Data providers can be a perfect fit to assert a lot of expectations without writing a full test for each.
This makes it cheap and easy to add more test cases. For an in-depth introduction to data providers, I recommend this excellent article on the Tighten blog.
class AddTest extends TestCase
{
/** @dataProvider values */
public function it_adds_values(int $a, int $b, int $result): void
{
$this->assertEquals($result, add($a, $b));
}
public function values(): array
{
return [
[1, 1, 2],
[1, 2, 3],
[5, 5, 10],
// …
];
}
}
Data providers run setUp for each value. If you need a clean slate for every test, there’s no way around this. If you don’t, data providers make your tests slower than they need to be.
Consider a heavier integration test that migrate & seeds the database in setUp().
class MyTest extends TestCase
{
public function setUp(): void
{
parent::setUp();
// Migrate and seed database values…
}
/** @dataProvider values */
public function it_does_something(string $value): void
{
// …
}
public function values(): array
{
return [ /* … */ ];
}
}
Each case in values() will re-seed the database. If this isn’t needed, you’re better off looping over the values yourself.
class MyTest extends TestCase
{
public function setUp(): void
{
parent::setUp();
// Do some heavy lifting…
}
public function it_does_something(): void
{
$values = [ /* … */ ];
foreach ($this->value() as $value) {
// …
}
}
public function values(): array
{
return [ /* … */ ];
}
}
We recently updated a few tests in a project we’re working on, and it almost doubled the speed!
With a data provider:
Time: 00:08.517, Memory: 92.50 MB
OK (43 tests, 43 assertions)
In a loop:
Time: 00:04.448, Memory: 70.14 MB
OK (1 test, 43 assertions)
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