Move stub to helper file

Define containers once

Create new instance for each test

Linting

Linting

Add assertion, update stub

Use expecteds

Move expecteds up in scope

Use triggerEvent helper

scripts/test/helper.js

@@ -74,3 +74,40 @@ export function triggerEvent(element, type, data = {}) {
   element.dispatchEvent(event);
   return event;
 }
+
+/**
+ * A stub of the Plugin class
+ *
+ * @class PluginStub
+ */
+export class PluginStub {
+
+  /**
+   * Constructor.
+   *
+   * @param {Draggable} draggable
+   */
+  constructor(draggable) {
+    this.attachWasCalled = false;
+    this.detachWasCalled = false;
+    this.draggable = draggable;
+    this.numTimesAttachCalled = 0;
+    this.numTimesDetachCalled = 0;
+  }
+
+  /**
+   * Set a testable property when `attach` is called
+   */
+  attach() {
+    this.attachWasCalled = true;
+    this.numTimesAttachCalled++;
+  }
+
+  /**
+   * Set a testable property when `detach` is called
+   */
+  detach() {
+    this.detachWasCalled = true;
+    this.numTimesDetachCalled++;
+  }
+}