Posted August 22, 2023 by Rohith and Anusha ‐ 4 min read

In the world of software development, writing reliable and efficient tests is a crucial aspect of delivering high-quality code. ScalaTest, a popular testing framework for the Scala programming language, empowers developers to create expressive and maintainable tests that ensure the correctness of their code. In this blog, we'll dive deep into ScalaTest and explore its features, capabilities, and best practices for writing effective tests.

What is ScalaTest?

  • ScalaTest is an open-source testing framework designed specifically for the Scala programming language.

  • It provides a comprehensive set of tools for writing various types of tests, from unit tests to integration and acceptance tests.

  • ScalaTest encourages a behavior-driven development (BDD) approach, allowing developers to express their tests in a more human-readable and intuitive manner.

Key Features of ScalaTest


  • This style of testing is well-suited for writing small, isolated tests.

  • Each test is defined using the it keyword, making the code very readable.

  • It’s particularly useful for testing individual functions or methods.


  • FunSpec encourages a more structured testing approach by grouping related tests under descriptive contexts using the describe and it keywords.

  • This makes it easy to organize and understand the test suite, especially for larger projects.


  • If you prefer to write tests in a more sentence-like format, WordSpec is a great choice.

  • It’s designed to create tests that read like sentences, which can be especially useful for documenting the expected behavior of your code.


  • FeatureSpec is ideal for testing scenarios or features in an application.

  • It’s a BDD-style testing approach that lets you define tests in terms of features, scenarios, and steps, similar to how you’d describe the behavior of your application to someone else.


  • ScalaTest provides a wide range of matchers that allow you to specify expected behavior concisely.

  • For example, you can use matchers like shouldBe, shouldNotBe, shouldThrow, and more to define assertions in a human-readable format.

Mocking and Stubbing

  • ScalaTest integrates well with popular mocking libraries like Mockito and EasyMock.

  • This allows you to create mock objects and stub behavior for dependencies, enabling isolated testing.

Property-Based Testing

  • ScalaTest supports property-based testing using libraries like ScalaCheck.

  • Property-based testing generates test cases based on properties or invariants, uncovering edge cases that traditional example-based testing might miss.

Writing Tests with ScalaTest

Let’s walk through an example of writing tests using ScalaTest in a FlatSpec style:

import org.scalatest._

class CalculatorSpec extends FlatSpec with Matchers {
  "A Calculator" should "add two numbers correctly" in {
    val result = Calculator.add(2, 3)
    result should be (5)

  it should "subtract two numbers correctly" in {
    val result = Calculator.subtract(5, 3)
    result shouldEqual 2

  it should "throw an exception for division by zero" in {
    an [ArithmeticException] should be thrownBy {
      Calculator.divide(10, 0)
  • In this example, we’re testing a hypothetical Calculator class using the FlatSpec style.

  • We’re using various matchers like should, shouldEqual, and should be thrownBy to define our assertions.

Best Practices for ScalaTest

Descriptive Test Names

  • Use descriptive names for your tests.

  • Clear test names make it easier to understand the purpose of each test and help in debugging.

Keep Tests Independent

  • Ensure that your tests are isolated from each other.

  • Avoid sharing state between tests to prevent unexpected interactions.

Use Matchers Judiciously

  • Choose the appropriate matchers for your assertions.

  • Matchers like shouldBe and shouldEqual make your tests more readable and expressive.

  • When using styles like FunSpec or FeatureSpec, group related tests under descriptive contexts.

  • This improves the organization of your test suite.

Explore Matchers Documentation

  • ScalaTest offers a plethora of matchers.

  • Explore the official documentation to discover the full range of matchers available for various scenarios.

Regular Maintenance

  • As your codebase evolves, so should your tests.

  • Regularly update and maintain your tests to reflect changes in your application’s behavior.


  • ScalaTest is a powerful testing framework that empowers Scala developers to write reliable, expressive, and maintainable tests.

  • With its variety of testing styles, rich set of matchers, and integrations with other libraries, ScalaTest provides the tools you need to ensure the quality and correctness of your codebase.

  • By following best practices and exploring its features, you can effectively leverage ScalaTest to streamline your testing process and produce high-quality software.

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