Elemental Selenium
The Problem
Just like with uploading files we hit the same issue with downloading them. A dialog box just out of Selenium's reach.
A Solution
With some additional configuration when loading Selenium we can easily side-step the dialog box. This is done by instructing the browser to download files to a specific location without being prompted.
After the file is downloaded we can then perform some simple checks to make sure the file is what we expect.
Let's dig in with an example.
An Example
Let's start off by pulling in our requisite libraries (e.g., to drive the browser, and for assertions, to help create a uniquely named temporary download directory, and to create & destroy the temp directory) and wiring up our method.
Our method is where the magic is happening in this example. In it we're creating a uniquely named temp directory and storing the absolute path of it in an instance variable that we'll use throughout this file.
We're also configuring a browser profile object (for Firefox in this case) and plying it with the necessary configuration parameters to make it automatically download the file where we want. Here's a breakdown of each of them:
- accepts a string. This is how we set the custom download path. It needs to be an absolute path.
- takes a number. It tells Firefox which download directory to use. tells it to use a custom download path, wheras would use the browser's default path, and would place them on the Desktop.
- tells Firefox when not to prompt for a file download. It accepts a string of the file's MIME type. If you want to specify more than one, you do it with a comma-separated string.
- is for when downloading PDFs. This overrides the sensible default in Firefox that previews PDFs in the browser. It accepts a boolean.
This profile object is then passed into our instance of Selenium.
Now let's add some and methods.
In we make sure to clean up the temp directory after closing the browser. Other than that, it's business as usual.
Now onto the test itself.
After loading the page we find the first download link and click it. The click triggers an automatic download to the temp directory created in . After that, we perform some rudimentary checks to make sure the directory isn't empty and that the file isn't empty either.
Expected Behavior
When you save this file and run it (e.g., from the command-line) here is will happen.
- Create a uniquely named temp directory
- Load the browser
- Visit the page
- Find and click the first download link on the page
- Automatically download the file to the temp directory without prompting
- Check that the temp directory is not empty
- Check that the downloaded file is not empty
- Close the browser
- Delete the temp directory and it's contents
Outro
A similar approach can be applied to some other browsers with varying configurations. But downloading files this way is not sustainable or recommended. Mark Collin articulates this point well in his prominent write-up about it here.
In a future tip I'll cover a more reliable, faster, and scalable browser agnostic approach to downloading files.
Until then, Happy Testing!
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