What's Unit Testing

An unit test is a piece of code written by a developer that exercises a very
small, specific area of functionality of the code being tested.

  • An unit could be a module or more commonly a function or procedure, a class or an
  • interface.
  • White-box testing.
  • Each test case is independent from others.
  • Written by developer, not by QA engineer.
  • Released into code repository.
  • Ideally all unit tests should pass before merging to repository.

Benefits

  • Dramatically decrease the number of defects in the code
  • Find problem early
  • Reduce the cost of change
  • Allow refactoring
  • A living documentation
  • Assist in develop code debugging

Limites

  • It will not catch following errors:
    • Integration errors
    • Broader system-level errors
    • Across multiple unites errors
    • Non-functional test, like performance
  • Not run in real deployment environment
  • Usually more test code than real code
  • Sometimes difficult to test, like multi-thread

RackHD Unit Testing Code Architecture

  • All unit testing code in “spec” folder
  • “spec” folder has same structure with source
  • Unit testing file must be end with “-spec”
  • Unit testing file and the target file has same file name except “-spec” suffix.
  • spec/helper.js wraps all common functions/objects that shared by all unit-testing.

Run Unit Testing

Unit Testing Technical Stack

  • Test framework: Mocha
  • Test style: BDD
  • Assertion library: Chai
  • Spy/Mock library: Sinon
  • HTTP test library: supertest/nock
  • Private function test: rewire
  • Test coverage: istanbul/coveralls
  • Unit test CI: TravisCI/Jenkins

Typical Unit Testing Example

spec/helper.js

Dependency Injection in Unit Testing

  • Modules injection

    • helper.js has helped to inject all on-core modules
    • the helper.js in on-http has helped to injecto all api related modules
    • other modules need you inject it manually

  • Replace the whole of a di module

var waterline = {};
helper.setupInjector([
    helper.di.simpleWrapper(waterline, 'Services.Waterline');
]);

//Then feel free to add function for any function for the mocked objects
waterline.nodes = {
    updateByIdentifier: sinon.stub().resolves(),
    needByIdentifier: sinon.stub().resolves()
};
  • spy a function of di module.
var progressService = helper.injector.get('Services.GraphProgress');
sinon.spy(progressService, 'publishTaskProgress');

Unit Testing Coverage

function max(x, y) {
    return x > y ? x : y;
}

max(1, 2);
  • branch coverage
function max(x, y) {
    return x > y ? x : y;
}

max(1, 2)
max(2, 1)
  • path coverage
function max(a, b, c, d) {
    let x = a > b ? a : b;
    let y = c > d ? c : d;
    return x > y ? x : y
}

max(1, 2, 3, 4);
max(4, 3, 2, 1);

Misc

  • Random testing order
  • timeout control
  • Which level to inject stub

Introduce the framework and tool sets of RackHD unit-testing.

Goals:

(1)Understand the mocha framework.

(2)Understand the usual libraries: chai, sinon, supertest

(3)Understand how to run the unit-test.

(4)Understand how to measure the test coverage.

(5)Understand how to unit-test a Promise

(6)Understand how to handle di in unit-test.

(7)Understand the best practice of unit-test.

(8)Understand the common mistakes and avoid it.

Practice:

(1)Find a source file that doesn’t have the unit-test, then replenish it.

Extends:

(1)Read the source code chai, sinon.

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