July 24, 2024
Check-Driving HTML Templates

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

We then face the issue of the way to write automated exams for the HTML
components of our internet purposes. Whereas the JavaScript world has advanced powerful and sophisticated methods to check the UI,
ranging in dimension from unit-level to integration to end-to-end, in different
languages we shouldn’t have such a richness of instruments out there.

When writing an internet utility in Go or Java, HTML is often generated
via templates, which comprise small fragments of logic. It’s actually
doable to check them not directly via end-to-end exams, however these exams
are sluggish and costly.

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

Degree 1: checking for sound HTML

The primary factor we wish to examine is that the HTML we produce is
mainly sound. I do not imply to examine that HTML is legitimate in line with the
W3C; it could be cool to do it, nevertheless it’s higher to start out with a lot easier and quicker checks.
For example, we would like our exams to
break if the template generates one thing like

<div>foo</p>

Let’s examine the way to do it in levels: we begin with the next check that
tries to compile the template. In Go we use the usual html/template package deal.

Go

  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 decisions.

Java

  @Check
  void indexIsSoundHtml() 
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
  

If we run this check, it’ll fail, as a result of the index.tmpl file does
not exist. So we create it, with the above damaged HTML. Now the check ought to move.

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

Go

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

Java

  @Check
  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).

Go

  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

  @Check
  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 wish to parse the HTML and we anticipate 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
commonplace library, however it’s too lenient: if we run it on our damaged HTML, we do not get an
error. Fortunately, the Go commonplace library additionally has an XML parser that may be
configured to parse HTML (because of this Stack Overflow answer)

Go

  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)
    
  
    // examine that the template could 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()
      change err 
      case io.EOF:
        return // We're completed, it is legitimate!
      case nil:
        // do nothing
      default:
        t.Fatalf("Error parsing html: %s", err)
      
    
  

source

This code configures the HTML parser to have the precise degree of leniency
for HTML, after which parses the HTML token by token. Certainly, we see the error
message we wished:

--- FAIL: Test_wellFormedHtml (0.00s)
    index_template_test.go:61: Error parsing html: XML syntax error on line 4: surprising finish component </p>

In Java, a flexible library to make use of is jsoup:

Java

  @Check
  void indexIsSoundHtml() 
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream("/index.tmpl")));
      var mannequin = new TodoList();
  
      var html = template.execute(mannequin);
  
      var parser = Parser.htmlParser().setTrackErrors(10);
      Jsoup.parse(html, "", parser);
      assertThat(parser.getErrors()).isEmpty();
  

source

And we see it fail:

java.lang.AssertionError: 
Anticipating empty however was:<[<1:13>: Unexpected EndTag token [</p>] when in state [InBody],

Success! Now if we copy over the contents of the TodoMVC
template
to our index.tmpl file, the check passes.

The check, nonetheless, is simply too verbose: we extract two helper features, in
order to make the intention of the check clearer, and we get

Go

  func Test_wellFormedHtml(t *testing.T) 
    mannequin := todo.NewList()
  
    buf := renderTemplate("index.tmpl", mannequin)
  
    assertWellFormedHtml(t, buf)
  

source

Java

  @Check
  void indexIsSoundHtml() 
      var mannequin = new TodoList();
  
      var html = renderTemplate("/index.tmpl", mannequin);
  
      assertSoundHtml(html);
  

source

Degree 2: testing HTML construction

What else ought to we check?

We all know that the appears to be like of a web page can solely be examined, finally, by a
human how it’s rendered in a browser. Nevertheless, there may be usually
logic in templates, and we would like to have the ability to check that logic.

One may be tempted to check the rendered HTML with string equality,
however this method fails in follow, as a result of templates comprise quite a lot of
particulars that make string equality assertions impractical. The assertions
grow to be very verbose, and when studying the assertion, it turns into tough
to grasp what it’s that we’re making an attempt to show.

What we’d like
is a way to claim that some components of the rendered HTML
correspond to what we anticipate, and to ignore all the small print we do not
care about.
A technique to do that is by operating queries with the CSS selector language:
it’s a highly effective language that permits us to pick the
components that we care about from the entire HTML doc. As soon as we now have
chosen these components, we (1) rely that the variety of component returned
is what we anticipate, and (2) that they comprise the textual content or different content material
that we anticipate.

The UI that we’re imagined to generate appears to be like like this:

There are a number of particulars which are rendered dynamically:

  1. The variety of objects and their textual content content material change, clearly
  2. The model of the todo-item modifications when it is accomplished (e.g., the
    second)
  3. The “2 objects left” textual content will change with the variety of non-completed
    objects
  4. One of many three buttons “All”, “Energetic”, “Accomplished” can be
    highlighted, relying on the present url; as an example if we determine that the
    url that exhibits solely the “Energetic” objects is /lively, then when the present url
    is /lively, the “Energetic” button must be surrounded by a skinny crimson
    rectangle
  5. The “Clear accomplished” button ought to solely be seen if any merchandise is
    accomplished

Every of this issues could be examined with the assistance of CSS selectors.

