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Testing with f#

By : Mikael Lundin

3.7 (3)

Testing with f#

3.7 (3)

By: Mikael Lundin

Overview of this book

If you are a developer who wants to test applications using F#, this is the book for you. Basic experience of testing and intermediate experience of functional programming in F# is expected.

Preface

Preface

What this book covers

What you need for this book

Who this book is for

Conventions

Reader feedback

Customer support

Free Chapter

1. The Practice of Test Automation

1. The Practice of Test Automation

Testing as a practice

Building trust

The purpose of testing

Testing with intent

Writing tests for regression

Summary

2. Writing Testable Code with Functional Programming

2. Writing Testable Code with Functional Programming

Purely functional

Immutability

Writing testable code

Expressiveness through functional programming

Summary

3. Setting Up Your Test Environment

3. Setting Up Your Test Environment

F# Interactive

Testing with Visual Studio

Comparing MSTest, NUnit, and xUnit

Tools and frameworks

Executing a test suite outside Visual Studio

FAKE

Continuous integration

Summary

4. Unit Testing

4. Unit Testing

Structuring your tests

Arrange, act, assert

FsUnit

Unquote

Testing in isolation

Finding the abstraction level

Test doubles

Dependency injection

Stubbing with Foq

Mocking

Dealing with databases

Summary

5. Integration Testing

5. Integration Testing

Good integration tests

Your first integration test

Setting up and tearing down databases

Speeding up integration testing

Testing stored procedures

Data-driven testing

Testing web services

Summary

6. Functional Testing

6. Functional Testing

Specifications

Setting up TickSpec

Web-browser-based testing

Regression testing

Summary

7. The Controversy of Test Automation

7. The Controversy of Test Automation

Bugs or defects

The cost of quality

The false security of code coverage

Test-driven development

Testing or fact-checking

Summary

8. Testing in an Agile Context

8. Testing in an Agile Context

Building a bridge or tending to a garden

The broken iron triangle

Visualizing metrics

The Kanban board

Predictability

Testing in agile

Summary

9. Test Smells

9. Test Smells

Tests that break upon refactoring

Tests that break occasionally

Tests that never break

Tests that are too complex

Tests that require excessive setup

Developers not writing tests

Summary

10. The Ten Commandments of Test Automation

10. The Ten Commandments of Test Automation

Testing behavior, not implementation

Using ubiquitous language in your test name

Asserting only one thing in your test

Don't mock the Mockingbird

Always refactor your SUT

Your test should never be more than 10 lines of code

Always test in isolation

Controlling your dependencies

Your test is a ninja

The test is not complex

Summary

Index

Index

Test doubles

The definition of a test double is a dependency you inject into your program, instead of ordinary functionality, in order to isolate the thing you want to test. We've already seen what you can do by making in-memory versions of your dependencies built in. Sometimes, we want our tests to be able to inject a specific tests dependency that is not built in, and this is where the SUT needs to be extensible enough to allow it.

Just as in C#, we use an interface or abstract class to enable extensibility and allow for dependency injection. To enable this, F# provides us with the ability to implement interfaces using object expressions. This is a great feature for testing.

As an example, lets start with defining an interface. This interface will open a Comma Separated Value (CSV) file and allow reading it line by line, as shown in the following code:

// loading and processing a csv file line by line
type ICsvReader =
    // open file and return sequence of values per line
    abstract...

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