Take a look at-Driving HTML Templates

After a decade or extra the place Single-Web page-Functions generated by
JavaScript frameworks have
turn out to be the norm, we see that server-side rendered HTML is turning into
in style once more, additionally because of libraries comparable to HTMX or Turbo. Writing a wealthy net UI in a
historically server-side language like Go or Java is not simply doable,
however a really enticing proposition.

We then face the issue of how one can write automated assessments for the HTML
elements of our net purposes. Whereas the JavaScript world has advanced highly effective and refined methods to check the UI,
ranging in measurement from unit-level to integration to end-to-end, in different
languages we shouldn’t have such a richness of instruments obtainable.

When writing an online utility in Go or Java, HTML is usually generated
by templates, which include small fragments of logic. It’s actually
doable to check them not directly by end-to-end assessments, however these assessments
are sluggish and costly.

We are able to as a substitute write unit assessments that use CSS selectors to probe the
presence and proper content material of particular HTML parts inside a doc.
Parameterizing these assessments makes it simple so as to add new assessments and to obviously
point out what particulars every take a look at is verifying. This method works with any
language that has entry to an HTML parsing library that helps CSS
selectors; examples are offered in Go and Java.

Stage 1: checking for sound HTML

The primary factor we need to verify is that the HTML we produce is
mainly sound. I do not imply to verify that HTML is legitimate in accordance with the
W3C; it might be cool to do it, however it’s higher to begin with a lot less complicated and sooner checks.
As an example, we would like our assessments to
break if the template generates one thing like

<div>foo</p>

Let’s examine how one can do it in levels: we begin with the next take a look at that
tries to compile the template. In Go we use the usual html/template bundle.

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    _ = templ
  }

In Java, we use jmustache
as a result of it is quite simple to make use of; Freemarker or
Velocity are different widespread selections.

Java

  @Take a look at
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
  }

If we run this take a look at, it can fail, as a result of the index.tmpl file does
not exist. So we create it, with the above damaged HTML. Now the take a look at ought to go.

Then we create a mannequin for the template to make use of. The appliance manages a todo-list, and
we are able to create a minimal mannequin for demonstration functions.

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    mannequin := todo.NewList()
    _ = templ
    _ = mannequin
  }

Java

  @Take a look at
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
      var mannequin = new TodoList();
  }

Now we render the template, saving the ends in a bytes buffer (Go) or as a String (Java).

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    mannequin := todo.NewList()
    var buf bytes.Buffer
    err := templ.Execute(&buf, mannequin)
    if err != nil {
      panic(err)
    }
  }

Java

  @Take a look at
  void indexIsSoundHtml() {
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
      var mannequin = new TodoList();
  
      var html = template.execute(mannequin);
  }

At this level, we need to parse the HTML and we count on to see an
error, as a result of in our damaged HTML there’s a div component that
is closed by a p component. There may be an HTML parser within the Go
normal library, however it’s too lenient: if we run it on our damaged HTML, we do not get an
error. Fortunately, the Go normal library additionally has an XML parser that may be
configured to parse HTML (because of this Stack Overflow reply)

  func Test_wellFormedHtml(t *testing.T) {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    mannequin := todo.NewList()
    
    // render the template right into a buffer
    var buf bytes.Buffer
    err := templ.Execute(&buf, mannequin)
    if err != nil {
      panic(err)
    }
  
    // verify that the template might be parsed as (lenient) XML
    decoder := xml.NewDecoder(bytes.NewReader(buf.Bytes()))
    decoder.Strict = false
    decoder.AutoClose = xml.HTMLAutoClose
    decoder.Entity = xml.HTMLEntity
    for {
      _, err := decoder.Token()
      swap err {
      case io.EOF:
        return // We're completed, it is legitimate!
      case nil:
        // do nothing
      default:
        t.Fatalf("Error parsing html: %s", err)
      }
    }
  }

	characteristic	CSS selector
①	All of the objects	ul.todo-list li
②	Accomplished objects	ul.todo-list li.accomplished
⓷	Gadgets left	span.todo-count
④	Highlighted navigation hyperlink	ul.filters a.chosen
⑤	Clear accomplished button	button.clear-completed

Take a look at-Driving HTML Templates

Stage 1: checking for sound HTML

Stage 2: testing HTML construction

What else ought to we take a look at?

Testing HTML content material

Take a look at each content material and soundness on the identical time

The second take a look at

Make it simple so as to add new assessments

Making the desk extra expressive, on the expense of the take a look at code

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