add test for equal results (amend PR facundoolano#677)

For detection of facundoolano#676 (less than actual number of requests returned, different response count on each request).

Using app with large number of reviews sorted by helpfulness (assuming this set does not change as frequently as just reviews), num: 1500 is reasonably fast and we get 2 x 10 paged requests (of 150 results) that ought to prove paging works.

test/lib.reviews.js

@@ -102,4 +102,25 @@ describe('Reviews method', () => {
     assert.isNotNull(secondPaginationToken);
     assert.notDeepEqual(data, dataSecondPage);
   });
+
+  it('should get same set of reviews on each run', async () => {
+    const firstPageReviews = await gplay.reviews({
+      appId: 'com.facebook.katana',
+      num: 1500,
+      sort: constants.sort.HELPFULNESS
+    });
+    const { data } = firstPageReviews;
+
+    assert.equal(data.length, 1500);
+
+    const secondPageReviews = await gplay.reviews({
+      appId: 'com.facebook.katana',
+      num: 1500,
+      sort: constants.sort.HELPFULNESS
+    });
+    const { data: dataSecondPage } = secondPageReviews;
+
+    assert.equal(dataSecondPage.length, 1500);
+    assert.deepEqual(data, dataSecondPage);
+  });
 });