Testing Involving Database - node.js

Question

well before specifying my problem, i want to tell that i'm new to the field of testing, so here is my problem:
i developed a rest api using express + sequelize(mysql), and i want to write some test for my api. i choosed to use jasmine library for testing.
so right know i want to test the create and update rest endpoint, i will need access to a database, but the problem is that the test cases are run in parallel, and there is only one database, so if i want to delete all item from a table in a test case, and another test case have create a row in that table, there will be a problem.
const request = require('superagent');
const models = require('../../src/models');
const Station = models.Station;
describe("station testing", function () {
before(() => {
// delete and recreate all database table
// before running any test
});
describe("crud station", function () {
it('should create model', () => {
Station.create({
'name': 'test',
lat: 12,
long: 123,
}).then( model => {
expect(model).toBeTruthy();
});
});
it('should delete evrything', () => {
Station.deleteAll().then( () => {
// problem here if after the first model is created and before create model except is executed
expect(Station.Count()).toEqual(0);
}
});
});
});

Answer 1

Your problem is that you are not writing unit tests here.
You need to understand the most important rule of unit testing - only test one unit at a time. A unit can be thought of as an area of your code. In a traditional desktop project (Java, C#, etc), a unit would be one class. In the case of Javascript, a unit is harder to define, but it certainly will only include the Javacript. If you are including any server code (for example, the database) in your tests, then you are not unit testing, you are doing integration testing (which is also very important, but much harder).
Your Javascript will have dependencies (ie other code that it calls, say via Ajax calls), which in your case will include the server code that is called. In order to unit test, you need to make sure that you are only testing the Javascript, which means that when running the tests, you don't want the server code to be called at all. That way, you isolate any errors in that unit of code, and can be confident that any problems found are indeed in that unit. If you include other units, then it could be the other units that have the problem.
In a strongly-typed language (like Java, C#, etc), there are frameworks that allow you to set up a mock for each dependency. Whilst I haven't tried any myself (that's this week's job), there are mocking frameworks for Javascript, and you would probably need to use one of them to do real unit testing. You mock out the server code, so when you run the test, it doesn't actually hit the database at all. Apart from solving your problem, it avoids a whole load of other issues that you will likely hit at some point with your current approach.
If you don't want to use a mocking framework, one other way to do it is to change your Javascript so that the function you are testing takes an extra parameter, which is a function that does the actual server call. So, instead of...
deleteCustomer(42);
deleteCustomer(id) {
validate(id);
$.ajax(...);
}
...your code would look like this...
deleteCustomer(42, callServer);
deleteCustomer(id, serverCall) {
validate(id);
serverCall(id);
}
...where serverCall() contains the Ajax call.
Then, to unit test, you would test something like this...
deleteCustomer(42, function(){});
...so that instead of calling the server, nothing is actually done.
This is obviously going to require some rewriting of your code, which could be avoided by mocking, but would work. My advice would be to spend some time learning how to use a mocking framework. It will pay off in the long run.
Sorry this has been a bit long. Unfortunately, you're getting into a complex area of unit testing, and it's important to understand what you're doing. I strongly recommend you read up about unit testing before you go any further, as a good understanding of the basics will save you a lot of trouble later on. Anything by Robert Martin (aka Uncle Bob) on the subject will be good, but there are plenty of resources around the web.
Hope this helps. If you want any more info, or clarification, ask away.

Answer 2

Jasmine supports a function for beforeEach which run before each spec in a describe block.
You can use that.
describe("A spec using beforeEach and afterEach", function() {
var foo = 0;
beforeEach(function() { foo += 1; });
afterEach(function() { foo = 0; });
it("is just a function, so it can contain any code", function() {
expect(foo).toEqual(1);
});
it("can have more than one expectation", function() {
expect(foo).toEqual(1)
expect(true).toEqual(true);
});
});
So you could let the beforeEach take care of the delete operation.