1 files changed, 53 insertions, 1 deletions
diff --git a/spec/javascripts/lib/utils/dom_utils_spec.js b/spec/javascripts/lib/utils/dom_utils_spec.js
index 1fb2e4584a0..2bcf37f35c7 100644
--- a/spec/javascripts/lib/utils/dom_utils_spec.js
+++ b/spec/javascripts/lib/utils/dom_utils_spec.js
@@ -1,4 +1,6 @@
-import { addClassIfElementExists } from '~/lib/utils/dom_utils';
+import { addClassIfElementExists, canScrollUp, canScrollDown } from '~/lib/utils/dom_utils';
+
+const TEST_MARGIN = 5;
 
 describe('DOM Utils', () => {
   describe('addClassIfElementExists', () => {
@@ -34,4 +36,54 @@ describe('DOM Utils', () => {
       addClassIfElementExists(childElement, className);
     });
   });
+
+  describe('canScrollUp', () => {
+    [1, 100].forEach(scrollTop => {
+      it(`is true if scrollTop is > 0 (${scrollTop})`, () => {
+        expect(canScrollUp({ scrollTop })).toBe(true);
+      });
+    });
+
+    [0, -10].forEach(scrollTop => {
+      it(`is false if scrollTop is <= 0 (${scrollTop})`, () => {
+        expect(canScrollUp({ scrollTop })).toBe(false);
+      });
+    });
+
+    it('is true if scrollTop is > margin', () => {
+      expect(canScrollUp({ scrollTop: TEST_MARGIN + 1 }, TEST_MARGIN)).toBe(true);
+    });
+
+    it('is false if scrollTop is <= margin', () => {
+      expect(canScrollUp({ scrollTop: TEST_MARGIN }, TEST_MARGIN)).toBe(false);
+    });
+  });
+
+  describe('canScrollDown', () => {
+    let element;
+
+    beforeEach(() => {
+      element = { scrollTop: 7, offsetHeight: 22, scrollHeight: 30 };
+    });
+
+    it('is true if element can be scrolled down', () => {
+      expect(canScrollDown(element)).toBe(true);
+    });
+
+    it('is false if element cannot be scrolled down', () => {
+      element.scrollHeight -= 1;
+
+      expect(canScrollDown(element)).toBe(false);
+    });
+
+    it('is true if element can be scrolled down, with margin given', () => {
+      element.scrollHeight += TEST_MARGIN;
+
+      expect(canScrollDown(element, TEST_MARGIN)).toBe(true);
+    });
+
+    it('is false if element cannot be scrolled down, with margin given', () => {
+      expect(canScrollDown(element, TEST_MARGIN)).toBe(false);
+    });
+  });
 });