updated testing docs
Update testing.rst

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Pin reversion version
Merge pull request #3218 from yakky/feature/pin_reversion

Pin reversion
Merge pull request #3215 from ojii/3214-testing-docs

updated testing docs
Add test for view_url render_model attribute
Fix view_url render_model attribute
Merge pull request #3221 from yakky/feature/fix_view_url

Fix view url