diff --git a/benchmarks/BenchAsset/AbstractFactoryFoo.php b/benchmarks/BenchAsset/AbstractFactoryFoo.php
index 4d61801f..ddbe7d75 100644
--- a/benchmarks/BenchAsset/AbstractFactoryFoo.php
+++ b/benchmarks/BenchAsset/AbstractFactoryFoo.php
@@ -12,7 +12,7 @@
 
 class AbstractFactoryFoo implements AbstractFactoryInterface
 {
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         if ($requestedName === 'foo') {
             return new Foo($options);
@@ -20,7 +20,7 @@ public function __invoke(ContainerInterface $container, $requestedName, array $o
         return false;
     }
 
-    public function canCreate(ContainerInterface $container, $requestedName)
+    public function canCreate(ContainerInterface $container, string $requestedName) : bool
     {
         return ($requestedName === 'foo');
     }
diff --git a/benchmarks/BenchAsset/FactoryFoo.php b/benchmarks/BenchAsset/FactoryFoo.php
index 474ea283..8fa9b3c3 100644
--- a/benchmarks/BenchAsset/FactoryFoo.php
+++ b/benchmarks/BenchAsset/FactoryFoo.php
@@ -12,7 +12,7 @@
 
 class FactoryFoo implements FactoryInterface
 {
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         return new Foo($options);
     }
diff --git a/src/AbstractFactory/ConfigAbstractFactory.php b/src/AbstractFactory/ConfigAbstractFactory.php
index eef3c935..a2a7dc29 100644
--- a/src/AbstractFactory/ConfigAbstractFactory.php
+++ b/src/AbstractFactory/ConfigAbstractFactory.php
@@ -8,6 +8,7 @@
 namespace Zend\ServiceManager\AbstractFactory;
 
 use ArrayObject;
+use Psr\Container\ContainerInterface;
 use Zend\ServiceManager\Exception\ServiceNotCreatedException;
 use Zend\ServiceManager\Factory\AbstractFactoryInterface;
 
@@ -24,7 +25,7 @@ final class ConfigAbstractFactory implements AbstractFactoryInterface
      *
      * {@inheritdoc}
      */
-    public function canCreate(\Psr\Container\ContainerInterface $container, $requestedName)
+    public function canCreate(ContainerInterface $container, string $requestedName) : bool
     {
         if (! $container->has('config') || ! array_key_exists(self::class, $container->get('config'))) {
             return false;
@@ -38,7 +39,7 @@ public function canCreate(\Psr\Container\ContainerInterface $container, $request
     /**
      * {@inheritDoc}
      */
-    public function __invoke(\Psr\Container\ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         if (! $container->has('config')) {
             throw new ServiceNotCreatedException('Cannot find a config array in the container');
diff --git a/src/AbstractFactory/ReflectionBasedAbstractFactory.php b/src/AbstractFactory/ReflectionBasedAbstractFactory.php
index 6df35677..6fb64b08 100644
--- a/src/AbstractFactory/ReflectionBasedAbstractFactory.php
+++ b/src/AbstractFactory/ReflectionBasedAbstractFactory.php
@@ -110,7 +110,7 @@ public function __construct(array $aliases = [])
      *
      * @return DispatchableInterface
      */
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         $reflectionClass = new ReflectionClass($requestedName);
 
@@ -136,7 +136,7 @@ public function __invoke(ContainerInterface $container, $requestedName, array $o
     /**
      * {@inheritDoc}
      */
-    public function canCreate(ContainerInterface $container, $requestedName)
+    public function canCreate(ContainerInterface $container, string $requestedName) : bool
     {
         return class_exists($requestedName);
     }
@@ -146,13 +146,11 @@ public function canCreate(ContainerInterface $container, $requestedName)
      *
      * Returns a callback for resolving a parameter to a value, but without
      * allowing mapping array `$config` arguments to the `config` service.
-     *
-     * @param ContainerInterface $container
-     * @param string $requestedName
-     * @return callable
      */
-    private function resolveParameterWithoutConfigService(ContainerInterface $container, $requestedName)
-    {
+    private function resolveParameterWithoutConfigService(
+        ContainerInterface $container,
+        string $requestedName
+    ) : callable {
         /**
          * @param ReflectionParameter $parameter
          * @return mixed
@@ -169,12 +167,8 @@ private function resolveParameterWithoutConfigService(ContainerInterface $contai
      *
      * Unlike resolveParameter(), this version will detect `$config` array
      * arguments and have them return the 'config' service.
-     *
-     * @param ContainerInterface $container
-     * @param string $requestedName
-     * @return callable
      */
-    private function resolveParameterWithConfigService(ContainerInterface $container, $requestedName)
+    private function resolveParameterWithConfigService(ContainerInterface $container, string $requestedName) : callable
     {
         /**
          * @param ReflectionParameter $parameter
@@ -193,15 +187,15 @@ private function resolveParameterWithConfigService(ContainerInterface $container
     /**
      * Logic common to all parameter resolution.
      *
-     * @param ReflectionParameter $parameter
-     * @param ContainerInterface $container
-     * @param string $requestedName
      * @return mixed
      * @throws ServiceNotFoundException If type-hinted parameter cannot be
      *   resolved to a service in the container.
      */
-    private function resolveParameter(ReflectionParameter $parameter, ContainerInterface $container, $requestedName)
-    {
+    private function resolveParameter(
+        ReflectionParameter $parameter,
+        ContainerInterface $container,
+        string $requestedName
+    ) {
         if ($parameter->isArray()) {
             return [];
         }
diff --git a/src/AbstractPluginManager.php b/src/AbstractPluginManager.php
index ca196472..e62c0d05 100644
--- a/src/AbstractPluginManager.php
+++ b/src/AbstractPluginManager.php
@@ -107,7 +107,7 @@ public function __construct($configInstanceOrParentLocator = null, array $config
      * {@inheritDoc}
      * @throws InvalidServiceException
      */
-    public function configure(array $config)
+    public function configure(array $config) : ServiceManager
     {
         if (isset($config['services'])) {
             foreach ($config['services'] as $service) {
@@ -125,7 +125,7 @@ public function configure(array $config)
      *
      * {@inheritDoc}
      */
-    public function setService($name, $service)
+    public function setService(string $name, $service) : void
     {
         $this->validate($service);
         parent::setService($name, $service);
@@ -165,7 +165,7 @@ public function get($name, array $options = null)
     /**
      * {@inheritDoc}
      */
-    public function validate($instance)
+    public function validate($instance) : void
     {
         if (method_exists($this, 'validatePlugin')) {
             trigger_error(sprintf(
diff --git a/src/Config.php b/src/Config.php
index b82d4c85..ca51ebdf 100644
--- a/src/Config.php
+++ b/src/Config.php
@@ -79,7 +79,7 @@ public function __construct(array $config = [])
     /**
      * @inheritdoc
      */
-    public function configureServiceManager(ServiceManager $serviceManager)
+    public function configureServiceManager(ServiceManager $serviceManager) : ServiceManager
     {
         return $serviceManager->configure($this->config);
     }
@@ -87,7 +87,7 @@ public function configureServiceManager(ServiceManager $serviceManager)
     /**
      * @inheritdoc
      */
-    public function toArray()
+    public function toArray() : array
     {
         return $this->config;
     }
@@ -98,7 +98,7 @@ public function toArray()
      *
      * @link https://github.com/zendframework/zend-servicemanager/pull/68
      */
-    private function merge(array $a, array $b)
+    private function merge(array $a, array $b) : array
     {
         foreach ($b as $key => $value) {
             if ($value instanceof MergeReplaceKeyInterface) {
diff --git a/src/ConfigInterface.php b/src/ConfigInterface.php
index 67e1aee6..7b9984bd 100644
--- a/src/ConfigInterface.php
+++ b/src/ConfigInterface.php
@@ -19,7 +19,7 @@ interface ConfigInterface
      * @param ServiceManager $serviceManager
      * @return ServiceManager
      */
-    public function configureServiceManager(ServiceManager $serviceManager);
+    public function configureServiceManager(ServiceManager $serviceManager) : ServiceManager;
 
