Say that I have two classes called Book
and Library
as follow:
var Book = function(title, author)
{
this.title = title;
this.author = author;
};
and
var Library = function()
{
var dbName = 'test';
this.getLibrary = function() {
return JSON.parse(window.localStorage.getItem(dbName));
};
this.save = function(library) {
window.localStorage.setItem(dbName, JSON.stringify(library));
};
}
Library.prototype.addBook = function(book) {
var library = this.getLibrary();
library.push(book);
this.save(library);
return library;
};
Library.prototype.removeBook = function(book) {
var library = this.getLibrary();
// Find and delete the right book
this.save(library);
return library;
};
My question is: How can I Unit testing the Library
class using QUnit to have a real atomic and independent test?
I wrote this test function but it has not satisfied me. It does not seem to be very atomic and independent since it mix several functions that I think should be tested independently. I'd like to know if there's a better way or I'm testing it good already.
test("test", function() {
var library = new Library();
deepEqual(library.getLibrary(), []);
// Add book1
var book1 = new Book("A book", "An author");
deepEqual(library.addBook(book1), [book1]);
deepEqual(library.getLibrary(), [book1]);
// Add book2
book2 = new Result("A new book", "Another author");
deepEqual(library.addBook(book2), [book2, book1]);
deepEqual(library.getLibrary(), [book2, book1]]);
// Remove book1
deepEqual(library.removeResult(book1), [book2]);
deepEqual(library.getLibrary(), [book2]);
// Remove book2
deepEqual(library.removeResult(book2), []);
deepEqual(library.getLibrary(), []);
});
Avoid writing "omnibus" tests that depend on internal state of the unit you're testing. Make fine-grained tests for specific behaviours , not state:
test("addBooksReturnsLibrary", function(){
var l = new Library();
l.addBook(new Book(...));
l.addBook(new Book(...));
var addBooksRetval = l.addBook(new Book(...));
deepEqual(addBooksRetval, l.getLibrary();
});
test("libraryContainsAddedBook"), function() {
var l = new Library();
var b = new Book(...);
l.addBook(b);
notEqual(-1, library.indexOf(b));
});
// etc and so forth
Heavy use of deepEqual
seems like it's a testing smell more often than not. If you do need, say, the books to be in the library in a specific order, I'd say it's better to test for those ordering constraints specifically.
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