testing_with_jasmine.md

#JavaScript Testing With Jasmine Most software developers know that they should be writing tests for their code. However, more often than not they won't because it means learning yet another concept. In this piece, I will walk you through testing your JavaScript with Jasmine.

Jasmine is an open source testing framework for JavaScript which aims to run on any JavaScript-enabled platform. It is heavilly influenced by other testing frameworks, such as ScrewUnit, JSpec, and RSpec.

##Behavior Driven Development Before I dive into BDD, let's understand some fundamentals about testing.

Test Driven Development

TDD is the process of writing and running your test. Following TDD makes it possible to have a high test coverage, or the percentage of code that is tested; the higher the coverage, the better. Additionally, TDD reduces the likelihood of having bugs in your tests, which can otherwise be difficult to track down.

The process consists of the following steps:

1. Start by writing a test.
2. Run the test and watch it fail. If the test does not fail, then you know you have a bug in your test.
3. Write a minimal amount of code required to make the test pass.
4. Run the test to check the new test passes.
5. Refactor your code.
6. Repeat

Now that you understand the process of TDD, let's move on to BDD.

BDD is a bit more complex because it typically requires a team of developers, rather than a single developer, to practice it fully. Here are a few BDD practices:

• Establishing goals of different stakeholders required for an idea to be implemented, and involving stakeholders in this implementation through outside-in software development.

• Using examples to describe the behavior of different units of code

• Automating said examples to provide rapid feedback and regression testing.

Before I plunge into Jasmine, let's understand some basic testing terminology:

Unit testing- Low level tests to check functionality of classes, methods, or functions. This is what I will be focusing on. Unit tests run fast.

Acceptance/Feature tests- High level tests conducted to make sure all requirements are met. Acceptance tests run slow.

Integration/function/service-level testing- Testing between unit and acceptance tests. In most cases this will involve testing RESTful APIs.

##Installing Jasmine First, we will need to install the jasmine gem.

$ npm install -g jasmine

Second, to make sure it works, create a directory called, jasmine_testing, then type:

$ jasmine init

This will generate the following path in our jasmine_testing directory:

spec/support/jasmine.json

This file informs Jasmine where to find the tests and any helper files.

Now that we've set up Jasmine, let's learn the syntax and write our first test.

##Learning the syntax

Jasmine tests are primarily made up of two parts: describe blocks and it blocks. Let's take a look at how they work.

describe("fahrenheit_to_celsius_test",function(){
  it("converts 100 fahrenheit to 			
  	celsius",function(){
	// Setup
    var fahrenheit = 100;
	var result = fahrenheit_to_celsius(fahrenheit);
    // Checking the result
	expect(result).toBeCloseTo(37.778,3);
  });
});

Both describe and it are functions that take two parameters: a text string and a function. The idea is to make the text string as humanly readable as possible. Notice that both the describe and the it block form sort of a sentence which gives the developer an idea of what that block tests.

Think of the describe block as a general container and the it block as a place where you can set up the code necessary to for your test. Once your it block is setup, you'll continue by writing the expect function. In this function you will pass in whatever code you are testing. Notice how in my example I expect the result from the fahrenheit_to_celsius function to return a close to 37.778.

In your jasmine_testing directory, run the test and watch it fail. i.e.

$ jasmine

Next we will need to write the appropriate code to pass said test. Create an app directory for your script. Inside of it create and write your script there. The boiler plate should look something like this:

fahrenheit_to_celsius(fahrenheit){
	// take the fahrenheit and convert it to celsius
}

Run your test again in the jasmine_testing directory and watch it pass.

##Conclusion There is tons more you can do with Jasmine which I did not describe in the tutorial. I highly recommend you check out the Jasmine website and GitHub.

In conclusion, if you are not testing your JavaScript code, start now! It is an underrated practice which will result in cleaner and less buggy code. Furthermore, Jasmine's fast and simple syntax makes testing simple. So take your development further by writing tests for your code.

Good hunting!