Using Cypress and R Shiny: Mastering SelectizeInput Elements for Comprehensive UI Testing

Cypress and R Shiny: Working with `selectizeInput` Elements

Introduction

As a developer, writing end-to-end tests for user interface (UI) applications can be a challenging task. In this blog post, we will explore how to use Cypress, a popular testing framework, to test UI elements in an R Shiny application that uses the selectizeInput component.

The selectizeInput is a custom input element provided by the Shiny library, which offers additional features and styling compared to the standard HTML5 select control. In this post, we will delve into how to use Cypress to interact with selectizeInput elements in an R Shiny application.

Understanding `selectizeInput` Elements

The selectizeInput component is used in Shiny applications to create customizable select controls. It consists of two main parts: the visible input element and a hidden select element that stores the selected value. The visible input element provides additional features, such as multi-select capabilities.

When using Cypress to test UI elements, it’s essential to understand how these components work behind the scenes. In this case, we need to consider the relationship between the visible selectizeInput element and its corresponding hidden select element.

Cypress Test Example

Let’s take a look at an example of how you might write a Cypress test for the R Shiny application provided:

// Test the initial value of hidden select
cy.get('select#element1')
  .should('have.value', 'descriptive')
  .find('option')
  .should('have.length', 1)             // only one option on the select

const choices = ['descriptive', 'comparative', 'neutral']

choices.forEach(choice =&gt; {
 
  cy.get('select#e1')
    .next()                        // access the UI block
    .click()                       // open the "select"
    .contains(choice)              // chose this choice
    .click()

  // Test the new value of hidden select
  cy.get('select#e1')
    .should('have.value', choice)
})

This test first checks that the initial value of the selectizeInput element is set to “descriptive”. It then uses a loop to test each of the available choices.

Accessing Hidden Select Elements

When interacting with hidden elements in Cypress, it’s essential to understand how they are structured. In this case, we need to access the hidden select element that stores the selected value.

To achieve this, we can use several techniques:

Using the .next() command to move up the DOM tree and access the hidden select element.
Using the .find() command to search for the desired element within the visible selectizeInput element.
Using the .contains() command to verify that a specific text content is present in an element.

Tips and Variations

Here are some additional tips and variations you might find useful when working with selectizeInput elements in Cypress:

To open the dropdown menu, use the .click() command on the visible selectizeInput element.
To select a specific option within the dropdown menu, use the .contains() command followed by the desired text content.
To verify that the selected value has changed, use the .should('have.value', 'newValue') command.

Conclusion

In this blog post, we have explored how to use Cypress to test UI elements in an R Shiny application that uses the selectizeInput component. By understanding how these components work behind the scenes and using various techniques for interacting with hidden elements, you can write comprehensive tests that cover your application’s functionality.

Remember to keep your tests concise, readable, and well-structured. This will make it easier to maintain and modify them over time as your application evolves.

Last modified on 2024-02-23

Cypress and R Shiny: Working with selectizeInput Elements