests
}
}
// When failing Unit framework will show us
//
// 1 Test, 1 failed
// Failing asserting 0 matches expected 10
// All pages must have 10 as offset <-- business description
//
// <Click to see difference>
// (and a diff comparator will help us and it will be a great help
// for complex objects like objects or jsons)[X] Semi-Automatic
Some linters warn us if we are checking against boolean after setting this condition.
We need to change it to a more specific check.
- Test Smells
Try to rewrite your boolean assertions and you will fix the failures much faster.
Code Smell 101 - Comparison Against Booleans
Code Smell 07 - Boolean Variables
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I've finally learned what 'upward compatible' means. It means we get to keep all our old mistakes.
Dennie van Tassel
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This article is part of the CodeSmell Series.