diff --git a/f5c95406e1cf6fe15e67f77eba8593013a789ada b/d8b0941aa9db8a5d10a69c77989eff84e247ffff
index f5c9540..d8b0941 100644
--- a/f5c95406e1cf6fe15e67f77eba8593013a789ada
+++ b/d8b0941aa9db8a5d10a69c77989eff84e247ffff
@@ -11,7 +11,7 @@
 	"require": {
 		"php": ">=8.1",
 		"monolog/monolog": "^2.0",
-		"psr/container": "2.0.2"
+		"psr/container": "^2.0.2"
 	},
 	"require-dev": {
 		"holonet/hdev": "~1.1.0@dev",
@@ -19,7 +19,7 @@
 		"spatie/phpunit-snapshot-assertions": "dev-main"
 	},
 	"provide": {
-		"psr/container-implementation": "2.0.2"
+		"psr/container-implementation": "^2.0.2"
 	},
 	"repositories": [
 		{
@@ -60,7 +60,7 @@
 		"test": [
 			"@composer validate",
 			"@composer normalize --dry-run --diff",
-			"@php -d memory_limit=-1 vendor/phpunit/phpunit/phpunit -c phpunit.xml",
+			"@php -d xdebug.mode=coverage -d memory_limit=-1 vendor/phpunit/phpunit/phpunit -c phpunit.xml",
 			"@php -d memory_limit=-1 vendor/friendsofphp/php-cs-fixer/php-cs-fixer fix --verbose --dry-run --ansi",
 			"@php -d memory_limit=-1 vendor/vimeo/psalm/psalm"
 		]

diff --git a/1143f81053f5f8ef420d7160d252fae32606b2b4 b/666402878461d1424cc03cc31a398400131fb5b7
index 1143f81..6664028 100644
--- a/1143f81053f5f8ef420d7160d252fae32606b2b4
+++ b/666402878461d1424cc03cc31a398400131fb5b7
@@ -50,16 +50,16 @@ class Collection implements Countable, IteratorAggregate {
 	}

 	/**
-	 * return a reference so we can change e.g. sub arrays from this call
+	 * return a reference, so we can change e.g. sub arrays from this call
 	 *  => cannot use our own get() method.
 	 */
-	public function __get(string $key): mixed {
-		if (is_object($this->data[$key]) || $this->data[$key] === null) {
-			//only actual variables should be returned by reference
-			return $this->data[$key];
+	public function &__get(string $key): mixed {
+		if (!$this->has($key)) {
+			$null = null;
+			return $null;
 		}

-		return $this->data[$key] ?? null;
+		return $this->data[$key];
 	}

 	public function clear(): void {

diff --git a/21ee65a51cd70364e05a7f2ea12430f60941afeb b/d6bc6a57128a2919c477cdb80941c7864713ed1d
index 21ee65a..d6bc6a5 100644
--- a/21ee65a51cd70364e05a7f2ea12430f60941afeb
+++ b/d6bc6a57128a2919c477cdb80941c7864713ed1d
@@ -75,7 +75,6 @@ class Container implements ContainerInterface {
 	 * @template T
 	 * @param class-string<T> $class
 	 * @return T
-	 * @psalm-suppress InvalidReturnType
 	 * @psalm-suppress InvalidReturnStatement
 	 */
 	public function byType(string $class, ?string $alias = null): object {

diff --git a/673104a5d862e8b99bf9ee18c0beba4698e5d1cc b/693d31a10cd04f72185098dd3bee63e444aa2e26
index 673104a..693d31a 100644
--- a/673104a5d862e8b99bf9ee18c0beba4698e5d1cc
+++ b/693d31a10cd04f72185098dd3bee63e444aa2e26
@@ -47,7 +47,6 @@ class ErrorDispatcher {
 	public function __construct() {
 		/**
 		 * @psalm-suppress InvalidArgument
-		 * @psalm-suppress MissingClosureParamType
 		 */
 		set_error_handler(function (...$args): void {
 			foreach ($this->errorHandlers as $handler) {
@@ -55,10 +54,6 @@ class ErrorDispatcher {
 			}
 		});

-		/**
-		 * @psalm-suppress InvalidArgument
-		 * @psalm-suppress MissingClosureParamType
-		 */
 		set_exception_handler(function (...$args): void {
 			foreach ($this->exceptionHandlers as $handler) {
 				$handler(...$args);
@@ -66,7 +61,6 @@ class ErrorDispatcher {
 		});

 		/**
-		 * @psalm-suppress InvalidArgument
 		 * @psalm-suppress MissingClosureParamType
 		 */
 		register_shutdown_function(function (...$args): void {