     /**
      * Return configuration for a service manager instance as an array.
@@ -42,5 +42,5 @@ public function configureServiceManager(ServiceManager $serviceManager);
      *
      * @return array
      */
-    public function toArray();
+    public function toArray() : array;
 }
diff --git a/src/Exception/ContainerModificationsNotAllowedException.php b/src/Exception/ContainerModificationsNotAllowedException.php
index 8f315d66..4c2f16f4 100644
--- a/src/Exception/ContainerModificationsNotAllowedException.php
+++ b/src/Exception/ContainerModificationsNotAllowedException.php
@@ -18,9 +18,8 @@ class ContainerModificationsNotAllowedException extends DomainException implemen
 {
     /**
      * @param string $service Name of service that already exists.
-     * @return self
      */
-    public static function fromExistingService($service)
+    public static function fromExistingService(string $service) : self
     {
         return new self(sprintf(
             'The container does not allow replacing or updating a service'
diff --git a/src/Exception/CyclicAliasException.php b/src/Exception/CyclicAliasException.php
index b6b95c2d..7556dbaa 100644
--- a/src/Exception/CyclicAliasException.php
+++ b/src/Exception/CyclicAliasException.php
@@ -24,7 +24,7 @@ class CyclicAliasException extends InvalidArgumentException
      * @param string[] $aliases map of referenced services, indexed by alias name (string)
      * @return self
      */
-    public static function fromCyclicAlias($alias, array $aliases)
+    public static function fromCyclicAlias(string $alias, array $aliases) : self
     {
         $cycle = $alias;
         $cursor = $alias;
@@ -44,7 +44,7 @@ public static function fromCyclicAlias($alias, array $aliases)
      * @param string[] $aliases map of referenced services, indexed by alias name (string)
      * @return self
      */
-    public static function fromAliasesMap(array $aliases)
+    public static function fromAliasesMap(array $aliases) : self
     {
         $detectedCycles = array_filter(array_map(
             function ($alias) use ($aliases) {
@@ -72,10 +72,8 @@ function ($alias) use ($aliases) {
      * Retrieves the cycle detected for the given $alias, or `null` if no cycle was detected
      *
      * @param string[] $aliases
-     * @param string   $alias
-     * @return array|null
      */
-    private static function getCycleFor(array $aliases, $alias)
+    private static function getCycleFor(array $aliases, string $alias) : ?array
     {
         $cycleCandidate = [];
         $targetName     = $alias;
@@ -94,9 +92,8 @@ private static function getCycleFor(array $aliases, $alias)
 
     /**
      * @param string[] $aliases
-     * @return string
      */
-    private static function printReferencesMap(array $aliases)
+    private static function printReferencesMap(array $aliases) : string
     {
         $map = [];
 
@@ -109,18 +106,16 @@ private static function printReferencesMap(array $aliases)
 
     /**
      * @param string[][] $detectedCycles
-     * @return string
      */
-    private static function printCycles(array $detectedCycles)
+    private static function printCycles(array $detectedCycles) : string
     {
         return "[\n" . implode("\n", array_map([__CLASS__, 'printCycle'], $detectedCycles)) . "\n]";
     }
 
     /**
      * @param string[] $detectedCycle
-     * @return string
      */
-    private static function printCycle(array $detectedCycle)
+    private static function printCycle(array $detectedCycle) : string
     {
         $fullCycle   = array_keys($detectedCycle);
         $fullCycle[] = reset($fullCycle);
@@ -140,7 +135,7 @@ function ($cycle) {
      * @param bool[][] $detectedCycles
      * @return bool[][] de-duplicated
      */
-    private static function deDuplicateDetectedCycles(array $detectedCycles)
+    private static function deDuplicateDetectedCycles(array $detectedCycles) : array
     {
         $detectedCyclesByHash = [];
 
