RestAssured multipart file upload

Carvia Tech | September 12, 2020 | 3 min read | 5,051 views | Rest Assured

In this article we will learn how to test multipart/form-data file upload feature using RestAssured library, various assertions, and kotlin support.

Let’s assume you have a fileupload server that accepts a param + a file and returns a json with upload status. You can download such Spring Boot based server from this github repository:

Optionally, you can follow Spring Boot file upload with Gradle, Kotlin and Junit 5 to setup the file upload server.

REST Assured gradle setup

We will add the latest rest-assured dependencies to our gradle build file.

dependencies {
    testImplementation ''
    testImplementation ''
    testImplementation ''
    testImplementation group: '', name: 'rest-assured', version: '4.1.2'

test {
	useJUnitPlatform()  (1)
1 Configuring JUNIT 5 Platform

You can check the latest version of rest-assured artifacts from

REST Assured File Upload

Now we will develop a RestAssured test that uploads a file and validate the status.

Let’s assume that file upload controller has signature similar to depicted by the below HTML form:

HTML form for file upload with multipart/form-data
<form id="uploadForm" action="/fileupload" method="post" enctype="multipart/form-data">
        <input type="file" name="file" size="40">
        <input type=submit value="Upload!">

The server response for successful file upload looks like this:

File upload response
  "success": true
import io.restassured.http.ContentType;
import org.junit.jupiter.api.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Date;

import static io.restassured.RestAssured.given;
import static org.hamcrest.core.IsEqual.equalTo;

public class FileUploadTest {

    private final Logger logger = LoggerFactory.getLogger(FileUploadTest.class);

    public void fileUploadTest() {
            .param("timestamp", new Date().getTime())
            .multiPart("file", new File("/path/to/file.json"))
            .body("success", equalTo(true));

REST Assured FileUpload Kotlin version

REST Assured has introduced a new module called "kotlin-extensions" which provides useful extension functions when working with Kotlin.

You can add this kotlin extension library to your project to start developing beautiful rest assured testcases written in kotlin.

testImplementation ''

For maven users:


Advantages with Kotlin

Besides a more pleasing API for Kotlin developers it also has a couple of major benefits to the Java API:

  1. All failed expectations are reported at the same time

  2. Formatting the code in your IDE won’t mess up indentation

The same file upload testcase in Kotlin will look like below:

REST Assured based Fileupload testcase in Kotlin
fun `test rest assured file upload with kotlin`() {
    val success: Boolean =
        Given {
            multiPart("file", File("/path/to/file.json"))
        } When {
        } Then {
            body("success", equalTo(true))
        } Extract {
    println("operation status = $success")

That’s all.

You can download source for this article from Github repository:

Rest Assured:
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  3. REST Assured Basic Authentication
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