fix error in addwbs file

Author: 喜喜懒羊羊

src/components/Projects/WBS/AddWBS/AddWBS.jsx

@@ -49,6 +49,7 @@ const AddWBS = props => {
                 className="btn btn-outline-primary"
                 type="button"
                 onClick={handleAddWBS}
+                data-testid="add-wbs-button"
               >
                 <i className="fa fa-plus" aria-hidden="true"></i>
               </button>

src/components/Projects/WBS/AddWBS/__tests__/AddWBS.test.jsx

@@ -66,7 +66,7 @@ describe("AddWBS component structure", () => {
   });
 
   test("button should not be in the document when the input field is empty", () => {
-    expect(screen.queryByRole('button')).toBeNull();
+    expect(screen.queryByTestId('add-wbs-button')).toBeNull();
   });
 
   test("user should be able to type in the input field", () => {
@@ -76,7 +76,7 @@ describe("AddWBS component structure", () => {
 
   test("button should appear when user types in the input field", () => {
     typeIntoInput({ input: '123' });
-    expect(screen.queryByRole('button')).not.toBeNull();
+    expect(screen.queryByTestId('add-wbs-button')).not.toBeNull();
   });
 });