Rest API Automation in Java - Post Method

Using Rest-assured and TestNG

In this post, we will learn to automate REST APIs using Rest-Assured library and TestNG. Rest Assured is a Java library using which we can test and validate the REST web services. Although Rest-assured provides its own validating mechanism(assertions for validating response) but we can combine Rest-assured with TestNG to get the best of both the libraries.

During the course of this tutorial, we will be using the following-

• Sample Rest API to be used in Automation - RestCountries API
• Rest-Assured and its dependencies (https://code.google.com/p/rest-assured/wiki/Downloads) (Remember to download and add to class path, the other dependencies also). POM dependencies for the Rest Assured and its dependencies-

<dependency>
    <groupId>io.rest-assured</groupId>
    <artifactId>rest-assured</artifactId>
    <version>3.1.1</version>
</dependency>

• TestNG as testing framework

Automating Rest API HTTP Post method

The following code snippet uses requestSpecBuilder to create a post request. We have used the following parameters in our code, you need to set them as per your requirement-

1. APIUrl - Set APIUrl variable with the URL of the Rest API
2. APIBody - Set APIBody variable with body of the Rest API containing parameters e.g. {"key1":"value1","key2":"value2"}
3. setContentType() - Pass the "application/json", "application/xml" or "text/html" etc. headers to setContenType() method
4. Authentication credentials - Pass the username and password to the basic() method and in case of no authentication leave them blank basic("","")

The comments in the following code make it self-explanatory.

	package test.qaearth;
	import org.testng.Assert;
	import org.testng.annotations.Test;
	import static io.restassured.RestAssured.given;
	import java.util.List;
	import io.restassured.builder.RequestSpecBuilder;
	import io.restassured.http.ContentType;
	import io.restassured.response.Response;
	import io.restassured.specification.RequestSpecification;
	public class RestTestPOST {
	@Test
	public void httpPost() {
	// Initializing Rest API's URL
	String APIUrl = "http://{API URL}";
	// Initializing payload or API body
	String APIBody = "{API Body}";
	// e.g.-
	// "{\"key1\":\"value1\",\"key2\":\"value2\"}"
	// Building request using requestSpecBuilder
	RequestSpecBuilder builder = new RequestSpecBuilder();
	// Setting API's body
	builder.setBody(APIBody);
	// Setting content type as application/json or application/xml
	builder.setContentType("application/json; charset=UTF-8");
	RequestSpecification requestSpec = builder.build();
	// Making post request with authentication, leave blank in case there
	// are no credentials- basic("","")
	Response response = given().authentication().preemptive().basic("username", "password").spec(requestSpec).when()
	.post(APIUrl);
	// Fetching param
	List alpha3Code = response.then().contentType(ContentType.JSON).extract().path("key");
	// Asserting that capital of Norway is Oslo
	Assert.assertEquals(alpha3Code.get(0), "Expected value");
	}
	}

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