Writting tests

Behavioral uses Gherkin syntax to describe test execution. Here's example:

guess-the-word.feature

Feature: Guess the word

  # The first example has two steps
  Scenario: Maker starts a game
    When the Maker starts a game
    Then the Maker waits for a Breaker to join

  # The second example has three steps
  Scenario: Breaker joins a game
    Given the Maker has started a game with the word "silky"
    When the Breaker joins the Maker's game
    Then the Breaker must guess a word with 5 characters

This code is equivalent of the one below:

describe('Guess the word', () => {
  it('Maker starts a game', () => {
    // Here's step execution
  });

  it('Breaker joins a game', () => {
    // Here's step execution
  });
});

As we can see test is create for each scenario individually and group by the name of feature.

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Behavioral is responsible for converting Gherkin syntax into test runner of your choice (e.g. jest or karma).

Easy to read

In behavioral test description is decoupled from it's execution. One of the reason behind it is that tests with mixed description and execution mostly are very hard to read.

AAA pattern

In contrast to traditional JavaScript testing framework like jest, gherkin syntax is powered by AAA pattern, so each arrange, act and assert has his own description and each phase is clearly defined (given == arrange, when == act, then == assert).

describe('Guess the word', () => {
  test('Breaker joins a game', () => {
    // the Maker has started a game with the word "silky" - Arrange
    startAGame('silky');

    // the Breaker joins the Maker's game - Act
    breakerJoins();

    // the Breaker must guess a word with 5 characters - Assert
    expect(getBreakerResult()).toBeLessThanOrEqual(5);
  });
});

Sharing

Each step definition can be easly reused in other tests without additional effort of extracting it.

Tagging

Behavioral uses gherkin tags to add context to test execution. There is several ready to use built-in tags.

@skip

Setting it on feature level is equivalent of describe.skip (skipping whole file). When set on scenario level only tagged scenario is skipped.

@use()

Allows to pass execution context to tests. This tag requires path to the file containing execution context class.

# Use context from ./path/to/ExecutionContext exported as ExecutionContext
@bind(./path/to/ExecutionContext:ExecutionContext)
# Use context from ./path/to/ExecutionContext default export
@bind(./path/to/ExecutionContext)

It can be defined for feature or scenario. All context defined on feature level are inherited by scenarios.

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For full gherkin reference read Gherkin Reference

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Tagging​

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Tagging