Fix bug with Pager service when there are no items.

Author: cjcenizal

src/services/paging/pager.js

@@ -55,6 +55,14 @@ export class Pager {
   }
 
   update = () => {
+    if (this.totalItems <= 0) {
+      this.totalPages = 0;
+      this.currentPageIndex = 0;
+      this.firstItemIndex = 0;
+      this.lastItemIndex = 0;
+      return;
+    }
+
     this.totalPages = Math.ceil(this.totalItems / this.itemsPerPage);
 
     // Ensure the current page falls within our range of total pages.

src/services/paging/pager.test.js

@@ -137,4 +137,18 @@ describe('Pager', () => {
       });
     });
   });
+
+  describe('behavior', () => {
+    describe('when there are no items', () => {
+      test('getFirstItemIndex defaults to 0', () => {
+        const pager = new Pager(0, 20);
+        expect(pager.getFirstItemIndex()).toBe(0);
+      });
+
+      test('getLastItemIndex defaults to 0', () => {
+        const pager = new Pager(0, 20);
+        expect(pager.getLastItemIndex()).toBe(0);
+      });
+    });
+  });
 });