[bugfix] Tabs: incorrect line position in some cases (#3961)

test/utils/event.ts

@@ -0,0 +1,56 @@
+import Vue from 'vue';
+import { Wrapper } from '@vue/test-utils';
+
+function getTouch(el: HTMLElement | Window, x: number, y: number) {
+  return {
+    identifier: Date.now(),
+    target: el,
+    pageX: x,
+    pageY: y,
+    clientX: x,
+    clientY: y,
+    radiusX: 2.5,
+    radiusY: 2.5,
+    rotationAngle: 10,
+    force: 0.5
+  };
+}
+
+// Trigger pointer/touch event
+export function trigger(
+  wrapper: Wrapper<Vue> | HTMLElement | Window,
+  eventName: string,
+  x: number = 0,
+  y: number = 0,
+  options: any = {}
+) {
+  const el = 'element' in wrapper ? wrapper.element : wrapper;
+  const touchList = options.touchList || [getTouch(el, x, y)];
+
+  if (options.x || options.y) {
+    touchList.push(getTouch(el, options.x, options.y));
+  }
+
+  const event = document.createEvent('CustomEvent');
+  event.initCustomEvent(eventName, true, true, {});
+
+  Object.assign(event, {
+    clientX: x,
+    clientY: y,
+    touches: touchList,
+    targetTouches: touchList,
+    changedTouches: touchList
+  });
+
+  el.dispatchEvent(event);
+}
+
+// simulate drag gesture
+export function triggerDrag(el: Wrapper<Vue> | HTMLElement, x = 0, y = 0): void {
+  trigger(el, 'touchstart', 0, 0);
+  trigger(el, 'touchmove', x / 4, y / 4);
+  trigger(el, 'touchmove', x / 3, y / 3);
+  trigger(el, 'touchmove', x / 2, y / 2);
+  trigger(el, 'touchmove', x, y);
+  trigger(el, 'touchend', x, y);
+}