diff --git a/packages/common/http/testing/src/request.ts b/packages/common/http/testing/src/request.ts
index 59a18749ed..022cf77e19 100644
--- a/packages/common/http/testing/src/request.ts
+++ b/packages/common/http/testing/src/request.ts
@@ -33,6 +33,8 @@ export class TestRequest {
   /**
    * Resolve the request by returning a body plus additional HTTP information (such as response
    * headers) if provided.
+   * If the request specifies an expected body type, the body is converted into the requested type.
+   * Otherwise, the body is converted to `JSON` by default.
    *
    * Both successful and unsuccessful responses can be delivered via `flush()`.
    */