diff --git a/src/Exception/InvalidArgumentException.php b/src/Exception/InvalidArgumentException.php
index 4eb9e891..2a10d4f5 100644
--- a/src/Exception/InvalidArgumentException.php
+++ b/src/Exception/InvalidArgumentException.php
@@ -25,7 +25,7 @@ class InvalidArgumentException extends SplInvalidArgumentException implements Ex
      * @param mixed $initializer
      * @return self
      */
-    public static function fromInvalidInitializer($initializer)
+    public static function fromInvalidInitializer($initializer) : self
     {
         return new self(sprintf(
             'An invalid initializer was registered. Expected a callable or an'
@@ -39,7 +39,7 @@ public static function fromInvalidInitializer($initializer)
      * @param mixed $abstractFactory
      * @return self
      */
-    public static function fromInvalidAbstractFactory($abstractFactory)
+    public static function fromInvalidAbstractFactory($abstractFactory) : self
     {
         return new self(sprintf(
             'An invalid abstract factory was registered. Expected an instance of or a valid'
diff --git a/src/Factory/AbstractFactoryInterface.php b/src/Factory/AbstractFactoryInterface.php
index 03a0e471..13bb7aef 100644
--- a/src/Factory/AbstractFactoryInterface.php
+++ b/src/Factory/AbstractFactoryInterface.php
@@ -28,5 +28,5 @@ interface AbstractFactoryInterface extends FactoryInterface
      * @param  string $requestedName
      * @return bool
      */
-    public function canCreate(ContainerInterface $container, $requestedName);
+    public function canCreate(ContainerInterface $container, string $requestedName) : bool;
 }
diff --git a/src/Factory/DelegatorFactoryInterface.php b/src/Factory/DelegatorFactoryInterface.php
index 02e69c21..5ca34060 100644
--- a/src/Factory/DelegatorFactoryInterface.php
+++ b/src/Factory/DelegatorFactoryInterface.php
@@ -34,5 +34,5 @@ interface DelegatorFactoryInterface
      *     creating a service.
      * @throws ContainerException if any other error occurs
      */
-    public function __invoke(ContainerInterface $container, $name, callable $callback, array $options = null);
+    public function __invoke(ContainerInterface $container, string $name, callable $callback, array $options = null);
 }
diff --git a/src/Factory/FactoryInterface.php b/src/Factory/FactoryInterface.php
index 33084447..98936bc6 100644
--- a/src/Factory/FactoryInterface.php
+++ b/src/Factory/FactoryInterface.php
@@ -33,5 +33,5 @@ interface FactoryInterface
      *     creating a service.
      * @throws ContainerException if any other error occurs
      */
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null);
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null);
 }
diff --git a/src/Factory/InvokableFactory.php b/src/Factory/InvokableFactory.php
index 85ac0b58..7d8ca14d 100644
--- a/src/Factory/InvokableFactory.php
+++ b/src/Factory/InvokableFactory.php
@@ -25,7 +25,7 @@ final class InvokableFactory implements FactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         return (null === $options) ? new $requestedName : new $requestedName($options);
     }
diff --git a/src/Initializer/InitializerInterface.php b/src/Initializer/InitializerInterface.php
index 24c059c4..16ba4bcd 100644
--- a/src/Initializer/InitializerInterface.php
+++ b/src/Initializer/InitializerInterface.php
@@ -24,5 +24,5 @@ interface InitializerInterface
      * @param  object             $instance
      * @return void
      */
-    public function __invoke(ContainerInterface $container, $instance);
+    public function __invoke(ContainerInterface $container, $instance) : void;
 }
diff --git a/src/InitializerInterface.php b/src/InitializerInterface.php
index 23c5ac20..2f5f3646 100644
--- a/src/InitializerInterface.php
+++ b/src/InitializerInterface.php
@@ -32,7 +32,7 @@ interface InitializerInterface extends Initializer\InitializerInterface
     /**
      * Initialize
      *
-     * @param $instance
+     * @param mixed $instance
      * @param ServiceLocatorInterface $serviceLocator
      * @return mixed
      */
diff --git a/src/PluginManagerInterface.php b/src/PluginManagerInterface.php
index 7392195e..ddd7c53f 100644
--- a/src/PluginManagerInterface.php
+++ b/src/PluginManagerInterface.php
@@ -20,10 +20,9 @@ interface PluginManagerInterface extends ServiceLocatorInterface
      * Validate an instance
      *
      * @param  object $instance
-     * @return void
      * @throws InvalidServiceException If created instance does not respect the
      *     constraint on type imposed by the plugin manager
      * @throws ContainerException if any other error occurs
      */
-    public function validate($instance);
+    public function validate($instance) : void;
 }
diff --git a/src/Proxy/LazyServiceFactory.php b/src/Proxy/LazyServiceFactory.php
index 9f2c2446..351490ac 100644
--- a/src/Proxy/LazyServiceFactory.php
+++ b/src/Proxy/LazyServiceFactory.php
@@ -9,10 +9,10 @@
 
 use ProxyManager\Factory\LazyLoadingValueHolderFactory;
 use ProxyManager\Proxy\LazyLoadingInterface;
+use ProxyManager\Proxy\VirtualProxyInterface;
 use Psr\Container\ContainerInterface;
 use Zend\ServiceManager\Exception;
 use Zend\ServiceManager\Factory\DelegatorFactoryInterface;
-
 use function sprintf;
 
 /**
@@ -24,7 +24,7 @@
 final class LazyServiceFactory implements DelegatorFactoryInterface
 {
     /**
-     * @var \ProxyManager\Factory\LazyLoadingValueHolderFactory
+     * @var LazyLoadingValueHolderFactory
      */
     private $proxyFactory;
 
@@ -47,10 +47,14 @@ public function __construct(LazyLoadingValueHolderFactory $proxyFactory, array $
     /**
      * {@inheritDoc}
      *
-     * @return \ProxyManager\Proxy\VirtualProxyInterface
+     * @return VirtualProxyInterface
      */
-    public function __invoke(ContainerInterface $container, $name, callable $callback, array $options = null)
-    {
+    public function __invoke(
+        ContainerInterface $container,
+        string $name,
+        callable $callback,
+        array $options = null
+    ) : VirtualProxyInterface {
         $initializer = function (&$wrappedInstance, LazyLoadingInterface $proxy) use ($callback) {
             $proxy->setProxyInitializer(null);
             $wrappedInstance = $callback();
diff --git a/src/ServiceLocatorInterface.php b/src/ServiceLocatorInterface.php
index ffcfe08d..37328a0d 100644
--- a/src/ServiceLocatorInterface.php
+++ b/src/ServiceLocatorInterface.php
@@ -27,5 +27,5 @@ interface ServiceLocatorInterface extends ContainerInterface
      *     to create the instance.
      * @throws ContainerExceptionInterface if any other error occurs
      */
-    public function build($name, array $options = null);
+    public function build(string $name, array $options = null);
 }
diff --git a/src/ServiceManager.php b/src/ServiceManager.php
index e4d0c48f..513faaa0 100644
--- a/src/ServiceManager.php
+++ b/src/ServiceManager.php
@@ -238,7 +238,7 @@ public function get($name)
     /**
      * {@inheritDoc}
      */
-    public function build($name, array $options = null)
+    public function build(string $name, array $options = null)
     {
         // We never cache when using "build".
         $name = $this->aliases[$name] ?? $name;
@@ -248,7 +248,7 @@ public function build($name, array $options = null)
     /**
      * {@inheritDoc}
      */
-    public function has($name)
+    public function has($name) : bool
     {
         // Check services and factories first to speedup the most common requests.
         if (isset($this->services[$name]) || isset($this->factories[$name])) {
@@ -285,20 +285,16 @@ public function has($name)
 