It is a snippet from the TodoMVC template (barely simplified). I
haven’t but added the dynamic bits, so what we see right here is static
content material, offered for instance:

index.tmpl

  <part class="todoapp">
    <ul class="todo-list">
      <!-- These are right here simply to point out the construction of the listing objects -->
      <!-- Listing objects ought to get the category `accomplished` when marked as accomplished -->
      <li class="accomplished">  
        <div class="view">
          <enter class="toggle" sort="checkbox" checked>
          <label>Style JavaScript</label> 
          <button class="destroy"></button>
        </div>
      </li>
      <li>
        <div class="view">
          <enter class="toggle" sort="checkbox">
          <label>Purchase a unicorn</label> 
          <button class="destroy"></button>
        </div>
      </li>
    </ul>
    <footer class="footer">
      <!-- This must be `0 objects left` by default -->
      <span class="todo-count"><robust>0</robust> merchandise left</span> 
      <ul class="filters">
        <li>
          <a class="chosen" href="#/">All</a> 
        </li>
        <li>
          <a href="#/lively">Energetic</a>
        </li>
        <li>
          <a href="#/accomplished">Accomplished</a>
        </li>
      </ul>
      <!-- Hidden if no accomplished objects are left ↓ -->
      <button class="clear-completed">Clear accomplished</button> 
    </footer>
  </part>  

source

By wanting on the static model of the template, we are able to deduce which
CSS selectors can be utilized to determine the related components for the 5 dynamic
options listed above:

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

We are able to use these selectors to focus our exams on simply the issues we wish to check.

Testing HTML content material

The primary check will search for all of the objects, and show that the info
arrange by the check is rendered accurately.

func Test_todoItemsAreShown(t *testing.T) 
  mannequin := todo.NewList()
  mannequin.Add("Foo")
  mannequin.Add("Bar")

  buf := renderTemplate(mannequin)

  // assert there are two <li> components contained in the <ul class="todo-list"> 
  // assert the primary <li> textual content is "Foo"
  // assert the second <li> textual content is "Bar"

We want a method to question the HTML doc with our CSS selector; a very good
library for Go is goquery, that implements an API impressed by jQuery.
In Java, we maintain utilizing the identical library we used to check for sound HTML, particularly
jsoup. Our check turns into:

Go

  func Test_todoItemsAreShown(t *testing.T) 
    mannequin := todo.NewList()
    mannequin.Add("Foo")
    mannequin.Add("Bar")
  
    buf := renderTemplate("index.tmpl", mannequin)
  
    // parse the HTML with goquery
    doc, err := goquery.NewDocumentFromReader(bytes.NewReader(buf.Bytes()))
    if err != nil 
      // if parsing fails, we cease the check right here with t.FatalF
      t.Fatalf("Error rendering template %s", err)
    
  
    // assert there are two <li> components contained in the <ul class="todo-list">
    choice := doc.Discover("ul.todo-list li")
    assert.Equal(t, 2, choice.Size())
  
    // assert the primary <li> textual content is "Foo"
    assert.Equal(t, "Foo", textual content(choice.Nodes[0]))
  
    // assert the second <li> textual content is "Bar"
    assert.Equal(t, "Bar", textual content(choice.Nodes[1]))
  
  
  func textual content(node *html.Node) string 
    // A bit mess resulting from the truth that goquery has
    // a .Textual content() technique on Choice however not on html.Node
    sel := goquery.SelectionNodes: []*html.Nodenode
    return strings.TrimSpace(sel.Textual content())
  

source

Java

  @Check
  void todoItemsAreShown() throws IOException 
      var mannequin = new TodoList();
      mannequin.add("Foo");
      mannequin.add("Bar");
  
      var html = renderTemplate("/index.tmpl", mannequin);
  
      // parse the HTML with jsoup
      Doc doc = Jsoup.parse(html, "");
  
      // assert there are two <li> components contained in the <ul class="todo-list">
      var choice = doc.choose("ul.todo-list li");
      assertThat(choice).hasSize(2);
  
      // assert the primary <li> textual content is "Foo"
      assertThat(choice.get(0).textual content()).isEqualTo("Foo");
  
      // assert the second <li> textual content is "Bar"
      assertThat(choice.get(1).textual content()).isEqualTo("Bar");
  

source

If we nonetheless have not modified the template to populate the listing from the
mannequin, this check will fail, as a result of the static template
todo objects have completely different textual content:

Go

  --- FAIL: Test_todoItemsAreShown (0.00s)
      index_template_test.go:44: First listing merchandise: need Foo, obtained Style JavaScript
      index_template_test.go:49: Second listing merchandise: need Bar, obtained Purchase a unicorn

Java

  IndexTemplateTest > todoItemsAreShown() FAILED
      org.opentest4j.AssertionFailedError:
      Anticipating:
       <"Style JavaScript">
      to be equal to:
       <"Foo">
      however was not.

We repair it by making the template use the mannequin information:

Go

  <ul class="todo-list">
     vary .Gadgets 
      <li>
        <div class="view">
          <enter class="toggle" sort="checkbox">
          <label> .Title </label>
          <button class="destroy"></button>
        </div>
      </li>
     finish 
  </ul>

source

Java – jmustache

  <ul class="todo-list">
     #allItems 
    <li>
      <div class="view">
        <enter class="toggle" sort="checkbox">
        <label> title </label>
        <button class="destroy"></button>
      </div>
    </li>
     /allItems 
  </ul>

source

Check each content material and soundness on the identical time

Our check works, however it’s a bit verbose, particularly the Go model. If we will have extra
exams, they’ll grow to be repetitive and tough to learn, so we make it extra concise by extracting a helper perform for parsing the html. We additionally take away the
feedback, because the code must be clear sufficient

