An experimental TypeScript BDD framework.
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README.md

TypeSpec

A TypeScript BDD framework.

PM> Install-Package TypeSpec 

npm install typespec-bdd

The aim is to properly separate the business specifications from the code, but rather than code-generate (like Java or C# BDD tools), the tests will be loaded and executed on the fly without converting the text into an intermediate language or framework. This should allow tests to be written using any unit testing framework - or even without one.

Version 2.0.0

This version contains some breaking changes, although these are all improvements.

Please see the revised examples below, and in the example projects to see how to write steps using decorators.

Raise an issue or question if you get stuck.

Specifications

Specifications are plain text files, just like those used in other BDD frameworks. For example:

Feature: Basic Working Example
       In order to avoid silly mistakes
       As a math idiot
       I want to be told the sum of two numbers

@passing
Scenario: Basic Example with Calculator
       Given I am using a calculator
       And I have entered "50" into the calculator
       And I have entered "70" into the calculator
       When I press the total button
       Then the result should be "120" on the screen

Step Definitions

Step definitions are organised into classes, and the @given, @when, and @then decorators are used to mark the steps. You can also use the @step decorator if you want to re-use a step under multiple keywords.

You can use an interface to type your test context.

import { Assert, given, when, then } from './TypeSpec/TypeSpec';

export interface CalculatorTestContext {
	done: () => void; // Standard TypeSpec aync done method.
	calculator: Calculator;
}

export class CalculatorSteps {
	@given(/^I am using a calculator$/i)
	usingACalculator(context: CalculatorTestContext) {
		context.calculator = new Calculator();
	}

	@given(/^I have entered (\"\d+\") into the calculator$/i)
	passingArguments(context: CalculatorTestContext, num: number) {
		calculator.add(num);
	}

	@when(/^I press the total button$/gi)
	pressTotal() {
	}

	@then(/^the result should be (\"\d+\") on the screen$/i)
	resultShouldBe(context: CalculatorTestContext, expected: number) {
		const actual = context.calculator.getTotal();
		Assert.areIdentical(expected, actual);
	}
}

The available decorators are:

  • given
  • when
  • then
  • step

The decorator takes a regular expression, and an optional kind (so you can mark a step as async).

Async Steps

If the steps need to work with asynchronous code, you can mark them as asyn. When you do this, you'll need to inform the test context when you are done:

	@when(/^I press the total button$/gi, Kind.Async)
	pressTotal(context: CalculatorTestContext) {
	    window.setTimeout(() => {
			context.done();
		}, 500);
	}

Running Specifications

You can run any number of specifications by passing them to AutoRunner.run. Each specification will be loaded and parsed, with the appropriate steps being executed if they exist.

Important Note: because the TypeScript compiler will optimise your ECMAScript style import away if you don't use the dependency in your file, you should use the import style shown for CalculatorSteps for your step definition files.

import { AutoRunner } from './Scripts/TypeSpec/TypeSpec';

import './CalculatorSteps';

AutoRunner.run(
    '/Specifications/Basic.txt'
).then(() => {
    // The promises resolves after all specifications have run
	// including async steps.
});

Step Definitions

Steps are defined using a regular expression, and a function to handle the step. For example, the step for the condition Given I am using a calculator is defined below:

@given(/^I am using a calculator$/i)
myStep(context: CalculatorTestContext) {
    context.calculator = new Calculator();
}

This is a basic example, where the regular expression is just the static text to be matched, along with the i flag to allow case-insensitive matches.

You can use the decorators given, when, or then to add steps, which will limit where they are used, or you can use the step decorator to define a step that can be used in any case.

If you include variables in your condition, you can use the regular expression to match the step without the specific value. For example, the steps And I have entered "50" into the calculator and And I have entered "70" into the calculator both match the step defined below (but And I have entered "Bob" into the calculator will not match, because Bob does not match (\d+)):

@step(/^I have entered (\"\d+\") into the calculator$/i)
myStep(context: CalculatorTestContext, num: number) {
    context.calculator.add(num);
}

If you write a statement and no step definition can be found, TypeSpec will suggest a step method for you, including expressions for any arguments it finds. For example:

I have a step with a number "5" and a boolean "true" and a string "text"

Will result in the following suggested step definition:

@step(/^I have a step with a number (\"\d+\") and a boolean (\"true\"|\"false\") and a string "(.*)"$/i)
myStep(context: any, p0: number, p1: boolean, p2: string) {
    throw new Error('Not implemented.');
}

Regular Expressions

You can be as explicit as you like with the regular expressions. You don't have to allow case-insensitive matches (just remove the i in the examples above). You can use specific variable matching expressions such as the (\d+) matcher (decimal digits) in the examples - or you can use a very open matcher such as (.*) (any characters).

