rest-assured/src/main/java/io/restassured/builder/ResponseSpecBuilder.java
public ResponseSpecBuilder addResponseSpecification(ResponseSpecification specification) {
        if (!(specification instanceof ResponseSpecificationImpl)) {
            throw new IllegalArgumentException("specification must be of type " + ResponseSpecificationImpl.class.getClass() + ".");
        }

        ResponseSpecificationImpl rs = (ResponseSpecificationImpl) specification;
        SpecificationMerger.merge((ResponseSpecificationImpl) spec, rs);
        return this;
    }
public ResponseSpecBuilder addResponseSpecification(ResponseSpecification specification) {
        if (!(specification instanceof ResponseSpecificationImpl)) {
            throw new IllegalArgumentException("specification must be of type " + ResponseSpecificationImpl.class.getClass() + ".");
        }

        ResponseSpecificationImpl rs = (ResponseSpecificationImpl) specification;
        SpecificationMerger.merge((ResponseSpecificationImpl) spec, rs);
        return this;
    }
Merge this builder with settings from another specification. Note that the supplied specification
can overwrite data in the current specification. The following settings are overwritten:
<ul>
<li>Content type</li>
<li>Root path</
<li>Status code</li>
<li>Status line</li>
</ul>
The following settings are merged:
<ul>
<li>Response body expectations</li>
<li>Cookies</li>
<li>Headers</li>
</ul>

@param specification The specification the add.
@return The builder