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+# Bisecting a Regression
+
+## At a minimum you'll need:
+-git (on windows http://code.google.com/p/msysgit/downloads/list?q=full+installer+official+git)
+-a server, if you have python installed that will work
+
+## Getting pdf.js
+-startup the git command line from above
+-move a directory where you want it to live, if you're using a server that isn't python go into the directory where your wwwroot is
+-`git clone https://github.com/mozilla/pdf.js.git`
+
+### Option 1 - Python Server
+- `cd pdf.js/test`
+- `python test.py --noDownload`
+- open firefox and check http://localhost:8080/web/viewer.html goes to the pdf viewer
+
+### Option 2 - Other Server
+- go to http://<yourserver>/pdf.js/web/viewer.html
+
+## Verify the Regression
+- Download Bad PDF and save it in pdf.js/test/pdfs
+- go to <url from above>?file=../test/pdfs/<name of pdf> and verify the PDF works
+
+## Start the bisecting process
+- Mark the current version is bad using `git bisect start` and `git bisect bad`
+
+## Now find bad commit id
+
+### Option 1 - Detecting version / commit of the pdf.js installed in the Firefox
+- Open resource://pdf.js/build/pdf.js
+- Find commit in the line with 'PDFJS.build = '
+- Find version in the line with 'PDFJS.version = '
+
+### Option 2 - Using bugzilla patch
+- A bugzilla patch contains the commits information near '
+browser/extensions/pdfjs/content/build/pdf.js'
+ [e.g. see https://bug871530.bugzilla.mozilla.org/attachment.cgi?id=750657, was added3d (good), will be 869b878 (bad)]
+
+### Option 3 - Using MXR
+- If you know it was good in beta or aurora get the bad commit id from mxr
+Find the line with 'PDFJS.build = ' and copy the value in the single quotes e.g. 4e83123
+auora - http://mxr.mozilla.org/mozilla-aurora/source/browser/extensions/pdfjs/content/build/pdf.js#24
+beta - http://mxr.mozilla.org/mozilla-beta/source/browser/extensions/pdfjs/content/build/pdf.js#24
+
+## Verify the Working Version
+- `git checkout <commit id that you found above>`
+- Full refresh(ctr+shift+r) Firefox and verify the PDF no longer works.
+- Mark it as good `git bisect good`
+
+## Continue bisecting
+- Full refresh(ctr+shift+r) of the viewer in Firefox
+- If the current version works `git bisect good`
+- If it fails `git bisect bad`
+- Repeat same steps as above if it's bad `git bisect bad` if it's good `git bisect good`