Testing a User Interface using Canopy

Testing a user interface is a challenging task in programming. However, new tools have emerged to make this better feasible. Using the setup of an web app using the SAFE template, canopy is a testing library that enables UI testing in the browser.

One of the best programming practices is the use of a REPL (Run Evaluate Print Loop). F# uses script files and the FSI for this process. Normally I develop code in an script file run it in the REPL and continue until I have created a specific feature. Ideally, the same can be applied to setting up and running tests.

The first step is to import the needed libraries in the script file. With the pakket manager Paket, there is an option to have a script file generated that will reference all the needed libraries for a specific project. This can be done command line:


Or a directive can be added in the paket.dependencies file:

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The resulting references script file can be loaded in the script file used to create the tests. First the project is started up for development. Then the script file with tests is run in the REPL. This will fire up a browser, load the application and run the UI tests:

#load "./../../../.paket/load/net472/UITests/uitests.group.fsx"

open System.IO
open canopy.runner.classic
open canopy.configuration
open canopy.classic
open canopy.types

let filepath = __SOURCE_DIRECTORY__
let driverpath =
let chromepath = Path.Combine(filepath, driverpath)

type PageIds =
    | Parent of string * PageIds list
    | Child of string

module Literals =
    // starting div for the elmish app
    let appId = "#elmish-app"

    let homePageId = "#homepage"

    let appBarId = "#appbar"

    let bottomBarId = "#bottombar"

    let bodyId = "#body"

    let title = "GenPRES"

let checkPageDivs ids =
    let rec check previd ids =
        match ids with
        | [] -> ()
        | p :: cs ->
            match p with
            | Child id ->
                if previd = "" then
                    sprintf "checking single: %s" id |> describe
                    displayed id
                    sprintf "checking child: %s of parent: %s" id previd
                    |> describe
                    (element previd |> elementWithin id) |> displayed
            | Parent(p, cs_) ->
                if previd = "" then
                    sprintf "checking main: %s" p |> describe
                    displayed p
                    sprintf "checking child: %s of parent: %s" p previd
                    |> describe
                    (element previd |> elementWithin p) |> displayed
                check p cs_
            check previd cs
    check "" ids

chromeDir <- chromepath
suites <- [ suite() ]
start chrome
"check if the app is correctly loaded" &&& fun _ ->
    // go to the url
    url "http://localhost:8080/"
    describe "checking loaded page ids for the home page"
    [ Parent(Literals.appId,
             [ Parent(Literals.homePageId,
                      [ Child Literals.appBarId
                        Child Literals.bodyId
                        Child Literals.bottomBarId ]) ]) ]
    |> checkPageDivs
    describe "check if the page title is GenPRES"
    "GenPRES" === title()
    describe "check if the appbar title is GenPRES"
    let title = (element "#appbar" |> elementWithin "#title")
    "GenPRES" === (read title)

The results look like:

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