Reuse scenarios by using mocha

Question

Recently I've started to use JS and mocha.

I've wrote some tests already, but now I got to the point when I need to reuse my already written tests.

I've tired to look for "it" / "describe" reusing, but didn't find something useful...

Does anyone have some good example ?

Thanks

Answer 1

Considering that if you only do unit testing, you won't catch errors due to integration problems between your components, you have at some point to test your components together. It would be a shame to dump mocha to run these tests. So you may want to run with mocha a bunch of tests that follow the same general patter but differ in some small respects.

The way I've found around this problem is to create my test functions dynamically. It looks like this:

describe("foo", function () {
    function makeTest(paramA, paramB, ...) {
        return function () {
            // perform the test on the basis of paramA, paramB, ...
        };
    }

    it("test that foo does bar", makeTest("foo_bar.txt", "foo_bar_expected.txt", ...));
    it("test what when baz, then toto", makeTest("when_baz_toto.txt", "totoplex.txt", ...));
    [...]
});

You can see a real example here.

Note that there is nothing that forces you to have your makeTest function be in the describe scope. If you have a kind of test you think is general enough to be of use to others, you could put it in a module and require it.

Answer 2

Considering each test is only designed to test a single feature/unit, generally you want to avoid reusing your tests. It's best to keep each test self-contained an minimize the dependencies of the test.

That said, if you have something you repeat often in your tests, you can use a beforeEach to keep things more concise

describe("Something", function() {

  // declare your reusable var
  var something;

  // this gets called before each test
  beforeEach(function() {
    something = new Something();
  });

  // use the reusable var in each test
  it("should say hello", function() {
    var msg = something.hello();
    assert.equal(msg, "hello");
  });

  // use it again here...
  it("should say bye", function() {
    var msg = something.bye();
    assert.equal(msg, "bye");
  });

});

You can even use an async beforeEach

beforeEach(function(done) {
  something = new Something();

  // function that takes a while
  something.init(123, done);
});