Go

  func Test_todoItemsAreShown(t *testing.T) 
    mannequin := todo.NewList()
    mannequin.Add("Foo")
    mannequin.Add("Bar")
  
    buf := renderTemplate("index.tmpl", mannequin)
  
    doc := parseHtml(t, buf)
    choice := doc.Discover("ul.todo-list li")
    assert.Equal(t, 2, choice.Size())
    assert.Equal(t, "Foo", textual content(choice.Nodes[0]))
    assert.Equal(t, "Bar", textual content(choice.Nodes[1]))
  
  
  func parseHtml(t *testing.T, buf bytes.Buffer) *goquery.Doc 
    doc, err := goquery.NewDocumentFromReader(bytes.NewReader(buf.Bytes()))
    if err != nil 
      // if parsing fails, we cease the check right here with t.FatalF
      t.Fatalf("Error rendering template %s", err)
    
    return doc
  

Java

  @Check
  void todoItemsAreShown() throws IOException 
      var mannequin = new TodoList();
      mannequin.add("Foo");
      mannequin.add("Bar");
  
      var html = renderTemplate("/index.tmpl", mannequin);
  
      var doc = parseHtml(html);
      var choice = doc.choose("ul.todo-list li");
      assertThat(choice).hasSize(2);
      assertThat(choice.get(0).textual content()).isEqualTo("Foo");
      assertThat(choice.get(1).textual content()).isEqualTo("Bar");
  
  
  non-public static Doc parseHtml(String html) 
      return Jsoup.parse(html, "");
  

A lot better! At the least in my view. Now that we extracted the parseHtml helper, it is
a good suggestion to examine for sound HTML within the helper:

Go

  func parseHtml(t *testing.T, buf bytes.Buffer) *goquery.Doc 
    assertWellFormedHtml(t, buf)
    doc, err := goquery.NewDocumentFromReader(bytes.NewReader(buf.Bytes()))
    if err != nil 
      // if parsing fails, we cease the check right here with t.FatalF
      t.Fatalf("Error rendering template %s", err)
    
    return doc
  

source

Java

  non-public static Doc parseHtml(String html) 
      var parser = Parser.htmlParser().setTrackErrors(10);
      var doc = Jsoup.parse(html, "", parser);
      assertThat(parser.getErrors()).isEmpty();
      return doc;
  

source

And with this, we are able to eliminate the primary check that we wrote, as we at the moment are testing for sound HTML on a regular basis.

The second check

Now we’re in a very good place for testing extra rendering logic. The
second dynamic function in our listing is “Listing objects ought to get the category
accomplished when marked as accomplished”. We are able to write a check for this:

Go

  func Test_completedItemsGetCompletedClass(t *testing.T) 
    mannequin := todo.NewList()
    mannequin.Add("Foo")
    mannequin.AddCompleted("Bar")
  
    buf := renderTemplate("index.tmpl", mannequin)
  
    doc := parseHtml(t, buf)
    choice := doc.Discover("ul.todo-list li.accomplished")
    assert.Equal(t, 1, choice.Dimension())
    assert.Equal(t, "Bar", textual content(choice.Nodes[0]))
  

source

Java

  @Check
  void completedItemsGetCompletedClass() 
      var mannequin = new TodoList();
      mannequin.add("Foo");
      mannequin.addCompleted("Bar");
  
      var html = renderTemplate("/index.tmpl", mannequin);
  
      Doc doc = Jsoup.parse(html, "");
      var choice = doc.choose("ul.todo-list li.accomplished");
      assertThat(choice).hasSize(1);
      assertThat(choice.textual content()).isEqualTo("Bar");
  

source

And this check could be made inexperienced by including this little bit of logic to the
template:

Go

  <ul class="todo-list">
     vary .Gadgets 
      <li class=" if .IsCompleted accomplished finish ">
        <div class="view">
          <enter class="toggle" sort="checkbox">
          <label> .Title </label>
          <button class="destroy"></button>
        </div>
      </li>
     finish 
  </ul>

source

Java – jmustache

  <ul class="todo-list">
     #allItems 
    <li class=" #isCompleted accomplished /isCompleted ">
      <div class="view">
        <enter class="toggle" sort="checkbox">
        <label> title </label>
        <button class="destroy"></button>
      </div>
    </li>
     /allItems 
  </ul>

source

So little by little, we are able to check and add the assorted dynamic options
that our template ought to have.

Make it simple so as to add new exams

The primary of the 20 suggestions from the wonderful talk by Russ Cox on Go
Testing
is “Make it simple so as to add new check instances“. Certainly, in Go there
is a bent to make most exams parameterized, for this very cause.
Then again, whereas Java has
good support
for parameterized tests
with JUnit 5, they aren’t used as a lot.

Since our present two exams have the identical construction, we
may issue them right into a single parameterized check.

A check case for us will include:

  • A reputation (in order that we are able to produce clear error messages when the check
    fails)
  • A mannequin (in our case a todo.Listing)
  • A CSS selector
  • A listing of textual content matches that we look forward to finding after we run the CSS
    selector on the rendered HTML.

So that is the info construction for our check instances:

Go

  var testCases = []struct 
    title     string
    mannequin    *todo.Listing
    selector string
    matches  []string
  
    
      title: "all todo objects are proven",
      mannequin: todo.NewList().
        Add("Foo").
        Add("Bar"),
      selector: "ul.todo-list li",
      matches:  []string"Foo", "Bar",
    ,
    
      title: "accomplished objects get the 'accomplished' class",
      mannequin: todo.NewList().
        Add("Foo").
        AddCompleted("Bar"),
      selector: "ul.todo-list li.accomplished",
      matches:  []string"Bar",
    ,
  

source

Java

  file TestCase(String title,
                  TodoList mannequin,
                  String selector,
                  Listing<String> matches) 
      @Override
      public String toString() 
          return title;
      