<?php
/**
 * This file is part of the hdev common library package
 * (c) Matthias Lantsch.
 *
 * @license http://www.wtfpl.net/ Do what the fuck you want Public License
 * @author  Matthias Lantsch <[email protected]>
 */

namespace holonet\common\tests;

use holonet\common\collection\Collection;
use PHPUnit\Framework\TestCase;
use PHPUnit\Framework\Attributes\CoversClass;

#[CoversClass(Collection::class)]
class CollectionTest extends TestCase {
	public function test_constructor_with_initial_data(): void {
		$initialData = ['foo' => 'bar', 'baz' => 123];
		$collection = new Collection($initialData);

		$this->assertSame($initialData, $collection->all());
	}

	public function test_constructor_with_empty_initial_data(): void {
		$collection = new Collection();

		$this->assertTrue($collection->empty());
	}

	public function test_set_and_get(): void {
		$collection = new Collection();
		$collection->set('key1', 'value1');
		$collection->key2 = 'value2';

		$this->assertEquals('value1', $collection->key1);
		$this->assertEquals('value2', $collection->get('key2'));
		$this->assertNull($collection->NonsensicalKey);
	}

	public function test_set_with_null_key(): void {
		$collection = new Collection();
		$collection->set(null, 'value');

		$this->assertEquals('value', $collection->get(0)); // 0 is the index when the key is null
	}

	public function test_set_with_null_key_adds_to_the_end(): void {
		$collection = new Collection(['existingValue']);
		$collection->set(null, 'newValue');

		$this->assertEquals(['existingValue', 'newValue'], $collection->all());
	}

	public function test_get_with_default(): void {
		$collection = new Collection(['existingKey' => 'value']);

		$this->assertEquals('value', $collection->get('existingKey'));
		$this->assertEquals('default', $collection->get('nonExistingKey', 'default'));
	}

	public function test_changes_to_magic_method_reads_work(): void {
		$collection = new Collection(['null' => null, 'object' => new \stdClass(), 'array' => ['key' => 'value']]);

		// make sure the reference to null points nowhere
		$reference = $collection->null;
		$reference = 'test';
		$this->assertNull($collection->get('null'));

		// make sure the reference to the object works as expected
		$reference = $collection->object;
		$reference->test = 'test';
		$this->assertEquals('test', $collection->get('object')->test);
		$collection->object->test = 'new value';
		$this->assertEquals('new value', $collection->get('object')->test);

		// make sure the reference to the array works as expected
		$collection->array['key'] = 'new value';
		$this->assertEquals(array('key' => 'new value'), $collection->get('array'));
		$collection->array[] = 'appended';
		$this->assertEquals(array('key' => 'new value', 'appended'), $collection->get('array'));

		// changes to a subarray
		$collection = new Collection(['key' => ['subkey' => 'value']]);
		$collection->key['subkey'] = 'new value';

		$this->assertEquals(['key' => ['subkey' => 'new value']], $collection->all());
	}

	public function test_has(): void {
		$collection = new Collection(['existingKey' => 'value']);

		$this->assertTrue($collection->has('existingKey'));
		$this->assertTrue(isset($collection->existingKey));
		$this->assertFalse($collection->has('nonExistingKey'));
		$this->assertFalse(isset($collection->nonExistingKey));

		$collection->set('nullKey', null);

		// behave differently when the value is null
		// => the key is set but the offset definitely is not "isset"
		$this->assertTrue($collection->has('nullKey'));
		$this->assertFalse(isset($collection->nullKey));
	}

	public function test_remove(): void {
		$collection = new Collection(['key1' => 'value1', 'key2' => 'value2']);
		$collection->remove('key1');

		$this->assertEquals(['key2' => 'value2'], $collection->all());

		unset($collection->key2);

		$this->assertEquals([], $collection->all());
	}

	public function test_clear(): void {
		$collection = new Collection(['key' => 'value']);
		$collection->clear();

		$this->assertTrue($collection->empty());
	}

	public function test_count(): void {
		$collection = new Collection(['key1' => 'value1', 'key2' => 'value2']);

		$this->assertEquals(2, $collection->count());
	}

	public function test_empty(): void {
		$collection = new Collection();

		$this->assertTrue($collection->empty());

		$collection->set('key', 'value');

		$this->assertFalse($collection->empty());
	}

	public function test_iterator(): void {
		$collection = new Collection(['key1' => 'value1', 'key2' => 'value2']);
		$iterator = $collection->getIterator();

		$this->assertEquals(['key1' => 'value1', 'key2' => 'value2'], iterator_to_array($iterator));
	}

	public function test_merge(): void {
		$collection = new Collection(['key1' => 'value1', 'key2' => 'value2']);
		$collection->merge(['key2' => 'newValue2', 'key3' => 'value3']);

