summary.md

Summary - Part I: Test-Driven Development

Chapter 1: Automated Testing

1.1 The Unit Test

unit test ...

a piece of code that test a piece of production code.

characteristics:

• are stored on disk along with a version control system.
• should be easy and fast to run.
• should test software components in isolation.
• should also run isolated - no test should depend on another test
• should run simultaneously and in any order.

We run tests at any time ...

• when the implementation (feature) is complete, to verify its correct behavior.
• when the implementation changes, to verify its behavior is intact.
• when new units are added to the system, to verify it still fulfills its intended purpose.

xUnit ...

is a term to refer to test frameworks that are based on ideas and concepts or derive their structure on the Smalltalk's SUnit, designed by Kent Beck in 1988.

Exercise: have the strftime function to format %S seconds, %M minutes and %H hours.

1.2 Assertions

assertion ...

is a predicate that states the programmer's intended state of a system.

Colors for assertions

Red is used for "failure"

Green is used for "success"

1.3 Test Functions, Cases and Suites

test functions ...

are used to organize the tests to get a more fine-grained feedback

should exercise only one unit, but it may do so using one or more assertions

are required only to test one specific behavior of a single unit

test case ...

a set of related test functions/methods

test suites ...

test cases are usually organized in test suites in more complex systems

test suites > test cases > test functions

test fixtures ...

centralized setup of test data

are handled by the following methods:

• setUp aka before or beforeEach

• tearDown aka after or afterEach

1.4 Integration Tests

integration tests ...

test the sum of its parts (unit tests, two or more individual components)

1.5 Benefits of Unit Tests

importance of testing ...

writing tests is an investment

testing applications takes time

automated testing allows us to write a test once and run it as many times as we wish

regression testing ...

by "trapping" a bug in a test, our test suite will notify us if the bug ever makes a reappearance.

we can run all our tests prior to pushing code into production to make sure that past mistakes stay in the past.

refactoring ...

is vital to growing your application while preserving a good design.

you've done it by:

• Reusing code/methods. DRY (Don't Repeat Yourself)
• Renaming objects or functions

first step while refactoring:

“Build a solid set of tests for the section of code to be changed.” - Martin Fowler

without tests you have no reliable metric that can tell you whether or not the refactoring was successful, and that new bugs weren’t introduced:

“don’t touch anything that doesn’t have coverage. Otherwise, you’re not refactoring; you’re just changing shit.” - Hamlet D’Arcy

cross-browser testing ...

make use of a test runner to automate tests across multiple user agents aka browsers.

more benefits of well-written tests ...

serve as good documentation of the underlying interfaces.

new developers can get to know the system being developed better

1.6 Pitfalls of Unit Testing

pitfalls ...

writing tests is NOT always easy

in order to write truly great unit tests, the code you’re testing needs to be testable.