Add Psalm

At a level of strictness the project can currently meet

.travis.yml

@@ -8,6 +8,7 @@ before_script:
 script:
   - php vendor/bin/phpunit --coverage-clover=coverage.clover
   - php vendor/bin/phpstan analyse --no-interaction
+  - php vendor/bin/psalm
 after_script:
   - wget https://scrutinizer-ci.com/ocular.phar
   - php ocular.phar code-coverage:upload --format=php-clover coverage.clover

composer.json

@@ -25,7 +25,8 @@
         "laminas/laminas-diactoros": "~1.0",
         "phpstan/phpstan": "^0.12.14",
         "phpunit/phpunit": "~7.0",
-        "roave/security-advisories": "dev-master"
+        "roave/security-advisories": "dev-master",
+        "vimeo/psalm": "^3.9"
     },
     "autoload": {
         "psr-4": {

psalm.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<psalm
+    totallyTyped="false"
+    errorLevel="5"
+    resolveFromConfigFile="true"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xmlns="https://getpsalm.org/schema/config"
+    xsi:schemaLocation="https://getpsalm.org/schema/config vendor/vimeo/psalm/config.xsd"
+>
+    <projectFiles>
+        <directory name="src" />
+        <directory name="tests"/>
+        <ignoreFiles>
+            <directory name="vendor" />
+        </ignoreFiles>
+    </projectFiles>
+</psalm>

src/RelayBuilder.php

@@ -10,6 +10,8 @@
  */
 namespace Relay;
 
+use ArrayObject;
+use Traversable;
 
 /**
  *
@@ -24,7 +26,7 @@ class RelayBuilder
      *
      * A callable to convert queue entries to callables in the Runner.
      *
-     * @var callable|ResolverInterface
+     * @var callable
      *
      */
     protected $resolver;
@@ -33,7 +35,7 @@ class RelayBuilder
      *
      * Constructor.
      *
-     * @param callable|ResolverInterface $resolver A callable to convert a queue entry to
+     * @param callable $resolver A callable to convert a queue entry to
      * a callable|MiddlewareInterface in the Runner.
      *
      */
@@ -46,7 +48,7 @@ public function __construct(callable $resolver = null)
      *
      * Creates a new Relay with the specified queue for its Runner objects.
      *
-     * @param array|ArrayObject|GetArrayCopyInterface|Traversable $queue The
+     * @param array|ArrayObject|Traversable $queue The
      * queue specification.
      *
      * @return Relay

tests/RelayBuilderTest.php

@@ -48,7 +48,7 @@ public function testInvalidArgument()
 
     public function testEmptyQueue()
     {
-        $this->expectException(InvalidArgumentException::CLASS);
+        $this->expectException(InvalidArgumentException::class);
         $this->expectExceptionMessage('$queue cannot be empty');
 
         $this->relayBuilder->newInstance([]);

tests/RelayTest.php

@@ -21,7 +21,7 @@ protected function setUp()
         };
     }
 
-    protected function assertRelay($relay)
+    protected function assertRelay(Relay $relay)
     {
         FakeMiddleware::$count = 0;
 
@@ -60,23 +60,26 @@ public function testTraversableQueue()
         $this->assertRelay(new Relay($queue));
     }
 
+    /**
+     * @psalm-suppress InvalidArgument
+     */
     public function testBadQueue()
     {
-        $this->expectException(TypeError::CLASS);
+        $this->expectException(TypeError::class);
         new Relay('bad');
     }
 
     public function testEmptyQueue()
     {
-        $this->expectException(InvalidArgumentException::CLASS);
+        $this->expectException(InvalidArgumentException::class);
         $this->expectExceptionMessage('$queue cannot be empty');
 
         new Relay([]);
     }
 
     public function testQueueWithInvalidEntry()
     {
-        $this->expectException(RuntimeException::CLASS);
+        $this->expectException(RuntimeException::class);
         $this->expectExceptionMessage(
             "Invalid middleware queue entry: bad. Middleware must either be callable or implement Psr\Http\Server\MiddlewareInterface."
         );
@@ -88,9 +91,9 @@ public function testQueueWithInvalidEntry()
     public function testResolverEntries()
     {
         $queue = [
-            FakeMiddleware::CLASS,
-            FakeMiddleware::CLASS,
-            FakeMiddleware::CLASS,
+            FakeMiddleware::class,
+            FakeMiddleware::class,
+            FakeMiddleware::class,
             $this->responder,
         ];