		$this->assertEquals(['key1' => 'value1', 'key2' => 'newValue2', 'key3' => 'value3'], $collection->all());
	}

	public function test_replace(): void {
		$collection = new Collection(['key1' => 'value1', 'key2' => 'value2']);
		$collection->replace(['key3' => 'value3']);

		$this->assertEquals(['key3' => 'value3'], $collection->all());
	}

	public function test_all(): void {
		$collection = new Collection(['key' => 'value']);

		$this->assertEquals(['key' => 'value'], $collection->all());
	}

	public function test_filter_param_can_be_used_to_filter_keys(): void {
		$collection = new Collection(['key1' => 'value1', 'key2' => 'value2', 'key3' => 'value3']);

		$this->assertEquals(['key1' => 'value1', 'key3' => 'value3'], $collection->all(['key1', 'key3']));
	}

}

diff --git a/c8f6b5cb9102a780e073d81b93c3d49b423508bc b/7af8d219d10448638ea998ec46f742b23c21be41
index c8f6b5c..7af8d21 100644
--- a/c8f6b5cb9102a780e073d81b93c3d49b423508bc
+++ b/7af8d219d10448638ea998ec46f742b23c21be41
@@ -33,7 +33,7 @@ class ConfigRegistryTest extends TestCase {
 		putenv('ENV_VALUE_2=');
 	}

-	public function testEnvPlaceholderReplacement(): void {
+	public function test_env_placeholder_gets_replaced(): void {
 		$registry = new ConfigRegistry();
 		$registry->setAll(array(
 			'test' => '%env(ENV_VALUE)%',
@@ -44,7 +44,7 @@ class ConfigRegistryTest extends TestCase {
 		$this->assertSame('test value', $registry->get('test2'));
 	}

-	public function testNormalPlaceholdersStillWork(): void {
+	public function test_normal_placeholders_still_work(): void {
 		$registry = new ConfigRegistry();
 		$registry->setAll(array(
 			'test' => '%test_prop%',
@@ -54,7 +54,7 @@ class ConfigRegistryTest extends TestCase {
 		$this->assertSame('cool', $registry->get('test'));
 	}

-	public function testVerifiedDto(): void {
+	public function test_config_data_can_be_fetched_as_a_verified_dto_object(): void {
 		$this->expectException(BadEnvironmentException::class);
 		$this->expectExceptionMessage('Faulty config with key \'test.testProp\': testProp must be exactly 11 characters long');

@@ -72,7 +72,7 @@ class ConfigRegistryTest extends TestCase {
 		$registry->verifiedDto('test', $dto);
 	}

-	public function testVerifiedDtoTypeError(): void {
+	public function test_faulty_config_data_fetch_with_dto_object_throws_type_error(): void {
 		$this->expectException(BadEnvironmentException::class);
 		$this->expectExceptionMessage('Faulty config with key \'test\': TypeError: Cannot assign array to property class@anonymous::$testProp of type string');

@@ -90,16 +90,34 @@ class ConfigRegistryTest extends TestCase {
 		$registry->verifiedDto('test', $dto);
 	}

-	public function testVerifiedDtoUsingClass(): void {
+	public function test_config_data_can_be_fetched_using_an_actual_dto_object_class(): void {
 		$registry = new ConfigRegistry();
 		$registry->set('test', 'amazing value');

-		$dto = $registry->verifiedDto('test', TestDto::class);
+		$dto = $registry->verifiedDto('test', holonet_common_tests_ConfigRegistryTest_TestDto::class);
 		$this->assertSame('amazing value', $dto->value);
 	}
+
+	public function test_accessing_a_non_existing_key_will_throw_a_helpful_exception(): void {
+		$this->expectException(BadEnvironmentException::class);
+		$this->expectExceptionMessage('Faulty config with key \'test\': Config item doesn\'t exist');
+
+		$registry = new ConfigRegistry();
+		$registry->asDto('test', holonet_common_tests_ConfigRegistryTest_TestDto::class);
+	}
+
+	public function test_having_an_unset_environment_placeholder_in_a_value_defaults_to_empty_string(): void {
+		$registry = new ConfigRegistry();
+		$registry->setAll(array(
+			'test' => '%env(ENV_VALUE_3)%',
+		));
+
+		$this->assertSame('', $registry->get('test'));
+	}
+
 }

-class TestDto {
+class holonet_common_tests_ConfigRegistryTest_TestDto {
 	public function __construct(
 		#[MinLength(4)]
 		public string $value