Regular expressions aren't as bad as they may appear, the short version is...

(\d+) - the \d matches digit characters, 0-9 and the + says there may be more than one, so keep going!

In Action:

This 17 word sentence shows that there are 2 matches to be found using this regular expression.

Almost all of your Regular Expressions should start /^ and end $/i. This tells the matcher to only match complete sentences. Without these you may match partial conditions, causing accidental matching of steps where the language is similar, for example:

  • When the switch is turned on
  • When the automatic switch analyzer says the switch is turned on

The long version is available at MDN Regular Expressions.

Common TypeSpec Condition Strings

To find "1" here.

To find (\"\d+\") here.

To find "a string" here.

To find "(.*)" here.

To find "true" here.

To find (\"true\"|\"false\") here.

Grouping Steps

You should use a class to wrap related step definitions. However, don't fall into the trap of storing state on the class; use the context variable that is passed to the step by TypeSpec - as this will keep state between steps in different classes, and no matter what the current scope of this is.

The context variable is completely dynamic, but you can use an interface to give it more clarity in your step definitions.

Composition

The composition of the test is shown below.

import { AutoRunner } from './Scripts/TypeSpec/TypeSpec';

import './CalculatorSteps';

AutoRunner.run(
    '/Specifications/Basic.txt',
    '/Specifications/MultipleScenarios.txt',
    '/Specifications/ScenarioOutlines.txt'
);

You pass the list of specifications into the run method. Each specification is loaded, parsed, and executed.

The run method returns a promise, should you need to execute code after the test. This allows you to run code after all specifications have run, including where there are async steps.

Excluding Specifications

You can exclude specifications by tag, by passing the tags to exclude to the SpecRunner before calling runner.run(...:

import { AutoRunner } from './Scripts/TypeSpec/TypeSpec';

AutoRunner.excludeTags('@exclude', '@failing');

The @ is optional here, you could exclude using failing or @failing - both will work.

Test Reporting

By default, test output is sent to the console. You can override this behaviour by supplying a custom test reporter that extends the TestReporter class:

import { TestReporter } from './TypeSpec/TypeSpec';

export class CustomTestReporter extends TestReporter {
	//...
}

There are two built-in test reporters available:

  • TapReporter - produces TAP compliant output
  • TestReporter - outputs results to the console

There is also an HTML test reporter in the TypeSpec sample project.

You tell the AutoRunner which reporter to use:

AutoRunner.testReporter = new CustomTestReporter();

Test Hooks

There are a number of test hooks available that you can use to run code at various points during a test run.

interface ITestHooks {
	beforeTestRun(): void;
	beforeFeature(): void;
	beforeScenario(): void;
	beforeCondition(): void;

	afterCondition(): void;
	afterScenario(): void;
	afterFeature(): void;
	afterTestRun(): void;
}

You can set your test hooks on the AutoRunner.

AutoRunner.testHooks = new CustomTestHooks();

Scenario Outlines

Scenario outlines allow you to specify the example data in a table:

Feature: Scenario Outline
       In order to make features less verbose
       As a BDD enthusiast
       I want to use scenario outlines with tables of examples

@passing
Scenario Outline: Basic Example with Calculator
       Given I am using a calculator
       And I have entered "<Number 1>" into the calculator
       And I have entered "<Number 2>" into the calculator
       When I press the total button
       Then the result should be "<Total>" on the screen

Examples:
    | Number 1 | Number 2 | Total |
    | 1        | 1        | 2     |
    | 1        | 2        | 3     |
    | 2        | 3        | 5     |
    | 8        | 3        | 11    |
    | 9        | 8        | 17    |

TypeScript / C# Comparison

If you are familiar with BDD in C# or Java, this comparison may be useful when considering the difference between TypeSpec and tools such as SpecFlow or Cucumber.

TypeScript:

@given(/^I have entered (\d+) into the calculator$/i)
enterNumber(context: any, num: number) {
    calculator.add(num);
}

C#

[Given("I have entered (\d+) into the calculator")]
public void EnterNumber(decimal num) {
    calculator.Add(num);
}

Key differences:

  • You should always use the ^ start of string expression and the $ end of string expression in TypeSpec (although you are not forced too)
  • You can choose whether the step matcher is case sensitive (pass the i flag to ignore case)
  • The first argument passed to a step is always the test context