[Test modernization] Modernizes DualThumb

UNRELEASED.md

@@ -28,5 +28,6 @@ Use [the changelog guidelines](https://git.io/polaris-changelog-guidelines) to f
 - Modernized tests for PageActions, Page and its components ([#4326](https://github.com/Shopify/polaris-react/pull/4326))
 - Modernized tests for FormLayout and some components of ColorPicker ([#4330](https://github.com/Shopify/polaris-react/pull/4330))
 - Modernized tests for Breadcrumbs, BulkActions, Button, ButtonGroup/Item, and ButtonGroup components([#4315](https://github.com/Shopify/polaris-react/pull/4315))
+- Modernized tests for DualThumb ([#4341](https://github.com/Shopify/polaris-react/pull/4341))
 
 ### Deprecations

src/components/RangeSlider/components/DualThumb/DualThumb.tsx

@@ -238,15 +238,9 @@ export class DualThumb extends Component<DualThumbProps, State> {
             <div
               className={trackWrapperClassName}
               onMouseDown={this.handleMouseDownTrack}
-              testID="trackWrapper"
               ref={this.trackWrapper}
             >
-              <div
-                className={styles.Track}
-                style={cssVars}
-                ref={this.track}
-                testID="track"
-              />
+              <div className={styles.Track} style={cssVars} ref={this.track} />
               <div className={styles['Track--dashed']} />
               <div
                 id={idLower}