  
  
  public static TestCase[] indexTestCases() 
      return new TestCase[]
              new TestCase(
                      "all todo objects are proven",
                      new TodoList()
                              .add("Foo")
                              .add("Bar"),
                      "ul.todo-list li",
                      Listing.of("Foo", "Bar")),
              new TestCase(
                      "accomplished objects get the 'accomplished' class",
                      new TodoList()
                              .add("Foo")
                              .addCompleted("Bar"),
                      "ul.todo-list li.accomplished",
                      Listing.of("Bar")),
      ;
  

source

And that is our parameterized check:

Go

  func Test_indexTemplate(t *testing.T) 
    for _, check := vary testCases 
      t.Run(check.title, func(t *testing.T) 
        buf := renderTemplate("index.tmpl", check.mannequin)
  
        assertWellFormedHtml(t, buf)
        doc := parseHtml(t, buf)
        choice := doc.Discover(check.selector)
        require.Equal(t, len(check.matches), len(choice.Nodes), "surprising # of matches")
        for i, node := vary choice.Nodes 
          assert.Equal(t, check.matches[i], textual content(node))
        
      )
    
  

source

Java

  @ParameterizedTest
  @MethodSource("indexTestCases")
  void testIndexTemplate(TestCase check) 
      var html = renderTemplate("/index.tmpl", check.mannequin);
  
      var doc = parseHtml(html);
      var choice = doc.choose(check.selector);
      assertThat(choice).hasSize(check.matches.dimension());
      for (int i = 0; i < check.matches.dimension(); i++) 
          assertThat(choice.get(i).textual content()).isEqualTo(check.matches.get(i));
      
  

source

We are able to now run our parameterized check and see it move:

Go

  $ go check -v
  === RUN   Test_indexTemplate
  === RUN   Test_indexTemplate/all_todo_items_are_shown
  === RUN   Test_indexTemplate/completed_items_get_the_'accomplished'_class
  --- PASS: Test_indexTemplate (0.00s)
      --- PASS: Test_indexTemplate/all_todo_items_are_shown (0.00s)
      --- PASS: Test_indexTemplate/completed_items_get_the_'accomplished'_class (0.00s)
  PASS
  okay    tdd-html-templates  0.608s

Java

  $ ./gradlew check
  
  > Activity :check
  
  IndexTemplateTest > testIndexTemplate(TestCase) > [1] all todo objects are proven PASSED
  IndexTemplateTest > testIndexTemplate(TestCase) > [2] accomplished objects get the 'accomplished' class PASSED

Be aware how, by giving a reputation to our check instances, we get very readable check output, each on the terminal and within the IDE:

Having rewritten our two outdated exams in desk type, it is now tremendous simple so as to add
one other. That is the check for the “x objects left” textual content:

Go

  
    title: "objects left",
    mannequin: todo.NewList().
      Add("One").
      Add("Two").
      AddCompleted("Three"),
    selector: "span.todo-count",
    matches:  []string"2 objects left",
  ,

source

Java

  new TestCase(
      "objects left",
      new TodoList()
              .add("One")
              .add("Two")
              .addCompleted("Three"),
      "span.todo-count",
      Listing.of("2 objects left")),

source

And the corresponding change within the html template is:

Go

  <span class="todo-count"><robust>len .ActiveItems</robust> objects left</span>

source

Java – jmustache

  <span class="todo-count"><robust>activeItemsCount</robust> objects left</span>

source

The above change within the template requires a supporting technique within the mannequin:

Go

  sort Merchandise struct 
    Title       string
    IsCompleted bool
  
  
  sort Listing struct 
    Gadgets []*Merchandise
  
  
  func (l *Listing) ActiveItems() []*Merchandise 
    var outcome []*Merchandise
    for _, merchandise := vary l.Gadgets 
      if !merchandise.IsCompleted 
        outcome = append(outcome, merchandise)
      
    
    return outcome
  

source

Java

  public class TodoList 
      non-public closing Listing<TodoItem> objects = new ArrayList<>();
      // ...
      public lengthy activeItemsCount() 
          return objects.stream().filter(TodoItem::isActive).rely();
      
  

source

We have invested a bit of effort in our testing infrastructure, in order that including new
check instances is less complicated. Within the subsequent part, we’ll see that the necessities
for the subsequent check instances will push us to refine our check infrastructure additional.

Making the desk extra expressive, on the expense of the check code

We’ll now check the “All”, “Energetic” and “Accomplished” navigation hyperlinks at
the underside of the UI (see the picture above),
and these rely upon which url we’re visiting, which is
one thing that our template has no method to discover out.

At the moment, all we move to our template is our mannequin, which is a todo-list.
It is not right so as to add the at the moment visited url to the mannequin, as a result of that’s
person navigation state, not utility state.

So we have to move extra info to the template past the mannequin. A simple method
is to move a map, which we assemble in our
renderTemplate perform:

Go

  func renderTemplate(mannequin *todo.Listing, path string) bytes.Buffer 
    templ := template.Should(template.ParseFiles("index.tmpl"))
    var buf bytes.Buffer
    information := map[string]any
      "mannequin": mannequin,
      "path":  path,
    
    err := templ.Execute(&buf, information)
    if err != nil 
      panic(err)
    
    return buf
  

Java

  non-public String renderTemplate(String templateName, TodoList mannequin, String path) 
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream(templateName)));
      var information = Map.of(
              "mannequin", mannequin,
              "path", path
      );
      return template.execute(information);
  

And correspondingly our check instances desk has yet one more subject:

Go

  var testCases = []struct 
    title     string
    mannequin    *todo.Listing
    path     string
    selector string
    matches  []string
  
    
      title: "all todo objects are proven",
      mannequin: todo.NewList().
        Add("Foo").
        Add("Bar"),
      selector: "ul.todo-list li",
      matches:  []string"Foo", "Bar",
    ,
  // ... the opposite instances
    
      title:     "highlighted navigation hyperlink: All",
      path:     "/",
      selector: "ul.filters a.chosen",
      matches:  []string"All",
    ,
    
      title:     "highlighted navigation hyperlink: Energetic",
      path:     "/lively",
      selector: "ul.filters a.chosen",
      matches:  []string"Energetic",
    ,
    
      title:     "highlighted navigation hyperlink: Accomplished",
      path:     "/accomplished",
      selector: "ul.filters a.chosen",
      matches:  []string"Accomplished",
    ,
  

Java

  file TestCase(String title,
                  TodoList mannequin,
                  String path,
                  String selector,
                  Listing<String> matches) 
      @Override
      public String toString() 
          return title;
      
  
  
  public static TestCase[] indexTestCases() 
      return new TestCase[]
              new TestCase(
                      "all todo objects are proven",
                      new TodoList()
                              .add("Foo")
                              .add("Bar"),
                      "/",
                      "ul.todo-list li",
                      Listing.of("Foo", "Bar")),
              // ... the earlier instances
              new TestCase(
                      "highlighted navigation hyperlink: All",
                      new TodoList(),
                      "/",
                      "ul.filters a.chosen",
                      Listing.of("All")),
              new TestCase(
                      "highlighted navigation hyperlink: Energetic",
                      new TodoList(),
                      "/lively",
                      "ul.filters a.chosen",
                      Listing.of("Energetic")),
              new TestCase(
                      "highlighted navigation hyperlink: Accomplished",
                      new TodoList(),
                      "/accomplished",
                      "ul.filters a.chosen",
                      Listing.of("Accomplished")),
      ;
  

We discover that for the three new instances, the mannequin is irrelevant;
whereas for the earlier instances, the trail is irrelevant. The Go syntax permits us
to initialize a struct with simply the fields we’re fascinated with, however Java doesn’t have
the same function, so we’re pushed to move further info, and this makes the check instances
desk more durable to grasp.

A developer may have a look at the primary check case and surprise if the anticipated habits relies upon
on the trail being set to "/", and may be tempted so as to add extra instances with
a special path. In the identical method, when studying the
highlighted navigation hyperlink check instances, the developer may surprise if the
anticipated habits is dependent upon the mannequin being set to an empty todo listing. If that’s the case, one may
be led so as to add irrelevant check instances for the highlighted hyperlink with non-empty todo-lists.

We wish to optimize for the time of the builders, so it is worthwhile to keep away from including irrelevant
information to our check case. In Java we would move null for the
irrelevant fields, however there’s a greater method: we are able to use
the builder sample,
popularized by Joshua Bloch.
We are able to shortly write one for the Java TestCase file this manner:

Java

  file TestCase(String title,
                  TodoList mannequin,
                  String path,
                  String selector,
                  Listing<String> matches) 
      @Override
      public String toString() 
          return title;
      
  
      public static closing class Builder 
          String title;
          TodoList mannequin;
          String path;
          String selector;
          Listing<String> matches;
  
          public Builder title(String title) 
              this.title = title;
              return this;
          
  
          public Builder mannequin(TodoList mannequin) 
              this.mannequin = mannequin;
              return this;
          
  
          public Builder path(String path) 
              this.path = path;
              return this;
          
  
          public Builder selector(String selector) 
              this.selector = selector;
              return this;
          
  
          public Builder matches(String ... matches) 
              this.matches = Arrays.asList(matches);
              return this;
          
  
          public TestCase construct() 
              return new TestCase(title, mannequin, path, selector, matches);
          
      
  

Hand-coding builders is a bit of tedious, however doable, although there are
automated ways to jot down them.
Now we are able to rewrite our Java check instances with the Builder, to
obtain higher readability:

Java

  public static TestCase[] indexTestCases() 
      return new TestCase[]
              new TestCase.Builder()
                      .title("all todo objects are proven")
                      .mannequin(new TodoList()
                              .add("Foo")
                              .add("Bar"))
                      .selector("ul.todo-list li")
                      .matches("Foo", "Bar")
                      .construct(),
              // ... different instances
              new TestCase.Builder()
                      .title("highlighted navigation hyperlink: Accomplished")
                      .path("/accomplished")
                      .selector("ul.filters a.chosen")
                      .matches("Accomplished")
                      .construct(),
      ;
  

So, the place are we with our exams? At current, they fail for the flawed cause: null-pointer exceptions
as a result of lacking mannequin and path values.
In an effort to get our new check instances to fail for the precise cause, particularly that the template does
not but have logic to focus on the right hyperlink, we should
present default values for mannequin and path. In Go, we are able to do that
within the check technique:

Go

  func Test_indexTemplate(t *testing.T) 
    for _, check := vary testCases 
      t.Run(check.title, func(t *testing.T) 
        if check.mannequin == nil 
          check.mannequin = todo.NewList()
        
        buf := renderTemplate(check.mannequin, check.path)
        // ... identical as earlier than 
      )
    
  

source

In Java, we are able to present default values within the builder:

Java

  public static closing class Builder 
      String title;
      TodoList mannequin = new TodoList();
      String path = "/";
      String selector;
      Listing<String> matches;
      // ...
  

source

With these modifications, we see that the final two check instances, those for the highlighted hyperlink Energetic
and Accomplished fail, for the anticipated cause that the highlighted hyperlink doesn’t change:

