Advanced Settings


By default Needle uses the PIL engine (needle.engines.pil_engine.Engine) to take screenshots. Instead of PIL, you may also use PerceptualDiff or ImageMagick.

Example with PerceptualDiff:

pytest --driver Chrome --needle-engine perceptualdiff

Example with ImageMagick:

pytest --driver Chrome --needle-engine imagemagick

Besides being much faster than PIL, PerceptualDiff and ImageMagick also generate a diff PNG file when a test fails, highlighting the differences between the baseline image and the new screenshot.

Note that to use the PerceptualDiff engine you will first need to download the perceptualdiff binary and place it in your PATH.

To use the ImageMagick engine you will need to install a package on your machine (e.g. sudo apt-get install imagemagick on Ubuntu or brew install imagemagick on OSX).

File cleanup

Each time you run tests, Needle will create new screenshot images on disk, for comparison with the baseline screenshots. It’s then up to you whether you want to delete them or archive them. To remove screenshots from successful test use:

pytest --driver Chrome --needle-cleanup-on-success

Any unsuccessful tests will remain on the file system.

File output

To specify a path for baseline image path use:

pytest --driver Chrome --needle-baseline-dir /path/to/baseline/images

Default path is ./screenshots/baseline

To specify a path for output image path use:

pytest --driver Chrome --needle-output-dir /path/to/output/images

Default path is ./screenshots

Generating HTML reports

To generate html reports use:

pytest --driver Chrome --html=report.html --self-contained-html