Ship Object - Walkthrough

Steps

• Discuss with your classmates what the domain model would look like for the above user story. Would recommend a pen and paper for this step.
• Create a new test file, which should describe your constructor.
• Create a new test spec (it) for ensuring an instance of your object can be created.
• Write the code that makes this test pass.
• Create another test spec for each property and/or method you identify.
• Write the code that makes this test pass.
• Add, commit with a meaningful message, and push to GitHub.

Domain Model

From the user story:

As a cruise ship captain,
So I can get passengers aboard a ship,
I want a ship to have a starting port.

The domain model for this user story might look like this:

describe Ship

We have a Ship object so we'll describe a Ship constructor.

Create a __tests__ folder in your project root, and inside create a new file Ship.test.js.

First, we'll import in our constructor file. It doesn't exist yet, but we're developing using a test-driven approach, so that's okay:

:exclamation: The /* globals describe it expect */ just tells VS Code and the linter that these variables don't exist in the scope (because the jest test runner brings them into scope), so don't show linter errors for them.

Then below, we'll describe our constructor:

Save the file, and in your Terminal run npm run test. You should fail with the following:

The error here is: Cannot find module '../src/Ship.js' from 'Ship.test.js'. We can solve this by creating the Ship.js file in a new folder in the project root: src/. Run your tests again. You should now fail with:

Test an instance of Ship can be created

To fix this error, we can proceed to write our first test:

Run your tests:

Write the code to make this pass

:exclamation: You should be able to do this without the walkthrough. Once you've passed the test, then proceed.

it has a startingPort

We identified a property of startingPort during the domain modelling, so write a test to check a Ship has this property:

Run your tests. They should fail with:

  ● Ship › has a starting port
    expect(received).toBe(expected) // Object.is equality
    Expected: "Dover"
    Received: undefined
    Difference:
      Comparing two different types of values. Expected string but received undefined.
      10 |     const ship = new Ship('Dover');
      11 |
    > 12 |     expect(ship.startingPort).toBe('Dover');
         |                               ^
      13 |   });
      14 | });
      15 |
      at Object.it (__tests__/Ship.test.js:12:31)

Write the code to make this pass

:exclamation: You should be able to do this without the walkthrough. Once you've passed the test, then proceed.

Add, commit with a meaningful message, and push to GitHub.

git add __tests__/Ship.test.js
git add src/Ship.js
git commit -m "Tests for Ship and Ship constructor"
git push origin main