Patch files

Use the --patch-only=<patch-file> argument to define a patch file - Diffblue Cover will only write tests for the code changes defined in the patch file (any class in the patch and any related/dependent classes).

Command line argument

Usage: --patch-only=<patch-file>

Alternative: -p=<patch-file>

Example: --patch-only=path/to/file.patch

  • Use diff or a similar tool to create a patch file for your changes in your project - for example: git diff origin/develop > file.patch.

  • For a multi-module project, generate the patch at the root of the project and provide the absolute path to the patch file, using --working-directory with the relative path to the module. The same patch file can be used for each module.

  • For a project without modules, or a project where tests will only ever be created for a single module, where --working-directory is not used, the relative path to the patch file for the project or module only may be used - for example:

    cd Module
    git diff origin/develop --relative > file.patch
  • The --patch-only argument only accepts files in UTF-8 encoding. If using PowerShell on Windows, use the following command to get the patch in UTF-8 instead of the default UTF-16:

    git diff origin/develop | out-file file.patch -encoding utf8

Create a patch file

The exact patch file you need depends on your setup, but here are some examples using git diff. The variable DIFFBLUE_PATCH represents the name of your patch file.

For a patch containing commits newer than the project's origin (i.e. the corresponding branch on the remote repository your local branch was created from):

git diff $(git rev-parse --abbrev-ref HEAD)...HEAD > $DIFFBLUE_PATCH

For a patch containing commits on your branch newer than those on the local copy of TARGET_BRANCH (e.g. where TARGET_BRANCH is develop):


For a patch containing commits on your branch newer than those on the remote host TARGET_BRANCH (e.g. where REMOTE is origin and REMOTE/TARGET_BRANCH is origin/develop):

git fetch REMOTE

For a patch containing only currently uncommitted changes:

git diff > $DIFFBLUE_PATCH

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