     /**
      * Indicate whether or not the instance is immutable.
-     *
-     * @param bool $flag
      */
-    public function setAllowOverride($flag)
+    public function setAllowOverride(bool $flag) : void
     {
         $this->allowOverride = (bool) $flag;
     }
 
     /**
      * Retrieve the flag indicating immutability status.
-     *
-     * @return bool
      */
-    public function getAllowOverride()
+    public function getAllowOverride() : bool
     {
         return $this->allowOverride;
     }
@@ -343,7 +339,7 @@ public function getAllowOverride()
      *     override flag has been toggled off, and a service instance
      *     exists for a given service.
      */
-    public function configure(array $config)
+    public function configure(array $config) : self
     {
         // This is a bulk update/initial configuration,
         // so we check all definitions up front.
@@ -414,7 +410,7 @@ public function configure(array $config)
      * @throws ContainerModificationsNotAllowedException if $alias already
      *     exists as a service and overrides are disallowed.
      */
-    public function setAlias($alias, $target)
+    public function setAlias(string $alias, string $target) : void
     {
         if (isset($this->services[$alias]) && ! $this->allowOverride) {
             throw ContainerModificationsNotAllowedException::fromExistingService($alias);
@@ -432,7 +428,7 @@ public function setAlias($alias, $target)
      * @throws ContainerModificationsNotAllowedException if $name already
      *     exists as a service and overrides are disallowed.
      */
-    public function setInvokableClass($name, $class = null)
+    public function setInvokableClass(string $name, string $class = null) : void
     {
         if (isset($this->services[$name]) && ! $this->allowOverride) {
             throw ContainerModificationsNotAllowedException::fromExistingService($name);
@@ -450,7 +446,7 @@ public function setInvokableClass($name, $class = null)
      * @throws ContainerModificationsNotAllowedException if $name already
      *     exists as a service and overrides are disallowed.
      */
-    public function setFactory($name, $factory)
+    public function setFactory(string $name, $factory) : void
     {
         if (isset($this->services[$name]) && ! $this->allowOverride) {
             throw ContainerModificationsNotAllowedException::fromExistingService($name);
@@ -466,7 +462,7 @@ public function setFactory($name, $factory)
      * @param null|string $class Class to which to map; if not provided, $name
      *     will be used for the mapping.
      */
-    public function mapLazyService($name, $class = null)
+    public function mapLazyService(string $name, string $class = null) : void
     {
         $this->configure(['lazy_services' => ['class_map' => [$name => $class ?: $name]]]);
     }
@@ -477,7 +473,7 @@ public function mapLazyService($name, $class = null)
      * @param string|Factory\AbstractFactoryInterface $factory Abstract factory
      *     instance or class name.
      */
-    public function addAbstractFactory($factory)
+    public function addAbstractFactory($factory) : void
     {
         $this->resolveAbstractFactoryInstance($factory);
     }
@@ -489,7 +485,7 @@ public function addAbstractFactory($factory)
      * @param string|callable|Factory\DelegatorFactoryInterface $factory Delegator
      *     factory to assign.
      */
-    public function addDelegator($name, $factory)
+    public function addDelegator(string $name, $factory) : void
     {
         $this->configure(['delegators' => [$name => [$factory]]]);
     }
@@ -499,7 +495,7 @@ public function addDelegator($name, $factory)
      *
      * @param string|callable|Initializer\InitializerInterface $initializer
      */
-    public function addInitializer($initializer)
+    public function addInitializer($initializer) : void
     {
         $this->configure(['initializers' => [$initializer]]);
     }
@@ -508,11 +504,11 @@ public function addInitializer($initializer)
      * Map a service.
      *
      * @param string $name Service name
-     * @param array|object $service
+     * @param mixed $service
      * @throws ContainerModificationsNotAllowedException if $name already
      *     exists as a service and overrides are disallowed.
      */
-    public function setService($name, $service)
+    public function setService(string $name, $service) : void
     {
         if (isset($this->services[$name]) && ! $this->allowOverride) {
             throw ContainerModificationsNotAllowedException::fromExistingService($name);
@@ -528,7 +524,7 @@ public function setService($name, $service)
      * @throws ContainerModificationsNotAllowedException if $name already
      *     exists as a service and overrides are disallowed.
      */
-    public function setShared($name, $flag)
+    public function setShared(string $name, bool $flag) : void
     {
         if (isset($this->services[$name]) && ! $this->allowOverride) {
             throw ContainerModificationsNotAllowedException::fromExistingService($name);
@@ -542,7 +538,7 @@ public function setShared($name, $flag)
      *
      * @param string[]|Initializer\InitializerInterface[]|callable[] $initializers
      */
-    private function resolveInitializers(array $initializers)
+    private function resolveInitializers(array $initializers) : void
     {
         foreach ($initializers as $initializer) {
             if (is_string($initializer) && class_exists($initializer)) {
@@ -565,7 +561,7 @@ private function resolveInitializers(array $initializers)
      * @return callable
      * @throws ServiceNotFoundException
      */
-    private function getFactory($name)
+    private function getFactory(string $name) : callable
     {
         $factory = $this->factories[$name] ?? null;
 