Go

  === RUN   Test_indexTemplate/highlighted_navigation_link:_Active
      index_template_test.go:82: 
            Error Hint:  .../tdd-templates/go/index_template_test.go:82
            Error:        Not equal: 
                          anticipated: "Energetic"
                          precise  : "All"
  === RUN   Test_indexTemplate/highlighted_navigation_link:_Completed
      index_template_test.go:82: 
            Error Hint:  .../tdd-templates/go/index_template_test.go:82
            Error:        Not equal: 
                          anticipated: "Accomplished"
                          precise  : "All"

Java

  IndexTemplateTest > testIndexTemplate(TestCase) > [5] highlighted navigation hyperlink: Energetic FAILED
      org.opentest4j.AssertionFailedError:
      Anticipating:
       <"All">
      to be equal to:
       <"Energetic">
      however was not.
  
  IndexTemplateTest > testIndexTemplate(TestCase) > [6] highlighted navigation hyperlink: Accomplished FAILED
      org.opentest4j.AssertionFailedError:
      Anticipating:
       <"All">
      to be equal to:
       <"Accomplished">
      however was not.

To make the exams move, we make these modifications to the template:

Go

  <ul class="filters">
    <li>
      <a class=" if eq .path "/" chosen finish " href="#/">All</a>
    </li>
    <li>
      <a class=" if eq .path "/lively" chosen finish " href="#/lively">Energetic</a>
    </li>
    <li>
      <a class=" if eq .path "/accomplished" chosen finish " href="#/accomplished">Accomplished</a>
    </li>
  </ul>

source

Java – jmustache

  <ul class="filters">
    <li>
      <a class=" #pathRoot chosen /pathRoot " href="#/">All</a>
    </li>
    <li>
      <a class=" #pathActive chosen /pathActive " href="#/lively">Energetic</a>
    </li>
    <li>
      <a class=" #pathCompleted chosen /pathCompleted " href="#/accomplished">Accomplished</a>
    </li>
  </ul>

source

Because the Mustache template language doesn’t enable for equality testing, we should change the
information handed to the template in order that we execute the equality exams earlier than rendering the template:

Java

  non-public String renderTemplate(String templateName, TodoList mannequin, String path) 
      var template = Mustache.compiler().compile(
              new InputStreamReader(
                      getClass().getResourceAsStream(templateName)));
      var information = Map.of(
              "mannequin", mannequin,
              "pathRoot", path.equals("/"),
              "pathActive", path.equals("/lively"),
              "pathCompleted", path.equals("/accomplished")
      );
      return template.execute(information);
  

source

And with these modifications, all of our exams now move.

To recap this part, we made the check code a bit of bit extra difficult, in order that the check
instances are clearer: this can be a excellent tradeoff!

Degree 3: testing HTML behaviour

Within the story thus far, we examined the behaviour of the HTML
templates
, by checking the construction of the generated HTML.
That is good, however what if we wished to check the behaviour of the HTML
itself, plus any CSS and JavaScript it could use?

The behaviour of HTML by itself is normally fairly apparent, as a result of
there may be not a lot of it. The one components that may work together with the
person are the anchor (<a>), <type> and
<enter> components, however the image modifications utterly when
we add CSS, that may conceal, present, transfer round issues and much extra, and
with JavaScript, that may add any behaviour to a web page.

In an utility that’s primarily rendered server-side, we anticipate
that the majority behaviour is applied by returning new HTML with a
round-trip to the person, and this may be examined adequately with the
strategies we have seen thus far, however what if we wished to hurry up the
utility behaviour with a library comparable to HTMX? This library works via particular
attributes which are added to components so as to add Ajax behaviour. These
attributes are in impact a DSL that we would wish to
check.

How can we check the mix of HTML, CSS and JavaScript in
a unit check?

Testing HTML, CSS and JavaScript requires one thing that is ready to
interpret and execute their behaviours; in different phrases, we’d like a
browser! It’s customary to make use of headless browsers in end-to-end exams;
can we use them for unitary exams as an alternative? I believe that is doable,
utilizing the next strategies, though I have to admit I’ve but to strive
this on an actual undertaking.

We’ll use the Playwright
library, that’s out there for each Go and
Java. The exams we
are going to jot down can be slower, as a result of we must wait just a few
seconds for the headless browser to start out, however will retain among the
vital traits of unit exams, primarily that we’re testing
simply the HTML (and any related CSS and JavaScript), in isolation from
some other server-side logic.

Persevering with with the TodoMVC
instance, the subsequent factor we would wish to check is what occurs when the
person clicks on the checkbox of a todo merchandise. What we might wish to occur is
that:

  1. A POST name to the server is made, in order that the appliance is aware of
    that the state of a todo merchandise has modified
  2. The server returns new HTML for the dynamic a part of the web page,
    particularly the entire part with class “todoapp”, in order that we are able to present the
    new state of the appliance together with the rely of remaining “lively”
    objects (see the template above)
  3. The web page replaces the outdated contents of the “todoapp” part with
    the brand new ones.

Loading the web page within the Playwright browser

We begin with a check that can simply load the preliminary HTML. The check
is a bit of concerned, so I present the entire code right here, after which I’ll
remark it little by little.

