tests(carousel): fix false positive issues through simplification

Fixes the false positive issues by simplifying the assertions made
to verify its most basic use case (e.g. assert after automatically
sliding the first element and check if we're still on the second
element).

Author: bpas247

test/CarouselSpec.js

@@ -316,36 +316,21 @@ describe('<Carousel>', () => {
     });
 
     it('should go through the items given the specified intervals', () => {
-      const defaultInterval = 5000;
-      const intervals = [
-        1000,
-        500,
-        defaultInterval, // to test for no interval specified, it should be the default
-      ];
-      const itemsWithIntervals = [
-        <Carousel.Item key={1} interval={intervals[0]}>
-          Item 1 content
-        </Carousel.Item>,
-        <Carousel.Item key={2} interval={intervals[1]}>
-          Item 2 content
-        </Carousel.Item>,
-        <Carousel.Item key={3}>Item 3 content</Carousel.Item>,
-      ];
-
       const onSelectSpy = sinon.spy();
       mount(
-        <Carousel interval={defaultInterval} onSelect={onSelectSpy}>
-          {itemsWithIntervals}
+        <Carousel interval={1000} onSelect={onSelectSpy}>
+          <Carousel.Item interval={100}>Item 1 content</Carousel.Item>
+          <Carousel.Item>Item 2 content</Carousel.Item>
         </Carousel>,
       );
 
-      const total = intervals.reduce((sum, current) => sum + current, 0);
-      clock.tick(total * 1.1);
+      // should be long enough to handle false positive issues
+      // but short enough to not trigger auto-play to occur twice
+      // (since the interval for the second item should be `1000`)
+      clock.tick(200);
 
-      expect(onSelectSpy).to.have.been.calledThrice;
+      expect(onSelectSpy).to.have.been.calledOnce;
       expect(onSelectSpy.firstCall).to.have.been.calledWith(1);
-      expect(onSelectSpy.secondCall).to.have.been.calledWith(2);
-      expect(onSelectSpy.thirdCall).to.have.been.calledWith(0);
     });
 
     it('should stop going through items on hover and continue afterwards', () => {