@@ -601,7 +597,7 @@ private function getFactory($name)
      * @param  null|array $options
      * @return object
      */
-    private function createDelegatorFromName($name, array $options = null)
+    private function createDelegatorFromName(string $name, array $options = null)
     {
         $creationCallback = function () use ($name, $options) {
             // Code is inlined for performance reason, instead of abstracting the creation
@@ -661,7 +657,7 @@ private function createDelegatorFromName($name, array $options = null)
      *     creating a service.
      * @throws ExceptionInterface if any other error occurs
      */
-    private function doCreate($resolvedName, array $options = null)
+    private function doCreate(string $resolvedName, array $options = null)
     {
         try {
             if (! isset($this->delegators[$resolvedName])) {
@@ -698,7 +694,7 @@ private function doCreate($resolvedName, array $options = null)
      * @throws ServiceNotCreatedException when the lazy service class_map
      *     configuration is missing
      */
-    private function createLazyServiceDelegatorFactory()
+    private function createLazyServiceDelegatorFactory() : Proxy\LazyServiceFactory
     {
         if ($this->lazyServicesDelegator) {
             return $this->lazyServicesDelegator;
@@ -745,7 +741,7 @@ private function createLazyServiceDelegatorFactory()
      *
      * @param array $invokables
      */
-    private function createAliasesAndFactoriesForInvokables(array $invokables)
+    private function createAliasesAndFactoriesForInvokables(array $invokables) : void
     {
         foreach ($invokables as $name => $class) {
             $this->factories[$class] = Factory\InvokableFactory::class;
@@ -769,7 +765,7 @@ private function createAliasesAndFactoriesForInvokables(array $invokables)
      * @throws ContainerModificationsNotAllowedException if any
      *     service key is invalid.
      */
-    private function validateServiceNames(array $config)
+    private function validateServiceNames(array $config) : void
     {
         if ($this->allowOverride || ! $this->configured) {
             return;
@@ -844,7 +840,7 @@ private function validateServiceNames(array $config)
      * @param string $alias
      * @param string $target
      */
-    private function mapAliasToTarget($alias, $target)
+    private function mapAliasToTarget(string $alias, string $target) : void
     {
         // $target is either an alias or something else
         // if it is an alias, resolve it
@@ -883,7 +879,7 @@ private function mapAliasToTarget($alias, $target)
      * @see mapAliasToTarget above
      *
      */
-    private function mapAliasesToTargets()
+    private function mapAliasesToTargets() : void
     {
         $tagged = [];
         foreach ($this->aliases as $alias => $target) {
@@ -927,9 +923,8 @@ private function mapAliasesToTargets()
      * Instantiate abstract factories in order to avoid checks during service construction.
      *
      * @param string|Factory\AbstractFactoryInterface $abstractFactories
-     * @return void
      */
-    private function resolveAbstractFactoryInstance($abstractFactory)
+    private function resolveAbstractFactoryInstance($abstractFactory) : void
     {
         if (is_string($abstractFactory) && class_exists($abstractFactory)) {
             // Cached string factory name
diff --git a/src/Tool/ConfigDumper.php b/src/Tool/ConfigDumper.php
index e4cb5a63..7c9e8b11 100644
--- a/src/Tool/ConfigDumper.php
+++ b/src/Tool/ConfigDumper.php
@@ -56,13 +56,9 @@ public function __construct(ContainerInterface $container = null)
     }
 
     /**
-     * @param array $config
-     * @param string $className
-     * @param bool $ignoreUnresolved
-     * @return array
      * @throws InvalidArgumentException for invalid $className
      */
-    public function createDependencyConfig(array $config, $className, $ignoreUnresolved = false)
+    public function createDependencyConfig(array $config, string $className, bool $ignoreUnresolved = false) : array
     {
         $this->validateClassName($className);
 
@@ -125,35 +121,24 @@ function (ReflectionParameter $argument) {
      * @throws InvalidArgumentException if class name is not a string or does
      *     not exist.
      */
-    private function validateClassName($className)
+    private function validateClassName(string $className) : void
     {
-        if (! is_string($className)) {
-            throw new InvalidArgumentException('Class name must be a string, ' . gettype($className) . ' given');
-        }
-
         if (! class_exists($className) && ! interface_exists($className)) {
             throw new InvalidArgumentException('Cannot find class or interface with name ' . $className);
         }
     }
 
-    /**
-     * @param array $config
-     * @param string $className
-     * @return array
-     */
-    private function createInvokable(array $config, $className)
+    private function createInvokable(array $config, string $className) : array
     {
         $config[ConfigAbstractFactory::class][$className] = [];
         return $config;
     }
 
     /**
-     * @param array $config
-     * @return array
      * @throws InvalidArgumentException if ConfigAbstractFactory configuration
      *     value is not an array.
      */
-    public function createFactoryMappingsFromConfig(array $config)
+    public function createFactoryMappingsFromConfig(array $config) : array
     {
         if (! array_key_exists(ConfigAbstractFactory::class, $config)) {
             return $config;
@@ -173,12 +158,7 @@ public function createFactoryMappingsFromConfig(array $config)
         return $config;
     }
 
-    /**
-     * @param array $config
-     * @param string $className
-     * @return array
-     */
-    public function createFactoryMappings(array $config, $className)
+    public function createFactoryMappings(array $config, string $className) : array
     {
         $this->validateClassName($className);
 
@@ -193,11 +173,7 @@ public function createFactoryMappings(array $config, $className)
         return $config;
     }
 
-    /**
-     * @param array $config
-     * @return string
-     */
-    public function dumpConfigFile(array $config)
+    public function dumpConfigFile(array $config) : string
     {
         $prepared = $this->prepareConfig($config);
         return sprintf(
@@ -208,12 +184,7 @@ public function dumpConfigFile(array $config)
         );
     }
 
-    /**
-     * @param array|Traversable $config
-     * @param int $indentLevel
-     * @return string
-     */
-    private function prepareConfig($config, $indentLevel = 1)
+    private function prepareConfig(iterable $config, int $indentLevel = 1) : string
     {
         $indent = str_repeat(' ', $indentLevel * 4);
         $entries = [];
@@ -238,9 +209,8 @@ private function prepareConfig($config, $indentLevel = 1)
 
     /**
      * @param string|int|null $key
-     * @return null|string
      */
-    private function createConfigKey($key)
+    private function createConfigKey($key) : ?string
     {
         if (is_string($key) && class_exists($key)) {
             return sprintf('\\%s::class', $key);
@@ -255,10 +225,8 @@ private function createConfigKey($key)
 
     /**
      * @param mixed $value
-     * @param int $indentLevel
-     * @return string
      */
-    private function createConfigValue($value, $indentLevel)
+    private function createConfigValue($value, int $indentLevel) : string
     {
         if (is_array($value) || $value instanceof Traversable) {
             return $this->prepareConfig($value, $indentLevel + 1);
diff --git a/src/Tool/ConfigDumperCommand.php b/src/Tool/ConfigDumperCommand.php
index 60f44847..afa0a61c 100644
--- a/src/Tool/ConfigDumperCommand.php
+++ b/src/Tool/ConfigDumperCommand.php
@@ -7,9 +7,9 @@
 
 namespace Zend\ServiceManager\Tool;
 
