Recently while working on a project, I had to create a functionality where users can download an excel file consisting of some data.
In this process, since I am a big fan of E2E Testing with Cypress.io, I decided to write a test suite that could make sure that the excel is being downloaded correctly and also consists of the correct data that our users would expect.
This article assumes a basic understanding of cypress.
Disclaimer
If you haven't tried e2e testing with cypress before, I would highly recommend skipping over to the
References📦 Installation
1) Assuming you have a repo named
dashboard-uie2e2)
cdnpm init
npm install cypress --save-dev3) Update the project’s scripts by opening
package.json"scripts": {
"cy:run": "cypress run --headless -b chrome",
"cy:open": "cypress open"
}
4) You should also see some default folders and files created by cypress for you after you have installed cypress.
5) The test that we will write will go inside
integration⚙️ Functionality
For the sake of simplicity, let's say our application only has one feature where users can click on a
download templateOn click of the download template button a file gets downloaded which looks something like this:
Demo
🧪 E2E Testing
1) Create a new file inside
integrationExcelDownload.spec.js2) Inside this file our test would first start with checking for existence of our button and then we will click on it.
cy.get("[data-test-id=export-template-btn")
.should("be.visible")
.click();3) After clicking on it, the file should ideally have been downloaded and now we need to somehow read that file and check if it exists and also check if it consists of the right data in it.
4) To do that, we will first need to install another npm package which can parse the excel and convert it to a json
npm install node-xlsx --save-dev5) After this inside your
plugins/index.jsconst xlsx = require("node-xlsx").default;
const fs = require("fs");
const path = require("path");
module.exports = (on, config) => {
// `on` is used to hook into various events Cypress emits
on("task", {
parseXlsx({ filePath }) {
return new Promise((resolve, reject) => {
try {
const jsonData = xlsx.parse(fs.readFileSync(filePath));
resolve(jsonData);
} catch (e) {
reject(e);
}
});
}
});
};This function will parse our excel file and convert it to json.
6) Finally let’s complete our test for excel file download
// data to check against
const data = [
"id",
"config_sku",
"simple_sku",
"fallback_type",
"field",
"value",
"command"
];
// check for existence of the button on the ui and then click it
cy.get("[data-test-id=export-template-btn")
.should("be.visible")
.click();
// arbitrary wait so that the download can complete
cy.wait(2000);
// call the parseXlsx task we created above to parse the excel and return data as json
cy.parseXlsx("/Users/Downloads/overrides-template.xlsx").then(
jsonData => {
// finally we write the assertion rule to check if that data matches the data we expected the excel file to have.
expect(jsonData[0].data[0]).to.eqls(data);
}
);7) With this we can be sure that our excel download functionality is working as expected.
Test Execution
8) The only caveat here is how do you know the download path for your CI/CD Pipeline or how can you change that path to something else.
The solution to that is built into cypress. Again inside
plugins/index.json("before:browser:launch", (browser = {}, launchOptions) => {
const downloadDirectory = path.join(__dirname, '..', 'excelDownloads')
if (browser.family === 'chromium') {
launchOptions.preferences.default['download'] = { default_directory: downloadDirectory }
}
return launchOptions;
});Here we are changing the default directory of download to a directory named
excelDownloads💡 Conclusion
In conclusion, E2E tests are really important for every app and you should write one too because this is the closest you can get to test how an actual user will use your application.
And as @tlakomy says:
Sleep better at night with e2e tests and cypress.io
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🚀 References
Previously published at https://dev.to/viveknayyar/e2e-testing-of-excel-downloads-with-cypress-21fb