Top Contract Testing Tools Every Developer Should Know in 2024

Microservices architecture has taken center stage in today's time, ensuring seamless communication between services is a critical imperative. 

By identifying integration issues early in the development cycle, contract testing helps prevent costly downstream failures and ensures the overall stability and reliability of your applications.

With a plethora of contract testing tools available, choosing the right one can be difficult. This blog post aims to simplify your decision-making process by highlighting the top contract testing tools that every developer should consider in 2024.

So, let's get started, but before that if you've any doubts on what all you can achieve with contract testing and all its know-hows, make sure to check out this blog:

What is Contract Testing?

In software development, complex systems are often built from interacting components. Contract testing establishes a well-defined interface, similar to an API, that governs communication between these components. This interface specifies the expected behavior of each component, including:

• Data formats: The structure and validation rules for data exchanged between components.

• Message specifications: The format and content of messages used for communication.

• Error handling: How errors and exceptions should be communicated and managed.

By defining and enforcing these contracts, contract testing ensures that components can interact seamlessly, regardless of their internal implementation details. This promotes:

• loose coupling, reduces integration complexity, and facilitates independent development and deployment of components.

  
  

What is consumer-driven contract testing?

Consumer-Driven Contract Testing is the widely accepted approach of performing contract testing.

Basically, there are two parties involved in a contract, one asking for the data(consumer) and the other one providing the data(provider).

Here, the consumer of the service dictates the terms of the contract. It tells the provider what it expects in terms of data format and structure. The provider then ensures that it can meet these expectations.

This approach has several benefits:

1. Flexibility:

   Consumers define their requirements, leading to more flexibility and less risk of miscommunication.
   

2. Independence:

   Teams can work independently on their services, as long as they adhere to the agreed contracts.
   

3. Reduced Risk of Breakdowns:

   By ensuring that the provider meets the consumer's expectations, the risk of breakdowns in communication between services is significantly reduced.

What are the Benefits of Contract Testing?

1. Problems are caught during development, not after deployment.
   

2. Teams can work on their services without constant coordination, as long as they adhere to the contracts.
   

3. Ensures that as long as the contract is respected, services will interact seamlessly in production.
   

4. Contract testing streamlines the integration and examination of microservices, making the process smoother.
   

5. The upkeep of the system is simplified and becomes less burdensome.
   

6. Contract testing allows for focused attention on individual modules. For instance, to assess module A's contract, there's no need for full integration with other modules; it can be evaluated on its own.

Contract Testing Use Cases

Contract testing stands out as an effective technique for verifying the dependability and interoperability of microservices and APIs. Nonetheless, it's important to note that it doesn't suit every testing need. Below, we outline several typical scenarios where contract testing is particularly beneficial:

Use Case 1: User Authentication in a Social Media App

➡️ Scenario:

In a social media application, there are two microservices: User Service and Post Service. The User Service handles user authentication, while the Post Service manages the creation and display of posts.

➡️ Contract:

The contract specifies that when the Post Service receives a user ID, it sends a request to the User Service to authenticate the user and receive basic user profile data.

Example Contract (JSON format):

{
  "request": {
    "path": "/authenticateUser",
    "method": "POST",
    "body": {
      "userId": "string"
    }
  },
  "response": {
    "status": 200,
    "body": {
      "userId": "string",
      "userName": "string",
      "isAuthenticated": "boolean"
    }
  }
}

➡️ Testing the Contract:

User Service: Tests to ensure it can process the authentication request and return user data in the correct format.

Post Service: Tests to verify it sends the correct user ID format and handles the received user data appropriately.

Understanding this use case, we can say that contract testing ensures that the microservices can reliably communicate with each other, adhering to the predefined contracts, which is vital for the smooth functioning of complex, distributed systems.

API Contract Testing Tools in 2024

API Contract Testing Tools are essential in modern software development, especially when dealing with microservices architectures. These tools help ensure that APIs behave as expected and adhere to their defined contracts.

We have covered both the free tools and the paid tools in the API Contract Testing category. The top 4 best performing API Contract Testing Tools to consider for 2024 are:

1. HyperTest

2. PACT

3. Spring Cloud Contract

4. Dredd

   
   

1. HyperTest - API Contract Testing Tool

HyperTest is a modern tool specifically designed for API contract testing. It offers robust capabilities for ensuring that APIs meet their specified contracts.

Key Features:

✔️Test GraphQL, gRPC & REST APIs

✔️Test Queues/Async flows and contracts for 3rd Party APIs

✔️Test message queues & autonomous database testing

✔️Automatic assertions on both data and schema

✔️Code Coverage Reports for both core functions as well as integration layer

✔️Integration with any CI/CD tool like Jenkins, Circle CI, GitLab etc

2. Pact - API Contract Testing Tool

Pact is a popular open-source tool for contract testing. It focuses on the interactions between consumer and provider by defining and verifying HTTP requests and responses.

Key Features:

✔️Consumer-Driven Contracts: Pact allows the consumer to define the expected behavior of the provider, which can then be verified by the provider.

✔️Mock Service: It provides a mock service for the consumer to interact with during testing, ensuring that the consumer's requests match the contract.

✔️Integration with CI/CD: Pact integrates seamlessly with continuous integration/continuous deployment pipelines, enhancing the development workflow.

✔️Language Support: Offers wide language support including Ruby, JVM languages (Java, Kotlin, Scala), NET, JavaScript, Swift, and more.

3. Spring Cloud Contract - API Contract Testing Tool

Designed for Spring applications, this tool is used for implementing Consumer-Driven Contract (CDC) testing.

Key Features:

✔️Integration with Spring: Perfect for applications built with the Spring framework.

✔️Stub Runner: Automatically generates stubs for the consumer, which can be used for tests.

✔️Supports Messaging: Apart from HTTP, it also supports contract testing for asynchronous messaging.

4. Dredd - API Contract Testing Tool

Dredd is a language-agnostic HTTP API testing tool that validates whether an API implementation adheres to its documentation.

Key Features:

✔️Support for API Blueprint and OpenAPI: Works with API Blueprint and OpenAPI specifications.

✔️Hooks: Offers hooks in several languages to set up preconditions or clean up after tests.

✔️Continuous Integration: Easy integration with CI tools and services.

Conclusion

Each of these tools has its strengths and fits different needs in the API development lifecycle. The choice of tool often depends on the specific requirements of the project, such as the programming language used, integration capabilities, and the complexity of the API interactions. By employing these tools effectively, teams can ensure more reliable and robust API communication within their applications.

Here is a detailed comparison chart of the most widely used contract testing tools, click here to get to know those tools more technically.

Check out our other contract testing resources for a smooth adoption of this highly agile and proactive practice in your development flow:

• Tailored Approach to Test Microservices

• Comparing Pact Contract Testing and Hypertest

• Checklist For Implementing Contract Testing