wrote several tests for checkbox; made some small edits in component

.storybook/__storyshots__/CheckBox.shot

+exports[`basic usage`] = `
+<label>
+  <input
+    aria-checked={false}
+    aria-describedby="checkbox"
+    defaultChecked={false}
+    disabled={undefined}
+    name="checkbox"
+    onClick={[Function]}
+    tabIndex="0"
+    type="checkbox" />
+  check me out!
+</label>
+`;
+
+exports[`call a function`] = `
+<label>
+  <input
+    aria-checked={false}
+    aria-describedby="checkbox"
+    defaultChecked={false}
+    disabled={undefined}
+    name="checkbox"
+    onClick={[Function]}
+    tabIndex="0"
+    type="checkbox" />
+  check out the console
+</label>
+`;
+
+exports[`default checked`] = `
+<label>
+  <input
+    aria-checked={true}
+    aria-describedby="checkbox"
+    defaultChecked={true}
+    disabled={undefined}
+    name="checkbox"
+    onClick={[Function]}
+    tabIndex="0"
+    type="checkbox" />
+  (un)check me out
+</label>
+`;
+
+exports[`disabled`] = `
+<label>
+  <input
+    aria-checked={false}
+    aria-describedby="checkbox"
+    defaultChecked={false}
+    disabled="true"
+    name="checkbox"
+    onClick={[Function]}
+    tabIndex="0"
+    type="checkbox" />
+  you cannot check me out
+</label>
+`;

__tests__/checkbox-test.jsx

 import React from 'react';
-import { shallow } from 'enzyme';
+import { shallow, mount } from 'enzyme';
 import CheckBox from '../src/CheckBox';
 
 describe('<CheckBox />', () => {
+  it('attributes are set correctly', () => {
+    const wrapper = shallow(
+      <CheckBox
+        name="checkbox"
+        describedBy="this is a checkbox"
+        label="check me out!"
+        checked="false"
+      />
+    )
+
+    expect(wrapper.find('[name="checkbox"]').exists()).toEqual(true);
+    expect(wrapper.find('[type="checkbox"]').exists()).toEqual(true);
+    expect(wrapper.find('[defaultChecked=false]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-describedby="this is a checkbox"]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-checked=false]').exists()).toEqual(true);
+    expect(wrapper.find('[tabIndex="0"]').exists()).toEqual(true);
+  });
+
   it('aria-label changes after click', () => {
     const wrapper = shallow(
       <CheckBox
@@ -14,8 +32,67 @@ describe('<CheckBox />', () => {
       );
 
     expect(wrapper.find('[aria-checked=false]').exists()).toEqual(true);
+
     wrapper.find('input').simulate('click');
     expect(wrapper.find('[aria-checked=false]').exists()).toEqual(false);
     expect(wrapper.find('[aria-checked=true]').exists()).toEqual(true);
+
+    wrapper.find('input').simulate('click');
+    expect(wrapper.find('[aria-checked=false]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-checked=true]').exists()).toEqual(false);
+  });
+
+  it('check that callback function is triggered when clicked', ()=> {
+    const wrapper = shallow(
+      <CheckBox
+        name="checkbox"
+        descibedBy="checkbox"
+        label="check me out!"
+        checked="false"
+        onChange={() => console.log('the checkbox changed state')}
+      />,
+    );
+    const spy = jest.spyOn(wrapper.instance(), 'onChange');
+
+    expect(spy).toHaveBeenCalledTimes(0);
+    wrapper.find('input').simulate('click');
+    expect(spy).toHaveBeenCalledTimes(1);
+  });
+
+  it('checks if start state can be set to checked', () => {
+    const wrapper = shallow(
+      <CheckBox
+        name="checkbox"
+        describedBy="checkbox"
+        label="I start checked"
+        checked="true"
+      />,
+    );
+
+    expect(wrapper.find('[defaultChecked=true]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-checked=true]').exists()).toEqual(true);
+
+    wrapper.find('input').simulate('click');
+    expect(wrapper.find('[defaultChecked=false]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-checked=false]').exists()).toEqual(true);
+  });
+
+  it('checkbox can be disabled', () => {
+    const wrapper = mount(
+      <CheckBox
+        name="checkbox"
+        describedBy="checkbox"
+        label="I am disabled"
+        checked="false"
+        disabled={true}
+      />,
+    );
+
+    expect(wrapper.find('[defaultChecked=false]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-checked=false]').exists()).toEqual(true);
+
+    wrapper.find('input').simulate('click');
+    expect(wrapper.find('[defaultChecked=false]').exists()).toEqual(true);
+    expect(wrapper.find('[aria-checked=false]').exists()).toEqual(true);
   });
 });

src/CheckBox.jsx

@@ -8,6 +8,10 @@ class CheckBox extends React.Component {
     super(props);
 
     this.handleClick = this.handleClick.bind(this);
+    if (this.props.onChange) {
+      this.onChange = this.props.onChange.bind(this);
+    }
+
     if (props.checked === 'true') {
       this.state = {
         checked: true,
@@ -29,8 +33,8 @@ class CheckBox extends React.Component {
         checked: true,
       });
     }
-    if (this.props.onChange) {
-      this.props.onChange();
+    if(this.onChange) {
+      this.onChange();
     }
   }
 
@@ -39,12 +43,12 @@ class CheckBox extends React.Component {
     const props = { ...this.props };
 
     return (
-      <label htmlFor={props.checkLabel}>
+      <label>
         <input
           name={props.name}
           type="checkbox"
           defaultChecked={this.state.checked}
-          aria-describedby={props.describedby}
+          aria-describedby={props.describedBy}
           aria-checked={this.state.checked}
           tabIndex="0"
           onClick={this.handleClick}