modules/spring-mock-mvc/src/main/java/io/restassured/module/mockmvc/specification/MockMvcRequestSpecBuilder.java
public MockMvcRequestSpecBuilder addMultiPart(String controlName, String fileName, byte[] bytes) {
        spec.multiPart(controlName, fileName, bytes);
        return this;
    }
public MockMvcRequestSpecBuilder addMultiPart(String controlName, String fileName, byte[] bytes) {
        spec.multiPart(controlName, fileName, bytes);
        return this;
    }
Specify a byte-array to upload to the server using multi-part form data.
It will use the content-type <tt>application/octet-stream</tt>. If this is not what you want please use an overloaded method.

@param controlName Defines the control name of the body part. In HTML this is the attribute name of the input tag.
@param fileName    The name of the content you're uploading
@param bytes       The bytes you want to send
@return The request specification