Test stomp-frame-header and fix encountered bug

stomp.el

@@ -53,7 +53,7 @@
 (defun stomp-frame-header (header frame)
   "Shortcut to access frame headers"
   (assoc-default
-   "content-length"
+   header
    (alist-get 'headers frame nil) 'string-equal nil))
 
 (defun stomp-read-frame (buffer)

test/test.el

@@ -93,3 +93,17 @@
     (map-put frame 'headers headers)
     (map-put frame 'content "Some content")
     (should (equal "SEND\nheader:value\n\nSome content\u0000" (stomp-frame-to-string frame)))))
+
+(ert-deftest can-get-frame-header ()
+  "stomp-frame-header should be able to read arbitrary headers
+   from a frame"
+  (setq frame '((headers . (("bla" . "ok") ("random" . "barry")))))
+
+  (should (equal "ok" (stomp-frame-header "bla" frame)))
+  (should (equal "barry" (stomp-frame-header "random" frame))))
+
+(ert-deftest will-return-nil-for-non-existent-header ()
+    "stomp-frame-header should return nil if a header does not exist"
+  (setq frame '((headers . (("okay" . "bye")))))
+
+  (should (equal nil (stomp-frame-header "bla" frame))))