Minor doc update

Signed-off-by: currantw <[email protected]>

DEVELOPER_GUIDE.rst

@@ -405,7 +405,7 @@ Sample test class:
 Doctest
 >>>>>>>
 
-Python doctest library makes our document executable which keeps it up-to-date to source code. The doc generator aforementioned served as scaffolding and generated many docs in short time. Now the examples inside is changed to doctest gradually. For more details please read `Doctest <./docs/dev/testing-doctest.md>`_.
+Python doctest library makes our document executable which keeps it up-to-date to source code. The doc generator aforementioned served as scaffolding and generated many docs in short time. Now the examples inside is changed to doctest gradually. For more details please read `testing-doctest <./docs/dev/testing-doctest.md>`_.
 
 
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