[Slide] Add test coverage for componentDidMount()

src/transitions/Slide.js

@@ -17,11 +17,10 @@ function getTranslateValue(props, element) {
     return `translate3d(${0 - (rect.left + rect.width)}px, 0, 0)`;
   } else if (direction === 'up') {
     return `translate3d(0, calc(100vh - ${rect.top}px), 0)`;
-  } else if (direction === 'down') {
-    return `translate3d(0, ${0 - (rect.top + rect.height)}px, 0)`;
   }
 
-  return 'translate3d(0, 0, 0)';
+  // direction === 'down'
+  return `translate3d(0, ${0 - (rect.top + rect.height)}px, 0)`;
 }
 
 export default class Slide extends Component {

src/transitions/Slide.spec.js

@@ -3,7 +3,8 @@
 import React from 'react';
 import { assert } from 'chai';
 import { spy } from 'sinon';
-import { createShallow } from 'src/test-utils';
+import ReactDOM from 'react-dom';
+import { createShallow, createMount } from 'src/test-utils';
 import Slide from './Slide';
 import transitions, { easing, duration } from '../styles/transitions';
 
@@ -181,4 +182,43 @@ describe('<Slide />', () => {
       });
     });
   });
+
+  describe('slidemount', () => {
+    let mount;
+    let mountWrapper;
+    let instance;
+
+    before(() => {
+      mount = createMount();
+      mountWrapper = mount(<Slide><div /></Slide>);
+    });
+
+    after(() => {
+      mount.cleanUp();
+    });
+
+    it('default value', () => {
+      mountWrapper.setProps({ in: false });
+      instance = mountWrapper.instance();
+      instance.componentDidMount();
+      const transitionElement = ReactDOM.findDOMNode(mountWrapper.instance().transition);
+      if (transitionElement instanceof window.HTMLElement) {
+        assert.strictEqual(transitionElement.style.transform, 'translate3d(0, 0px, 0)');
+      } else {
+        assert.fail('transition property of instance should be an HTMLElement');
+      }
+    });
+
+    it('non-default value', () => {
+      mountWrapper.setProps({ in: false, direction: 'right' });
+      instance = mountWrapper.instance();
+      instance.componentDidMount();
+      const transitionElement = ReactDOM.findDOMNode(mountWrapper.instance().transition);
+      if (transitionElement instanceof window.HTMLElement) {
+        assert.strictEqual(transitionElement.style.transform, 'translate3d(0px, 0, 0)');
+      } else {
+        assert.fail('transition property of instance should be an HTMLElement');
+      }
+    });
+  });
 });