Go

  func Test_toggleTodoItem(t *testing.T) 
    // render the preliminary HTML
    mannequin := todo.NewList().
      Add("One").
      Add("Two")
    initialHtml := renderTemplate("index.tmpl", mannequin, "/")
  
    // open the browser web page with Playwright
    web page := openPage()
    defer web page.Shut()
    logActivity(web page)
  
    // stub community calls
    err := web page.Route("**", func(route playwright.Route) 
      if route.Request().URL() == "http://localhost:4567/index.html" 
        // serve the preliminary HTML
        stubResponse(route, initialHtml.String(), "textual content/html")
       else 
        // keep away from surprising requests
        panic("surprising request: " + route.Request().URL())
      
    )
    if err != nil 
      t.Deadly(err)
    
  
    // load preliminary HTML within the web page
    response, err := web page.Goto("http://localhost:4567/index.html")
    if err != nil 
      t.Deadly(err)
    
    if response.Standing() != 200 
      t.Fatalf("surprising standing: %d", response.Standing())
    
  

source

Java

  public class IndexBehaviourTest {
      static Playwright playwright;
      static Browser browser;
  
      @BeforeAll
      static void launchBrowser() 
          playwright = Playwright.create();
          browser = playwright.chromium().launch();
      
  
      @AfterAll
      static void closeBrowser() 
          playwright.shut();
      
  
      @Check
      void toggleTodoItem() 
          // Render the preliminary html
          TodoList mannequin = new TodoList()
                  .add("One")
                  .add("Two");
          String initialHtml = renderTemplate("/index.tmpl", mannequin, "/");
          
          strive (Web page web page = browser.newPage()) 
              logActivity(web page);
  
              // stub community calls
              web page.route("**", route -> 
                  if (route.request().url().equals("http://localhost:4567/index.html")) 
                      // serve the preliminary HTML
                      route.fulfill(new Route.FulfillOptions()
                              .setContentType("textual content/html")
                              .setBody(initialHtml));
                   else 
                      // we do not need surprising calls
                      fail(String.format("Sudden request: %s %s", route.request().technique(), route.request().url()));
                  
              );
          
              // load preliminary html
              web page.navigate("http://localhost:4567/index.html");
          
      
  }

source

In the beginning of the check, we initialize the mannequin with two todo
objects “One” and “Two”, then we render the template as earlier than:

Go

  mannequin := todo.NewList().
    Add("One").
    Add("Two")
  initialHtml := renderTemplate("index.tmpl", mannequin, "/")

Java

  TodoList mannequin = new TodoList()
          .add("One")
          .add("Two");
  String initialHtml = renderTemplate("/index.tmpl", mannequin, "/");

Then we open the Playwright “web page”, which can begin a headless
browser

Go

  web page := openPage()
  defer web page.Shut()
  logActivity(web page)

Java

  strive (Web page web page = browser.newPage()) 
      logActivity(web page);

The openPage perform in Go returns a Playwright
Web page object,

Go

  func openPage() playwright.Web page 
    pw, err := playwright.Run()
    if err != nil 
      log.Fatalf("couldn't begin playwright: %v", err)
    
    browser, err := pw.Chromium.Launch()
    if err != nil 
      log.Fatalf("couldn't launch browser: %v", err)
    
    web page, err := browser.NewPage()
    if err != nil 
      log.Fatalf("couldn't create web page: %v", err)
    
    return web page
  

and the logActivity perform supplies suggestions on what
the web page is doing

Go

  func logActivity(web page playwright.Web page) 
    web page.OnRequest(func(request playwright.Request) 
      log.Printf(">> %s %sn", request.Methodology(), request.URL())
    )
    web page.OnResponse(func(response playwright.Response) 
      log.Printf("<< %d %sn", response.Standing(), response.URL())
    )
    web page.OnLoad(func(web page playwright.Web page) 
      log.Println("Loaded: " + web page.URL())
    )
    web page.OnConsole(func(message playwright.ConsoleMessage) 
      log.Println("!  " + message.Textual content())
    )
  

Java

  non-public void logActivity(Web page web page) 
      web page.onRequest(request -> System.out.printf(">> %s %spercentn", request.technique(), request.url()));
      web page.onResponse(response -> System.out.printf("<< %s %spercentn", response.standing(), response.url()));
      web page.onLoad(page1 -> System.out.println("Loaded: " + page1.url()));
      web page.onConsoleMessage(consoleMessage -> System.out.println("!  " + consoleMessage.textual content()));
  

Then we stub all community exercise that the web page may attempt to do

Go

  err := web page.Route("**", func(route playwright.Route) 
    if route.Request().URL() == "http://localhost:4567/index.html" 
      // serve the preliminary HTML
      stubResponse(route, initialHtml.String(), "textual content/html")
     else 
      // keep away from surprising requests
      panic("surprising request: " + route.Request().URL())
    
  )

Java

  // stub community calls
  web page.route("**", route -> 
      if (route.request().url().equals("http://localhost:4567/index.html")) 
          // serve the preliminary HTML
          route.fulfill(new Route.FulfillOptions()
                  .setContentType("textual content/html")
                  .setBody(initialHtml));
       else 
          // we do not need surprising calls
          fail(String.format("Sudden request: %s %s", route.request().technique(), route.request().url()));
      
  );

and we ask the web page to load the preliminary HTML

Go

  response, err := web page.Goto("http://localhost:4567/index.html")

Java

  web page.navigate("http://localhost:4567/index.html");

With all this equipment in place, we run the check; it succeeds and
it logs the stubbed community exercise on commonplace output:

Go

  === RUN   Test_toggleTodoItem
  >> GET http://localhost:4567/index.html
  << 200 http://localhost:4567/index.html
  Loaded: http://localhost:4567/index.html
  --- PASS: Test_toggleTodoItem (0.89s)

Java

  IndexBehaviourTest > toggleTodoItem() STANDARD_OUT
      >> GET http://localhost:4567/index.html
      << 200 http://localhost:4567/index.html
      Loaded: http://localhost:4567/index.html
  
  IndexBehaviourTest > toggleTodoItem() PASSED

So with this check we at the moment are in a position to load arbitrary HTML in a
headless browser. Within the subsequent sections we’ll see the way to simulate person
interplay with components of the web page, and observe the web page’s
behaviour. However first we have to clear up an issue with the dearth of
identifiers in our area mannequin.

