diff --git a/.gitignore b/.gitignore
index fd27a97..6d77a74 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 build
 composer.lock
+coverage
 phpunit.xml
 vendor
 humbug.json
diff --git a/test/ProducerTraitTest.php b/test/ProducerTraitTest.php
index 579f3c0..c02d474 100644
--- a/test/ProducerTraitTest.php
+++ b/test/ProducerTraitTest.php
@@ -186,4 +186,30 @@ class ProducerTraitTest extends TestCase {
         $this->assertTrue($invoked);
         throw $reason;
     }
+
+    /**
+     * @expectedException \Error
+     * @expectedExceptionMessage The prior promise returned must resolve before invoking this method again
+     */
+    public function testDoubleAdvance() {
+        $this->producer->advance();
+        $this->producer->advance();
+    }
+
+    /**
+     * @expectedException \Error
+     * @expectedExceptionMessage Promise returned from advance() must resolve before calling this method
+     */
+    public function testGetCurrentBeforeAdvance() {
+        $this->producer->getCurrent();
+    }
+
+    /**
+     * @expectedException \Error
+     * @expectedExceptionMessage Iterator has already been completed
+     */
+    public function testDoubleComplete() {
+        $this->producer->complete();
+        $this->producer->complete();
+    }
 }