+use stdClass;
 use Zend\ServiceManager\Exception;
 use Zend\Stdlib\ConsoleHelper;
-
 use function array_shift;
 use function class_exists;
 use function dirname;
@@ -60,10 +60,7 @@ class ConfigDumperCommand
      */
     private $scriptName;
 
-    /**
-     * @param string $scriptName
-     */
-    public function __construct($scriptName = self::DEFAULT_SCRIPT_NAME, ConsoleHelper $helper = null)
+    public function __construct(string $scriptName = self::DEFAULT_SCRIPT_NAME, ConsoleHelper $helper = null)
     {
         $this->scriptName = $scriptName;
         $this->helper = $helper ?: new ConsoleHelper();
@@ -73,7 +70,7 @@ public function __construct($scriptName = self::DEFAULT_SCRIPT_NAME, ConsoleHelp
      * @param array $args Argument list, minus script name
      * @return int Exit status
      */
-    public function __invoke(array $args)
+    public function __invoke(array $args) : int
     {
         $arguments = $this->parseArgs($args);
 
@@ -117,11 +114,7 @@ public function __invoke(array $args)
         return 0;
     }
 
-    /**
-     * @param array $args
-     * @return \stdClass
-     */
-    private function parseArgs(array $args)
+    private function parseArgs(array $args) : stdClass
     {
         if (! $args) {
             return $this->createHelpArgument();
@@ -186,7 +179,7 @@ private function parseArgs(array $args)
      * @param resource $resource Defaults to STDOUT
      * @return void
      */
-    private function help($resource = STDOUT)
+    private function help($resource = STDOUT) : void
     {
         $this->helper->writeLine(sprintf(
             self::HELP_TEMPLATE,
@@ -201,10 +194,15 @@ private function help($resource = STDOUT)
      * @param array $config Parsed configuration.
      * @param string $class Name of class to reflect.
      * @param bool $ignoreUnresolved If to ignore classes with unresolved direct dependencies.
-     * @return \stdClass
+     * @return stdClass
      */
-    private function createArguments($command, $configFile, $config, $class, $ignoreUnresolved)
-    {
+    private function createArguments(
+        string $command,
+        string $configFile,
+        array $config,
+        string $class,
+        bool $ignoreUnresolved
+    ) : stdClass {
         return (object) [
             'command'          => $command,
             'configFile'       => $configFile,
@@ -214,11 +212,7 @@ private function createArguments($command, $configFile, $config, $class, $ignore
         ];
     }
 
-    /**
-     * @param string $message
-     * @return \stdClass
-     */
-    private function createErrorArgument($message)
+    private function createErrorArgument(string $message) : stdClass
     {
         return (object) [
             'command' => self::COMMAND_ERROR,
@@ -226,10 +220,7 @@ private function createErrorArgument($message)
         ];
     }
 
-    /**
-     * @return \stdClass
-     */
-    private function createHelpArgument()
+    private function createHelpArgument() : stdClass
     {
         return (object) [
             'command' => self::COMMAND_HELP,
diff --git a/src/Tool/FactoryCreator.php b/src/Tool/FactoryCreator.php
index f3f19ec7..e094048a 100644
--- a/src/Tool/FactoryCreator.php
+++ b/src/Tool/FactoryCreator.php
@@ -49,11 +49,7 @@ public function __invoke(ContainerInterface $container, $requestedName, array $o
 
 EOT;
 
-    /**
-     * @param string $className
-     * @return string
-     */
-    public function createFactory($className)
+    public function createFactory(string $className) : string
     {
         $class = $this->getClassName($className);
 
@@ -68,21 +64,13 @@ public function createFactory($className)
         );
     }
 
-    /**
-     * @param $className
-     * @return string
-     */
-    private function getClassName($className)
+    private function getClassName(string $className) : string
     {
         $class = substr($className, strrpos($className, '\\') + 1);
         return $class;
     }
 
-    /**
-     * @param string $className
-     * @return array
-     */
-    private function getConstructorParameters($className)
+    private function getConstructorParameters(string $className) : array
     {
         $reflectionClass = new ReflectionClass($className);
 
@@ -124,11 +112,7 @@ function (ReflectionParameter $argument) {
         }, $constructorParameters);
     }
 
-    /**
-     * @param string $className
-     * @return string
-     */
-    private function createArgumentString($className)
+    private function createArgumentString(string $className) : string
     {
         $arguments = array_map(function ($dependency) {
             return sprintf('$container->get(\\%s::class)', $dependency);
diff --git a/src/Tool/FactoryCreatorCommand.php b/src/Tool/FactoryCreatorCommand.php
index 3bcffb85..c2386376 100644
--- a/src/Tool/FactoryCreatorCommand.php
+++ b/src/Tool/FactoryCreatorCommand.php
@@ -7,9 +7,9 @@
 
 namespace Zend\ServiceManager\Tool;
 
+use stdClass;
 use Zend\ServiceManager\Exception;
 use Zend\Stdlib\ConsoleHelper;
-
 use function array_shift;
 use function class_exists;
 use function in_array;
@@ -48,11 +48,7 @@ class FactoryCreatorCommand
      */
     private $scriptName;
 
-    /**
-     * @param string $scriptName
-     * @param ConsoleHelper $helper
-     */
-    public function __construct($scriptName = self::DEFAULT_SCRIPT_NAME, ConsoleHelper $helper = null)
+    public function __construct(string $scriptName = self::DEFAULT_SCRIPT_NAME, ConsoleHelper $helper = null)
     {
         $this->scriptName = $scriptName;
         $this->helper = $helper ?: new ConsoleHelper();
@@ -62,7 +58,7 @@ public function __construct($scriptName = self::DEFAULT_SCRIPT_NAME, ConsoleHelp
      * @param array $args Argument list, minus script name
      * @return int Exit status
      */
-    public function __invoke(array $args)
+    public function __invoke(array $args) : int
     {
         $arguments = $this->parseArgs($args);
 
@@ -97,11 +93,7 @@ public function __invoke(array $args)
         return 0;
     }
 
-    /**
-     * @param array $args
-     * @return \stdClass
-     */
-    private function parseArgs(array $args)
+    private function parseArgs(array $args) : stdClass
     {
         if (! $args) {
             return $this->createArguments(self::COMMAND_HELP);
@@ -129,7 +121,7 @@ private function parseArgs(array $args)
      * @param resource $resource Defaults to STDOUT
      * @return void
      */
-    private function help($resource = STDOUT)
+    private function help($resource = STDOUT) : void
     {
         $this->helper->writeLine(sprintf(
             self::HELP_TEMPLATE,
@@ -138,12 +130,10 @@ private function help($resource = STDOUT)
     }
 
