diff --git a/docs/testing/assertions.md b/docs/testing/assertions.md
index 5703cf44..2d272240 100644
--- a/docs/testing/assertions.md
+++ b/docs/testing/assertions.md
@@ -5,4 +5,7 @@ Assertions allow you to declaratively write tests.
 This should cover most of your testing needs. For complex tests, you can write test scripts.
 
 **Example:**
-![bru assertions](../public/images/assertions.png)
\ No newline at end of file
+![bru assertions](../public/images/assertions.png)
+
+## Accessing headers
+To access HTTP response headers, you can query `res.headers.['xyz]` (whereas `xyz` is the lower-cased header name like `x-powered-by`for example). Be aware that accessing inexistent headers will result in an error, as an inexistent header is not an empty string, but "undefined".