What is BDD?
BDD (Behavior-Driven Design) is a way of working for software teams, which narrows the gap between business and technicians by:
- Encourage cross-role collaboration and build a common understanding of problem solving
- Work in fast, small iterations to increase feedback and value streams
- Generate system documents and automatically check system behavior
We do this by focusing on concrete, real-world examples that illustrate how we want the system to work. We use these examples to guide us from concept to implementation in the process of ongoing collaboration.
Gherkin syntax
The BDD feature (Feature) description uses Gherkin syntax. Gherkin uses a special set of keywords to provide structure and meaning to the executable specification. Each keyword is translated into multiple languages; in this reference we will use English.
Cucumber is a popular BDD testing framework that supports various platforms, and most lines in its documentation start with a keyword.
Comments are only allowed to appear at the beginning of a new line, i.e. anywhere in the feature file. They start with zero or more spaces, followed by a hash symbol (#) and some text. (Cucumber does not currently support block annotations.)
Spaces or tabs can be used for indentation. The recommended indentation level is two spaces. Here is an example:
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
Gherkin syntax can be used for referenceGherkin Reference - Cucumber Documentation
Configure the BDD test framework for TypeScript projects
Pass the commandyarn add -D @cucumber/cucumber chaiInstall the BDD test framework and Assert framework cai.
Create directory features, create files in the directory, the content is as follows:
# features/
Feature: Bank Account
Scenario: Stores money
Given A bank account with starting balance of $100
When $100 is deposited
Then The bank account balance should be $200
This document describes the deposit scenario. If you have US$100 in the bank deposit account and if you have US$100 in the deposit, the account should have US$200.
Create step-definitions\
const { Given, Then, When} = require( '@cucumber/cucumber');
const { assert } = require( 'chai');
let accountBalance = 0;
Given('A bank account with starting balance of ${int}', function(amount) {
accountBalance = amount;
});
When('${int} is deposited', function (amount) {
accountBalance = Number(accountBalance) + Number(amount);
});
Then('The bank account balance should be ${int}', function(expectedAmount) {
(accountBalance, expectedAmount);
});
We need to create the corresponding test code, which will be mapped through input and output verification in the type and feature file. The corresponding method of Given will obtain a mapping of the initial account amount of US$100 and pass it to accountBalance. In the corresponding method, the amount test will obtain an amount map of USD 100 deposited. Finally, in the corresponding method of Then, expectedAmount will be mapped to 200 US dollars, which is used to verify whether it is equal to accountBalance in the end. If the equality assertion returns normally, otherwise the BDD judges that the test Case fails.
We can pass the command
yarn cucumber-js features\**\*.feature -r step-definitions\**\*.js
Run the test.
To complete the automated configuration, you can create a file in the project root directory, with the following content:
//
let common = [
'features/**/*.feature', // Specify our feature files
'--require step-definitions/**/*.js', // Load step definitions
'--format progress-bar', // Load custom formatter
].join(' ');
= {
default: common
};
Execute the command againyarn cucumber-js, through the configuration items in the file, the feature file and step definition script file will be automatically found to complete the BDD test work.
refer to:
BDD Testing & Collaboration Tools for Teams | Cucumber
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