     /**
-     * @param string $command
      * @param string|null $class Name of class to reflect.
      * @param string|null $error Error message, if any.
-     * @return \stdClass
      */
-    private function createArguments($command, $class = null, $error = null)
+    private function createArguments(string $command, string $class = null, string $error = null) : stdClass
     {
         return (object) [
             'command' => $command,
diff --git a/test/AbstractFactory/TestAsset/ClassWithScalarDependencyDefiningDefaultValue.php b/test/AbstractFactory/TestAsset/ClassWithScalarDependencyDefiningDefaultValue.php
index 39294e99..fca3e827 100644
--- a/test/AbstractFactory/TestAsset/ClassWithScalarDependencyDefiningDefaultValue.php
+++ b/test/AbstractFactory/TestAsset/ClassWithScalarDependencyDefiningDefaultValue.php
@@ -11,10 +11,7 @@ class ClassWithScalarDependencyDefiningDefaultValue
 {
     public $foo;
 
-    /**
-     * @param string $foo
-     */
-    public function __construct($foo = 'bar')
+    public function __construct(string $foo = 'bar')
     {
         $this->foo = $foo;
     }
diff --git a/test/ConfigTest.php b/test/ConfigTest.php
index b2257d01..ffae666e 100644
--- a/test/ConfigTest.php
+++ b/test/ConfigTest.php
@@ -104,10 +104,11 @@ public function testPassesKnownServiceConfigKeysToServiceManagerWithConfigMethod
         ];
 
         $services = $this->prophesize(ServiceManager::class);
-        $services->configure($expected)->willReturn('CALLED');
+        $object = $services->reveal();
+        $services->configure($expected)->willReturn($object);
 
         $configuration = new Config($config);
-        self::assertEquals('CALLED', $configuration->configureServiceManager($services->reveal()));
+        self::assertEquals($object, $configuration->configureServiceManager($object));
 
         return [
             'array'  => $expected,
diff --git a/test/Exception/CyclicAliasExceptionTest.php b/test/Exception/CyclicAliasExceptionTest.php
index bedf1352..fb72724b 100644
--- a/test/Exception/CyclicAliasExceptionTest.php
+++ b/test/Exception/CyclicAliasExceptionTest.php
@@ -20,10 +20,8 @@ class CyclicAliasExceptionTest extends TestCase
      * @dataProvider cyclicAliasProvider
      *
      * @param string   $alias, conflicting alias key
-     * @param string[] $aliases
-     * @param string   $expectedMessage
      */
-    public function testFromCyclicAlias($alias, array $aliases, $expectedMessage)
+    public function testFromCyclicAlias(string $alias, array $aliases, string $expectedMessage)
     {
         $exception = CyclicAliasException::fromCyclicAlias($alias, $aliases);
 
@@ -36,7 +34,7 @@ public function testFromCyclicAlias($alias, array $aliases, $expectedMessage)
      *
      * @return string[][]|string[][][]
      */
-    public function cyclicAliasProvider()
+    public function cyclicAliasProvider() : array
     {
         return [
             [
@@ -113,7 +111,7 @@ public function cyclicAliasProvider()
      * @param string[] $aliases
      * @param string   $expectedMessage
      */
-    public function testFromAliasesMap(array $aliases, $expectedMessage)
+    public function testFromAliasesMap(array $aliases, string $expectedMessage)
     {
         $exception = CyclicAliasException::fromAliasesMap($aliases);
 
@@ -124,7 +122,7 @@ public function testFromAliasesMap(array $aliases, $expectedMessage)
     /**
      * @return string[][]|string[][][]
      */
-    public function aliasesProvider()
+    public function aliasesProvider() : array
     {
         return [
             'empty set' => [
diff --git a/test/TestAsset/AbstractFactoryFoo.php b/test/TestAsset/AbstractFactoryFoo.php
index 9ab36eb7..3fa2a168 100644
--- a/test/TestAsset/AbstractFactoryFoo.php
+++ b/test/TestAsset/AbstractFactoryFoo.php
@@ -12,7 +12,7 @@
 
 class AbstractFactoryFoo implements AbstractFactoryInterface
 {
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         if ($requestedName === 'foo') {
             return new Foo($options);
@@ -20,7 +20,7 @@ public function __invoke(ContainerInterface $container, $requestedName, array $o
         return false;
     }
 
-    public function canCreate(ContainerInterface $container, $requestedName)
+    public function canCreate(ContainerInterface $container, string $requestedName) : bool
     {
         return ($requestedName === 'foo');
     }
diff --git a/test/TestAsset/CallTimesAbstractFactory.php b/test/TestAsset/CallTimesAbstractFactory.php
index a14382f8..005a0337 100644
--- a/test/TestAsset/CallTimesAbstractFactory.php
+++ b/test/TestAsset/CallTimesAbstractFactory.php
@@ -17,7 +17,7 @@ class CallTimesAbstractFactory implements AbstractFactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function canCreate(ContainerInterface $container, $name)
+    public function canCreate(ContainerInterface $container, string $name) : bool
     {
         self::$callTimes++;
 
@@ -27,7 +27,7 @@ public function canCreate(ContainerInterface $container, $name)
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $className, array $options = null)
+    public function __invoke(ContainerInterface $container, string $className, array $options = null)
     {
     }
 
