diff --git a/Libraries/StyleSheet/__tests__/flattenStyle-test.js b/Libraries/StyleSheet/__tests__/flattenStyle-test.js
index 6613944ed..2f0fdcc0f 100644
--- a/Libraries/StyleSheet/__tests__/flattenStyle-test.js
+++ b/Libraries/StyleSheet/__tests__/flattenStyle-test.js
@@ -8,30 +8,48 @@
  */
 'use strict';
 
-var flattenStyle = require('flattenStyle');
+const StyleSheet = require('StyleSheet');
+const StyleSheetValidation = require('StyleSheetValidation');
+const flattenStyle = require('flattenStyle');
+
+function getFixture() {
+  StyleSheetValidation.addValidStylePropTypes({
+    styleA: () => {},
+    styleB: () => {},
+  });
+
+  return StyleSheet.create({
+    elementA: {
+      styleA: 'moduleA/elementA/styleA',
+      styleB: 'moduleA/elementA/styleB',
+    },
+    elementB: {
+      styleB: 'moduleA/elementB/styleB',
+    },
+  });
+}
 
 describe('flattenStyle', () => {
-
   it('should merge style objects', () => {
-    var style1 = {width: 10};
-    var style2 = {height: 20};
-    var flatStyle = flattenStyle([style1, style2]);
+    const style1 = {width: 10};
+    const style2 = {height: 20};
+    const flatStyle = flattenStyle([style1, style2]);
     expect(flatStyle.width).toBe(10);
     expect(flatStyle.height).toBe(20);
   });
 
   it('should override style properties', () => {
-    var style1 = {backgroundColor: '#000', width: 10};
-    var style2 = {backgroundColor: '#023c69', width: null};
-    var flatStyle = flattenStyle([style1, style2]);
+    const style1 = {backgroundColor: '#000', width: 10};
+    const style2 = {backgroundColor: '#023c69', width: null};
+    const flatStyle = flattenStyle([style1, style2]);
     expect(flatStyle.backgroundColor).toBe('#023c69');
     expect(flatStyle.width).toBe(null);
   });
 
   it('should overwrite properties with `undefined`', () => {
-    var style1 = {backgroundColor: '#000'};
-    var style2 = {backgroundColor: undefined};
-    var flatStyle = flattenStyle([style1, style2]);
+    const style1 = {backgroundColor: '#000'};
+    const style2 = {backgroundColor: undefined};
+    const flatStyle = flattenStyle([style1, style2]);
     expect(flatStyle.backgroundColor).toBe(undefined);
   });
 
@@ -40,11 +58,99 @@ describe('flattenStyle', () => {
   });
 
   it('should recursively flatten arrays', () => {
-    var style1 = {width: 10};
-    var style2 = {height: 20};
-    var style3 = {width: 30};
-    var flatStyle = flattenStyle([null, [], [style1, style2], style3]);
+    const style1 = {width: 10};
+    const style2 = {height: 20};
+    const style3 = {width: 30};
+    const flatStyle = flattenStyle([null, [], [style1, style2], style3]);
     expect(flatStyle.width).toBe(30);
     expect(flatStyle.height).toBe(20);
   });
+
+  it('should not allocate an object when there is no style', () => {
+    const nullStyle = flattenStyle(null);
+    const nullStyleAgain = flattenStyle(null);
+
+    expect(nullStyle).toBe(nullStyleAgain);
+    expect(nullStyle).toBe(undefined);
+  });
+
+  it('should not allocate an object when there is a style', () => {
+    const style = {a: 'b'};
+    const nullStyle = flattenStyle(style);
+
+    expect(nullStyle).toBe(style);
+  });
+
+  it('should not allocate an object when there is a single class', () => {
+    const fixture = getFixture();
+    var singleStyle = flattenStyle(fixture.elementA);
+    var singleStyleAgain = flattenStyle(fixture.elementA);
+
+    expect(singleStyle).toBe(singleStyleAgain);
+    expect(singleStyle).toEqual({
+      styleA: 'moduleA/elementA/styleA',
+      styleB: 'moduleA/elementA/styleB',
+    });
+  });
+
+  it('should merge single class and style properly', () => {
+    const fixture = getFixture();
+    var style = {styleA: 'overrideA', styleC: 'overrideC'};
+    var arrayStyle = flattenStyle([fixture.elementA, style]);
+
+    expect(arrayStyle).toEqual({
+      styleA: 'overrideA',
+      styleB: 'moduleA/elementA/styleB',
+      styleC: 'overrideC',
+    });
+  });
+
+  it('should merge multiple classes', () => {
+    const fixture = getFixture();
+    var AthenB = flattenStyle([fixture.elementA, fixture.elementB]);
+    var BthenA = flattenStyle([fixture.elementB, fixture.elementA]);
+
+    expect(AthenB).toEqual({
+      styleA: 'moduleA/elementA/styleA',
+      styleB: 'moduleA/elementB/styleB',
+    });
+    expect(BthenA).toEqual({
+      styleA: 'moduleA/elementA/styleA',
+      styleB: 'moduleA/elementA/styleB',
+    });
+  });
+
+  it('should merge multiple classes with style', () => {
+    const fixture = getFixture();
+    var style = {styleA: 'overrideA'};
+    var AthenB = flattenStyle([fixture.elementA, fixture.elementB, style]);
+    var BthenA = flattenStyle([fixture.elementB, fixture.elementA, style]);
+
+    expect(AthenB).toEqual({
+      styleA: 'overrideA',
+      styleB: 'moduleA/elementB/styleB',
+    });
+    expect(BthenA).toEqual({
+      styleA: 'overrideA',
+      styleB: 'moduleA/elementA/styleB',
+    });
+  });
+
+  it('should flatten recursively', () => {
+    const fixture = getFixture();
+    var style = [{styleA: 'newA', styleB: 'newB'}, {styleA: 'newA2'}];
+    var AthenB = flattenStyle([fixture.elementA, fixture.elementB, style]);
+
+    expect(AthenB).toEqual({
+      styleA: 'newA2',
+      styleB: 'newB',
+    });
+  });
+
+  it('should ignore invalid class names', () => {
+    var invalid = flattenStyle(1234, null);
+
+    expect(invalid).toEqual({});
+    // Invalid class name 1234 skipping ...
+  });
 });