diff --git a/testing/lisp/test-ob.el b/testing/lisp/test-ob.el
index c8dbd44f4..2b9326865 100644
--- a/testing/lisp/test-ob.el
+++ b/testing/lisp/test-ob.el
@@ -314,6 +314,151 @@ this is simple"
     (org-babel-next-src-block)
     (should (= 14 (org-babel-execute-src-block)))))
 
+
+(ert-deftest test-ob/merge-params ()
+  "Test the output of merging multiple header parameters.  The
+expected output is given in the contents of the source code block
+in each test.  The desired test header parameters are given
+either as a symbol or a list in the `idtest-alist' variable.
+Multiple header parameters must be separated by a newline and
+exactly two spaces in the block contents."
+  (let ((test-the-result
+         (lambda (test-prop)
+           (org-babel-next-src-block)
+           (org-set-regexps-and-options)
+           (string=
+            (if (string= "symbol" (type-of test-prop))
+                (format "%s" (assoc test-prop (nth 2 (org-babel-get-src-block-info))))
+              (mapconcat
+               (lambda (x) (format "%s" (assoc x (nth 2 (org-babel-get-src-block-info)))))
+               test-prop "\n  ")) ;; newline with exactly two spaces.
+            (string-trim (org-element-property :value (org-element-at-point)))))))
+    (should ;; 1. inherit-document-header-args
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+#+begin_src conf
+  (:tangle . /tmp/default_tangle.txt)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should  ;; 2. inherit-document-header-with-local-sync-action
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+#+begin_src conf :tangle skip
+  (:tangle . /tmp/default_tangle.txt skip)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should ;; 3. override-document-header-with-local-tfile
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+#+begin_src conf :tangle randomfile sync
+  (:tangle . randomfile sync)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should  ;; 4. override-document-and-parent-header-with-local-tfile-and-action
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+:PROPERTIES:
+:header-args: :tangle \"newfile.txt\" import
+:END:
+** Two
+#+begin_src conf :tangle randomfile sync
+  (:tangle . randomfile sync)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should ;; 5. test-tangle-and-default-results-param-together
+     (org-test-with-temp-text
+         "\
+* One
+#+begin_src conf  :tangle randomfile
+  (:tangle . randomfile)
+  (:results . replace)
+#+end_src"
+       (funcall test-the-result '(:tangle :results))))
+    (should  ;; 6. inherit-document-tfile-take-only-last-local-sync-action
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+#+begin_src conf  :tangle import export
+  (:tangle . /tmp/default_tangle.txt export)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should  ;; 7. ignore-document-header-take-last-tfile-and-sync-action
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+#+begin_src conf  :tangle fname1 fname2 sync export
+  (:tangle . fname2 export)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should  ;; 8. test-results-and-exports
+     (org-test-with-temp-text
+         "\
+* One
+#+begin_src sh :results file wrap
+  (:results . wrap file replace)
+  (:exports . code)
+#+end_src"
+       (funcall test-the-result '(:results :exports))))
+    (should-not  ;; 9. do-not-tangle-this-block --
+     ;; THIS SHOULD NOT FAIL WITH NEW MERGE FUNCTION.
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+#+begin_src conf :tangle no
+  (:tangle . no)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should  ;; 10. test-tangle-exports-and-comments
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+:PROPERTIES:
+:header-args: :tangle no :exports verbatim
+:END:
+#+begin_src conf :tangle \"foo.txt\" :comments link
+  (:tangle . foo.txt)
+  (:exports . verbatim code)
+  (:comments . link)
+#+end_src"
+       (funcall test-the-result '(:tangle :exports :comments))))
+    (should  ;; 11. override-document-and-heading-tfile-with-yes
+     (org-test-with-temp-text
+         "\
+#+PROPERTY: header-args :tangle /tmp/default_tangle.txt
+* One
+:PROPERTIES:
+:header-args: :tangle \"foo.txt\"
+:END:
+#+begin_src conf :tangle yes
+   (:tangle . foo.txt)
+#+end_src"
+       (funcall test-the-result :tangle)))
+    (should-not  ;; 12. tangle-file-with-spaces
+     ;; THIS SHOULD NOT FAIL WITH NEW MERGE FUNCTION.
+     (org-test-with-temp-text
+         "\
+* One
+:PROPERTIES:
+:header-args: :tangle \"foo.txt\"
+:END:
+** Two
+#+begin_src conf :tangle \"file with spaces.txt\"
+   (:tangle . \"file with spaces.txt\")
+#+end_src"
+       (funcall test-the-result :tangle)))))
+
 (ert-deftest test-ob/inline-src-blocks ()
   (should
    (= 1