diff --git a/test/TestAsset/FailingAbstractFactory.php b/test/TestAsset/FailingAbstractFactory.php
index 8332cece..8e8dd1fd 100644
--- a/test/TestAsset/FailingAbstractFactory.php
+++ b/test/TestAsset/FailingAbstractFactory.php
@@ -15,7 +15,7 @@ class FailingAbstractFactory implements AbstractFactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function canCreate(ContainerInterface $container, $name)
+    public function canCreate(ContainerInterface $container, string $name) : bool
     {
         return false;
     }
@@ -23,7 +23,7 @@ public function canCreate(ContainerInterface $container, $name)
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $className, array $options = null)
+    public function __invoke(ContainerInterface $container, string $className, array $options = null)
     {
     }
 }
diff --git a/test/TestAsset/FailingExceptionWithStringAsCodeFactory.php b/test/TestAsset/FailingExceptionWithStringAsCodeFactory.php
index 27169ffe..277d291d 100644
--- a/test/TestAsset/FailingExceptionWithStringAsCodeFactory.php
+++ b/test/TestAsset/FailingExceptionWithStringAsCodeFactory.php
@@ -15,7 +15,7 @@ class FailingExceptionWithStringAsCodeFactory implements FactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         throw new ExceptionWithStringAsCode('There is an error');
     }
diff --git a/test/TestAsset/FailingFactory.php b/test/TestAsset/FailingFactory.php
index 5d2085d3..d9778673 100644
--- a/test/TestAsset/FailingFactory.php
+++ b/test/TestAsset/FailingFactory.php
@@ -15,7 +15,7 @@ class FailingFactory implements FactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         throw new \RuntimeException('There is an error');
     }
diff --git a/test/TestAsset/LenientPluginManager.php b/test/TestAsset/LenientPluginManager.php
index a98b9f2c..f5273040 100644
--- a/test/TestAsset/LenientPluginManager.php
+++ b/test/TestAsset/LenientPluginManager.php
@@ -14,7 +14,7 @@ class LenientPluginManager extends AbstractPluginManager
     /**
      * Allow anything to be considered valid.
      */
-    public function validate($instance)
+    public function validate($instance) : void
     {
         return;
     }
diff --git a/test/TestAsset/PassthroughDelegatorFactory.php b/test/TestAsset/PassthroughDelegatorFactory.php
index d0eec4b9..923ba312 100644
--- a/test/TestAsset/PassthroughDelegatorFactory.php
+++ b/test/TestAsset/PassthroughDelegatorFactory.php
@@ -16,7 +16,7 @@ class PassthroughDelegatorFactory implements DelegatorFactoryInterface
      * {@inheritDoc}
      * @see \Zend\ServiceManager\Factory\DelegatorFactoryInterface::__invoke()
      */
-    public function __invoke(ContainerInterface $container, $name, callable $callback, array $options = null)
+    public function __invoke(ContainerInterface $container, string $name, callable $callback, array $options = null)
     {
         return call_user_func($callback);
     }
diff --git a/test/TestAsset/PreDelegator.php b/test/TestAsset/PreDelegator.php
index 97e32b8a..5c5312e9 100644
--- a/test/TestAsset/PreDelegator.php
+++ b/test/TestAsset/PreDelegator.php
@@ -15,7 +15,7 @@ class PreDelegator implements DelegatorFactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $name, callable $callback, array $options = null)
+    public function __invoke(ContainerInterface $container, string $name, callable $callback, array $options = null)
     {
         if (! $container->has('config')) {
             return $callback();
diff --git a/test/TestAsset/SampleFactory.php b/test/TestAsset/SampleFactory.php
index b0e0db2d..f3ffd406 100644
--- a/test/TestAsset/SampleFactory.php
+++ b/test/TestAsset/SampleFactory.php
@@ -13,7 +13,7 @@
 class SampleFactory implements FactoryInterface
 {
 
-    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    public function __invoke(ContainerInterface $container, string $requestedName, array $options = null)
     {
         return new InvokableObject();
     }
diff --git a/test/TestAsset/SimpleAbstractFactory.php b/test/TestAsset/SimpleAbstractFactory.php
index 2c5f74df..70fc5287 100644
--- a/test/TestAsset/SimpleAbstractFactory.php
+++ b/test/TestAsset/SimpleAbstractFactory.php
@@ -15,7 +15,7 @@ class SimpleAbstractFactory implements AbstractFactoryInterface
     /**
      * {@inheritDoc}
      */
-    public function canCreate(ContainerInterface $container, $name)
+    public function canCreate(ContainerInterface $container, string $name) : bool
     {
         return true;
     }
@@ -23,7 +23,7 @@ public function canCreate(ContainerInterface $container, $name)
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $className, array $options = null)
+    public function __invoke(ContainerInterface $container, string $className, array $options = null)
     {
         if (empty($options)) {
             return new $className();
diff --git a/test/TestAsset/SimpleInitializer.php b/test/TestAsset/SimpleInitializer.php
index 9419a763..ae3334c6 100644
--- a/test/TestAsset/SimpleInitializer.php
+++ b/test/TestAsset/SimpleInitializer.php
@@ -16,7 +16,7 @@ class SimpleInitializer implements InitializerInterface
     /**
      * {@inheritDoc}
      */
-    public function __invoke(ContainerInterface $container, $instance)
+    public function __invoke(ContainerInterface $container, $instance) : void
     {
         if (! $instance instanceof stdClass) {
             return;
diff --git a/test/TestAsset/V2v3PluginManager.php b/test/TestAsset/V2v3PluginManager.php
index 8e612b79..1b23c3e3 100644
--- a/test/TestAsset/V2v3PluginManager.php
+++ b/test/TestAsset/V2v3PluginManager.php
@@ -33,7 +33,7 @@ class V2v3PluginManager extends AbstractPluginManager
     protected $sharedByDefault = false;
 
 
-    public function validate($plugin)
+    public function validate($plugin) : void
     {
         if ($plugin instanceof $this->instanceOf) {
             return;
diff --git a/test/Tool/ConfigDumperTest.php b/test/Tool/ConfigDumperTest.php
index 38ff0846..090f60ac 100644
--- a/test/Tool/ConfigDumperTest.php
+++ b/test/Tool/ConfigDumperTest.php
@@ -39,13 +39,6 @@ public function setUp()
         $this->dumper = new ConfigDumper();
     }
 
-    public function testCreateDependencyConfigExceptsIfClassNameIsNotString()
-    {
-        $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Class name must be a string, integer given');
-        $this->dumper->createDependencyConfig([], 42);
-    }
-
     public function testCreateDependencyConfigExceptsIfClassDoesNotExist()
     {
         $className = 'Dirk\Gentley\Holistic\Detective\Agency';
@@ -212,13 +205,6 @@ public function testCreateDependencyConfigWorksWithMultipleDependenciesOfSameTyp
         self::assertEquals($expectedConfig, $this->dumper->createDependencyConfig([], DoubleDependencyObject::class));
     }
 
-    public function testCreateFactoryMappingsExceptsIfClassNameIsNotString()
-    {
-        $this->expectException(InvalidArgumentException::class);
-        $this->expectExceptionMessage('Class name must be a string, integer given');
-        $this->dumper->createFactoryMappings([], 42);
-    }
-
     public function testCreateFactoryMappingsExceptsIfClassDoesNotExist()
     {
         $className = 'Dirk\Gentley\Holistic\Detective\Agency';