Add unittests

src/filters/bgImage/bgImage.spec.js

@@ -0,0 +1,11 @@
+import { expect } from 'chai';
+import bgImageFilter from './index';
+
+describe('bgImage Filter', () => {
+    it('create style o object', () => {
+        const url = 'http://via.placeholder.com/400x400';
+        const style = bgImageFilter(url);
+
+        expect(style['background-image']).to.be.equal(`url(${ url })`);
+    });
+});

src/filters/srcset/srcset.spec.js

@@ -0,0 +1,34 @@
+import { expect } from 'chai';
+import srcsetFilter from './index';
+
+describe('srcset Filter', () => {
+    it('srcset with one image', () => {
+        const urls = [
+            'http://via.placeholder.com/400x400',
+        ];
+        const srcset = srcsetFilter(urls);
+
+        expect(srcset).to.be.equal(``);
+    });
+
+    it('srcset with two images', () => {
+        const urls = [
+            'http://via.placeholder.com/400x400',
+            'http://via.placeholder.com/800x800',
+        ];
+        const srcset = srcsetFilter(urls);
+
+        expect(srcset).to.be.equal(`${ urls[0] } 1x, ${ urls[1] } 2x`);
+    });
+
+    it('srcset with three images', () => {
+        const urls = [
+            'http://via.placeholder.com/400x400',
+            'http://via.placeholder.com/800x800',
+            'http://via.placeholder.com/1600x1600',
+        ];
+        const srcset = srcsetFilter(urls);
+
+        expect(srcset).to.be.equal(`${ urls[0] } 1x, ${ urls[1] } 2x, ${ urls[2] } 3x`);
+    });
+});