Good example of using BDD language to write unit tests? - unit-testing

Question

I'm a big fan of BDD for integration tests and have started looking at using them from unit tests as well. From other questions (e.g. this one 1), I can see that people generally consider it acceptable to write BDD style unit tests. However, I haven't seen any examples of unit tests using BDD language. Seeing some concrete examples would help me get my head around it much better.
I'm wondering how to use BDD when the test is examining low level system behaviour that a user would not experience. For an integration/view test, I'd do something like this:
describe('Given that an author is using the question editor with a choice matrix question open ', function () {
describe('When the author clicks the 'Allow Multiple Responses' switch', function () {
it('Then the question preview should change from radio buttons to checkboxes', function () {
expect(....);
});
});
});
But what about if I'm testing the functionality of a low level method? Is it an anti-pattern if I'm trying to test a low level unit that a user would never touch it? For example, if I want to use Jasmine to test the functionality of a method called isCellShadedByAuthor(), my best guess is to do something like this:
describe("Given that the cell is in the response area not on the author side", function () {
it("When the cell is an author shaded cell, then isCellShadedByAuthor should return true", function () {
expect(isCellShadedByAuthor(1, 3)).toBeTruthy();
});
));
I guess another way to approach this situation is to try to elevate the test to a view test where I'd assert based on the presence of a CSS class rather than directly asserting on the return value of isCellShadedByAuthor(). This would reduce the coupling of the test to the implementation details.
For example, I could do ​
describe("Given that the cell is in the response area not on the author side", function () {
it("When the user hovers over an author shaded cell, then the cell should have the hover class", function () {
var cell = $('shading-cell[data-attribute-x="1"][data-attribute-y="1"]);
expect(cell.hasClass('hover-disabled')).toBeTruthy();
});
));

Answer 1

I'm not sure if you question pertains purely to JavaScript, but I have certainly used BDD unit tests for Java projects at previous employers. We made use of the BDDMockito class in the Mockito library.
We actually created a very simply BDD unit test template in our IDE that we all shared.
public void shouldDoFooOnBar() {
//given (perform setup here)
<code to define state of system>
//when
<single call to code under test>
//then
<code to assert expectations>
}
We found this gave our tests a nice consistent structure that was easy to read.
Here is a concrete example from Mockito:
public void shouldBuyBread() throws Exception {
//given
given(seller.askForBread()).willReturn(new Bread());
//when
Goods goods = shop.buyBread();
//then
assertThat(goods, containBread());
}
It is worth mentioning that we were also using BDD at the integration test level, but for this we were using FitNesse.