Critical

Add the ReflectionClass fixture (already present — verify $this->reflection is set in setUp() before adding reflection-based tests):

private ReflectionClass $reflection;
protected function setUp(): void {
    $this->reflection = new ReflectionClass(Plugin::class);
}

Static property tests — assert exact values using self::assertSame():

public function testStaticPropertyName(): void {
    self::assertSame('Mail Services', Plugin::$name);
}

Verify the value in src/Plugin.php matches before asserting.

$settings array tests — assert key presence with assertArrayHasKey, exact values with assertSame, and cross-field invariants:

// Invariant: PREFIX matches TABLE
self::assertSame(Plugin::$settings['TABLE'], Plugin::$settings['PREFIX']);
// Invariant: TITLE_FIELD starts with PREFIX
self::assertStringStartsWith(Plugin::$settings['PREFIX'].'_', Plugin::$settings['TITLE_FIELD']);

Verify assertCount(17, Plugin::$settings) matches the actual key count in src/Plugin.php.

getHooks() tests — assert array shape and that every handler references Plugin::class with a real method:

$hooks = Plugin::getHooks();
self::assertArrayHasKey('mail.load_processing', $hooks);
self::assertSame(Plugin::class, $hooks['mail.load_processing'][0]);
// All hook keys must be prefixed with Plugin::$module.'.'
foreach (array_keys($hooks) as $key) {
    self::assertStringStartsWith(Plugin::$module.'.', $key);
}

Handler signature tests — use ReflectionClass, never call the method:

$method = $this->reflection->getMethod('loadProcessing');
self::assertCount(1, $method->getParameters());
self::assertSame(
    'Symfony\\Component\\EventDispatcher\\GenericEvent',
    $method->getParameters()[0]->getType()->getName()
);

Apply to loadProcessing, getDeactivate, getSettings.

Source-file string assertions — read the source once and assert tokens exist:

$source = file_get_contents((string) $this->reflection->getFileName());
self::assertStringContainsString('myadmin_log(', $source);
self::assertStringContainsString('get_module_db(', $source);
self::assertStringContainsString("self::$module.'.activate'", $source);

Verify by running composer test — all tests must pass with no warnings (failOnWarning="true" in config).