Contract Tests with Spring Cloud Contract

Contract tests has a lot of significance and value in Micorservices world. You can keep fixing your end to end or integration tests, which runs very late in the build, are difficult to debug and cost lot of resources to maintain.

Component tests are good for testing integration between the various components of an API. However, in microservices world there are a number of APIs that serves different/unique purposes and are part of an application/system. Component tests alone can’t assure that integration between micorservices is working fine.

In case of Integration tests, testing  a change in one API can lead to horrible time consuming process of setting up all the APIs, databases, brokers etc. Using Docker instances and Docker compose for orchestration makes things a little easier, however, it comes with a cost of maintaining your docker images and docker-compose files.

Contract tests not only ensures that two APIs will behave nicely with each other, they also fail fast. Which means the moment a developer makes a change in an API (Producer) that can break other APIs (Consumers), the developer will get to know right there on his local setup. Consumer APIs will know for sure when they run the tests on any CI pipeline (Jenkins, CircleCI). 

Why I said that contract tests can do magic is because of couple of reasons:
  1. You don’t have to setup other microservices, brokers or database to test integration between micorservices. You can however, choose to use database for assertions in some cases, however no other services are required.
  2. A contract (not contract test), gets first executed on the Producer API, and ensures that the applications behaves the way contract says. Which means both the contract and code has to be in sync. In a way, some component tests are autogenerated which tests the API and ensures validness of input and output. You are getting code coverage as a byproduct.
  3. Finally, when you are writing component tests on the consumer side, you don’t need to mock the external APIs. You will get qualified stubs which represents the API. And these stubs are much more reliable that the mocks.



Overall, contract tests gives you a reliability of end to end tests and speed of Unit tests. Best of both worlds. 

Comments

Post a Comment

Popular posts from this blog

Spring Security - Adding more information to the authenticated user.

I was using spring Security to perform authentication against the database and I needed to load the user information once the user gets authenticated. However, the spring org.springframework.security.core.userdetails.User object was not allowing me add more details to the logged in User object. In my case, I had to add phone number to the authenticated user. In the following section I'll show as to how to add additional information to the authenticated user. Create an object to contain the additional information. We will first create a MediUser object which will extend the Spring org.springframework.security.core.userdetails.User object. The MediUser object contains additional information like first name, middle name, last name, phone number and alternative phone number. Following is the code for MediUser : import java.util.Collection; import org.springframework.security.core.GrantedAuthority; import org.springframework.security.core.
Read more

Hibernate Difference between update() and merge()

Image
In order to explain the difference between update and merge, I have created an example, which you can execute or just read it to understand the difference. 1. First Create a database medireports: (DB=MySQL) CREATE DATABASE `medireports` 2. Now Create a 'reports' table: CREATE TABLE `reports` ( `reportid` varchar(20) NOT NULL, `report` mediumblob, `phonenumber` bigint(20) NOT NULL, `labid` varchar(45) DEFAULT NULL, `retainreport` varchar(45) DEFAULT NULL, `reportdate` date DEFAULT NULL, `filename` varchar(65) DEFAULT NULL, PRIMARY KEY (`reportid`) ) 3. Insert data into the reports table: INSERT INTO `medireports`.`reports`(`reportid`,`phonenumber`,`retainreport`,`reportdate`,`filename`) VALUES ('ZL1234', '9999666222', '0', '2014-03-13', 'jqModal.js'); INSERT INTO `medireports`.`reports`(`reportid`,`phonenumber`,`retainreport`,`reportdate`,`filename`) VALUES ('ZL123456&
Read more

Running tomcat maven plugin in Debug mode (in STS, Eclipse and MyEclipse)

Image
Over here I'll explain, as to how to run a tomcat maven plugin in debug mode, in Eclipse and Spring Tool Source (STS). It will be a three step setup and once you are done with the setup, you can run the tomcat server in debug mode with just one click. Following are the setup steps: Step 1 : Entering maven dependency for tomcat in pom.xml file Step 2 : Creating debug configuration Step 3 : Running tomcat server in debug mode Step 1: Entering maven dependency for tomcat in pom.xml file Open your pom.xml file. Enter the tomcat plugin dependency, as shown in the following figure: Now right click on the pom.xml and select Run As à Maven Install . Step 2 :  Creating Debug Configuration Right click on pom.xml and select Debug As à Debug Configurations… A Debug Configurations window will open, as shown in the following figure: On the left hand window right click on Maven Build , as a result, following screen will get displayed:
Read more