stracker-phil / codeceptjs-pixelmatchhelper Goto Github PK

Suppose I have no base screenshot created yet. I'm trying this:

Feature('My');

Scenario('test something',  ({ I }) => {
    I.amOnPage("https://codecept.io");
    I.wait(5);
    I.saveElementScreenshot(".sub-bar", "Bar.png");
    I.checkVisualDifferences("Bar.png");
});

But when I run the test, a base screenshot of whole page is created instead of the element .sub-bar only.

In codeceptjs-resemblehelper I do it this way:

Feature('My');

Scenario('test something',  ({ I }) => {
    I.amOnPage("https://codecept.io");
    I.wait(5);
    I.saveElementScreenshot(".sub-bar", "Bar.png");
    I.seeVisualDiff("Bar.png", { prepareBaseImage: true, tolerance: 0 });
});

and you get a base screenshot of the element only as expected.

Actual: The diff-images are not embedded in Allure reports. Only Wrapped Error message is displayed
Expected: The diff-images should be embedded in Allure reports

Currently getVisualDifference just throws generic errors. Thus, a client cannot implement their own error handling. My suggestion would be to implement specific exceptions in order for them to be handled individually.

This would especially allow to still diff images which have different dimensions (e.g. by all expected images to match the actual image).
Of course an option would need to be introduced to fallback to current behaviour, too.

Motivation:
If due to some change an element gets added to a website, or some elements have different sizes, the dimensions won't be the same, however a diff can help identify the problem easily.

Will come back to this with a PR as soon as time comes by.

For my visual regression tests I like to have diff images and diff calculation even if the dimensions of the images mismatch. This could e.g. occur between two website screenshots if an additional line of text was added.

While this could be incorporated directly in pixelmatch as well as codeceptjs-pixelmatchhelper I more or less agree with mapbox/pixelmatch#25 (comment) in it being easy to do outside and adding another dependency like sharp just for edge cases should in general be avoided.

Nevertheless I think documenting the solution would help. So perhaps this could be added to the wiki/FAQ:

I created a custom function for my steps-file.js which is just called before a this.getVisualDifferences() and increases the smaller screenshot with black pixels. Yes this overrides both files, but is the most versatile solution.

const fs = require('fs');
const sharp = require('sharp');
...
async adaptImageCanvasForCompareIfNecessary(fileExpected, fileActual) {
	const expectedImage = sharp(fs.readFileSync(fileExpected));
	const actualImage = sharp(fs.readFileSync(fileActual));
	const expectedImageMetadata = await expectedImage.metadata();
	const actualImageMetadata = await actualImage.metadata();
	const maximumWidth = Math.max(expectedImageMetadata.width, actualImageMetadata.width);
	const maximumHeight = Math.max(expectedImageMetadata.height, actualImageMetadata.height);

	if (expectedImageMetadata.width !== actualImageMetadata.width
	|| expectedImageMetadata.height !== actualImageMetadata.height) {
		this.say(`Screenshots have different dimensions; increasing canvas to ${maximumWidth}x${maximumHeight}`);
		const newExpectedImage = await expectedImage
			.resize({
				width: maximumWidth,
				height: maximumHeight,
				fit: 'contain',
				position: 'left top'
			})
			.png()
			.toFile(fileExpected);
		const newActualImage = await actualImage
			.resize({
				width: maximumWidth,
				height: maximumHeight,
				fit: 'contain',
				position: 'left top'
			})
			.png()
			.toFile(fileActual);
	}
},
...

Hi!
There is issue when run tests in docker:
fs.renameSync(); (480 line) throws an exception:
Error: EXDEV: cross-device link not permitted, rename '/codecept/output/~60mi4.temp' -> '/codecept/tests/output/debug.png' at Object.renameSync (node:fs:993:3) at PixelmatchHelper._takeScreenshot (node_modules/codeceptjs-pixelmatchhelper/index.js:479:6) at async PixelmatchHelper._maybeCaptureImage (node_modules/codeceptjs-pixelmatchhelper/index.js:639:3) at async PixelmatchHelper.getVisualDifferences (node_modules/codeceptjs-pixelmatchhelper/index.js:280:3) at async /codecept/node_modules/codeceptjs-pixelmatchhelper/index.js:241:5
It could be fixed by changing method to fs.copyFileSync();

Hi, I just started with this helper and immediately run into a problem using WebDriver.
The saveScreenshot function doesn't accept files with .temp file type.

It throws an error when running the test:

Is there a chance to fix this? Thanks in advance.