Prog272 Midterm 2017

This documents contains a description of what I want to see on the midterm. We want to keep moving to the point where we can take a JSON file containing addresses, and display, iterate and edit them in a React based program. The output from the components you create should be thoroughly tested.

In git-convert, we learned to map the JSON we download with curl from a webservice. For extra credit, automatically transform that JSON into a set of data that we can easily consume in our application.


I want you to polish and extend the CongressAddress program that we have been working on for the last several weeks. Below I list the key features that I’m looking for in your assignment.

  • Display at least three views created with React components:
    • AddressShow
    • AddressEdit
    • SmallNumbers
      • Show at least five numbers, but you can update them with a single button click.
    • Each React component should be in its own file. The file names should begin with a capital letter and use Pascal casing.
  • Menu
    • Make sure you are styling it.
    • I picked the first of the Horizontal Navigation Bar Examples
    • Replace the default “Atom” logo.svg image file with one of your own choosing.
  • You should be able to iterate back and forth over at least 5 addresses
    • Extra credit button go to first and last
    • Be able to edit any of the address
    • Changes should remain through the session
    • Full credit comes if you can display the full list of addresses from our GetAddress web-service project.
  • Testing
    • You should have at least 5 test files:
    • Address.test.js, AddressEdit.test.js, AddressShow.test.js
    • ElfHeader.test.js and SmallNumbers.test.js
    • I’m expecting at least 30 tests, but full credit comes when you write more than 50 tests.
  • Refactoring
    • Make sure you have the following folders with appropriate content:
    • src/__tests__
    • src/components
    • src/css
    • src/images


To help write your tests, you should use ElfDebugEnzyme. I’m expecting to see evidence of its use in your code. You can find ElfDebugEnzyme here:

Here is an example of how to use it:

  import ElfDebugEnzyme from '../ElfDebugEnzyme';
  const elfDebug = new ElfDebugEnzyme(true);

  elfDebug.getIndex(wrapper, '.AddressShowDiv', 0);


I want you to be able to check the formating of your code with JSCS when I open it in WebStorm. If you have not done so already, install JSCS globally:

npm install -g jscs

Make sure JSCS is turned on in WebStorm. Go to **Settings Languages and Frameworks JavaScript Code Quality Tools JSCS** and make sure it is enabled.

Put this .jscsrc file in the root of your projects. Probably one for client and one for server:

    "preset": "google",
    "maximumLineLength": null,
    "validateIndentation": 4,
    "excludeFiles": [
Go to **Setting Editor Code Style JavaScript. On the Settings tab, in the first section, called **Before Parentheses, set In Function Expression to false (unchecked). This means there should be no space after the word function.. Our code should look like this: function() {}. Not like this function () {}. Note the space after the word function in the second example.
JSCS should pass for your files. You can probably make this happen by choosing **Code Reformat** in WebStorm, or by running the NPM package called js-beautify, which should be installed on your system in the global ~/npm/bin directory. If it is not installed, install it. But I do most of my formatting with WebStorm not js-beautify.

Hopefully works for you too

JSCS Punctuator

Many of us have been getting errors or warnings about punctuators. This can be fixed, but there are a couple steps invovled. Here is our current onAddressChange method:

onAddressChange = (event) => {
    this.addressIndex += 1;
    const address = addresses[this.addressIndex];

        address: address

Get rid of the arrow function syntax, which is lovely cutting edge experimental code that JSCS is not handling correctly:

onAddressChange(event) {
    this.addressIndex += 1;
    const address = addresses[this.addressIndex];

        address: address

All this is good and well, but now the this variable in onAddressChange is no longer valid. To fix it, add this code to the constructor:

this.onAddressChange = this.onAddressChange.bind(this);

The call to bind shown above is the traditional way to solve this problem. I was enamored of the arrow function syntax and thought it a better way to solve the “invalid this” problem. But that solution is not certain to make it into the final ES6 spec. So I’m opting for this alternative solution, even if we lose the arrow function syntax.

See the setQuiet method in this gist for a complete working example of the fix:

NOTE: When I got the punctuator error, the editor did not usually point right at the source of the problem. Instead, for me, it was often pointing at the first import statement at the top of the file. Eventually, I realized the problem was not the import statement, but the arrow functions. I found this to be quite confusing, and it took me several tries before I sorted it out. Once I removed the arrow function, however, the other JSCS errors were easier to find, and WebStorm pointed me at the place in the file where the error occurred.

Turn it in

Git add, commit and push. Git tag and/or create a branch. (If you are doing both, add the tag after you create the branch.) Use the word Midterm in your tag and/or branch messages. If there is any doubt as to which folder and branch your midterm is in, be sure to spell it out. For instance:

  • Branch: midterm
  • Tag: v6.00 with a message for midterm
  • Folder: CongressAddress

I’m happy if your branch is master, but if you feel comfortable creating a midterm branch, then do so just before you submit the assignment. You can update the branch at any time until the actual due date for the assignment. Even then, I would probably prefer a late update to a broken program.

Shallow Button Clicks

By definition, enzyme shallow works with only one component at a time. When we use shallow, it is therefore not possible to check if a button click is working correctly since that involves the interaction of two components.

However, even when we use shallow, an onClick function can be created within a button test to validate that the button responds to clicks. We implement the onClick function as a callback, and then confirm that when we click the button the callback is executed.

Here is an example:

// button test
it('responds to a button click', () => {
    //create variable to track button click status
    let clicked = false;
    //create function to assign as onClick
    const callback = () => {
        clicked = true;

    const wrapper = shallow(<AddressShow onSetAddress = {callback} address={address}/>);


Thanks to Andrew Wilson for inspiring this tip!

Contains Matching Element

Remember that for tests on our input elements we need to use containsMatching element:

contains insists that all attributes for a tag match exactly, while containsMatchingElement allows you to match just one out of multiple attributes. In other words, it ignores attributes you don’t care about. We have to use containsMatchingElement when testing our input controls since they contain onChange functions, and it is not easy or perhaps not even possible to match a function:

const inputElement = <input value='Robin Dudette'/>;
// Code omitted

This works even if the input control has a number of other attributes other than value.

Don’t Use Fetch on Midterm

Unless you are absolutely sure you know what you are doing, don’t call fetch on the midterm as it will break your tests. Just continue to get the data from address-list.js.

Filter Tests

Also, notice the menu the tests give you. Note the p option for filtering files. Suppose one of your test files is called Foo.test.js and one is called Bar.test.js. Press p and enter Foo. Only Foo.test.js will run:

Watch Usage
 › Press a to run all tests.
 › Press o to only run tests related to changed files.
 › Press p to filter by a filename regex pattern.
 › Press q to quit watch mode.
 › Press Enter to trigger a test run.

 pattern › Foo

The result might look like this:

 PASS src/__tests__/Foo.test.js
 React Foo Suite
 ✓ see if true is true (6ms)

Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 0.545s, estimated 1s
Ran all test suites matching "Foo".

Watch Usage
 › Press a to run all tests.
 › Press o to only run tests related to changed files.
 › Press p to filter by a filename regex pattern.
 › Press q to quit watch mode.
 › Press Enter to trigger a test run.

Even though I had several tests in my __tests__ folder, only the one that had Foo in its name was run.