'''

*Procedure — test:write · PHP*

* Test class name = class under test + `Test` suffix (e.g. `MyClassTest`)
* Test class extends `\PHPUnit\Framework\TestCase` (or a subclass)
* One test class per production class; mirror the source tree under `tests/`
* Test methods start with `test` (e.g. `testParsesEmptyString`)
* Use `DataProvider` attribute (PHP 8.1+) for parameterised test cases:

[source,php]
----
#[DataProvider( 'provideParseData' )]
public function testParse( string $input, string $expected ): void {
    $this->assertSame( $expected, ( new MyParser() )->parse( $input ) );
}

public static function provideParseData(): array {
    return [
        'empty string' => [ '', '' ],
        'simple value' => [ 'foo', 'FOO' ],
    ];
}
----

* Assertions: prefer specific assertions (`assertSame`, `assertCount`, `assertInstanceOf`) over `assertTrue`
* One logical assertion per test; multiple +assert*+ calls are fine when they verify the same concern
* Test names describe behavior, not implementation: `testReturnsNullForMissingKey`, not `testMethod1`