Figuring out todo objects

Now we wish to click on on the “One” checkbox. The issue we now have is
that at current, we now have no method to determine particular person todo objects, so
we introduce an Id subject within the todo merchandise:

Go – up to date mannequin with Id

  sort Merchandise struct 
    Id          int
    Title       string
    IsCompleted bool
  
  
  func (l *Listing) AddWithId(id int, title string) *Listing 
    merchandise := Merchandise
      Id:    id,
      Title: title,
    
    l.Gadgets = append(l.Gadgets, &merchandise)
    return l
  
  
  // Add creates a brand new todo.Merchandise with a random Id
  func (l *Listing) Add(title string) *Listing 
    merchandise := Merchandise
      Id:    generateRandomId(),
      Title: title,
    
    l.Gadgets = append(l.Gadgets, &merchandise)
    return l
  
  
  func generateRandomId() int 
    return abs(rand.Int())
  

Java – up to date mannequin with Id

  public class TodoList 
      non-public closing Listing<TodoItem> objects = new ArrayList<>();
  
      public TodoList add(String title) 
          objects.add(new TodoItem(generateRandomId(), title, false));
          return this;
      
  
      public TodoList addCompleted(String title) 
          objects.add(new TodoItem(generateRandomId(), title, true));
          return this;
      
  
      public TodoList add(int id, String title) 
          objects.add(new TodoItem(id, title, false));
          return this;
      
  
      non-public static int generateRandomId() 
          return new Random().nextInt(0, Integer.MAX_VALUE);
      
  
  
  public file TodoItem(int id, String title, boolean isCompleted) 
      public boolean isActive() 
          return !isCompleted;
      
  

And we replace the mannequin in our check so as to add express Ids

Go – including Id within the check information

  func Test_toggleTodoItem(t *testing.T) 
    // render the preliminary HTML
    mannequin := todo.NewList().
      AddWithId(101, "One").
      AddWithId(102, "Two")
    initialHtml := renderTemplate("index.tmpl", mannequin, "/")
    // ... 
  

Java – including Id within the check information

  @Check
  void toggleTodoItem() 
      // Render the preliminary html
      TodoList mannequin = new TodoList()
              .add(101, "One")
              .add(102, "Two");
      String initialHtml = renderTemplate("/index.tmpl", mannequin, "/");
  

We at the moment are prepared to check person interplay with the web page.

Clicking on a todo merchandise

We wish to simulate person interplay with the HTML web page. It may be
tempting to proceed to make use of CSS selectors to determine the particular
checkbox that we wish to click on, however there’s a greater method: there’s a
consensus amongst front-end builders that the easiest way to check
interplay with a web page is to use it
the same way that users do
. For example, you do not search for a
button via a CSS locator comparable to button.purchase; as an alternative,
you search for one thing clickable with the label “Purchase”. In follow,
this implies figuring out components of the web page via their
ARIA
roles.

To this finish, we add code to our check to search for a checkbox labelled
“One”:

Go

  func Test_toggleTodoItem(t *testing.T) 
    // ...
    // click on on the "One" checkbox
    checkbox := web page.GetByRole(*playwright.AriaRoleCheckbox, playwright.PageGetByRoleOptionsIdentify: "One")
    if err := checkbox.Click on(); err != nil 
      t.Deadly(err)
    
  

Java

  @Check
  void toggleTodoItem() 
          // ...
          // click on on the "One" checkbox
          var checkbox = web page.getByRole(AriaRole.CHECKBOX, new Web page.GetByRoleOptions().setName("One"));
          checkbox.click on();
      
  

We run the check, and it fails:

Go

  >> GET http://localhost:4567/index.html
  << 200 http://localhost:4567/index.html
  Loaded: http://localhost:4567/index.html
  --- FAIL: Test_toggleTodoItem (32.74s)
      index_behaviour_test.go:50: playwright: timeout: Timeout 30000ms exceeded.

Java

  IndexBehaviourTest > toggleTodoItem() STANDARD_OUT
      >> GET http://localhost:4567/index.html
      << 200 http://localhost:4567/index.html
      Loaded: http://localhost:4567/index.html
  
  IndexBehaviourTest > toggleTodoItem() FAILED
      com.microsoft.playwright.TimeoutError: Error 
        message="hyperlink the label to the checkbox correctly:

generated HTML with dangerous accessibility

  <li>
    <div class="view">
      <enter class="toggle" sort="checkbox">
      <label>One</label>
      <button class="destroy"></button>
    </div>
  </li>

We repair it by utilizing the for attribute within the
template,

index.tmpl – Go

  <li>
    <div class="view">
      <enter id="checkbox-.Id" class="toggle" sort="checkbox">
      <label for="checkbox-.Id">.Title</label>
      <button class="destroy"></button>
    </div>
  </li>

index.tmpl – Java

  <li>
    <div class="view">
      <enter id="checkbox- id " class="toggle" sort="checkbox">
      <label for="checkbox- id "> title </label>
      <button class="destroy"></button>
    </div>
  </li>

In order that it generates correct, accessible HTML:

generated HTML with higher accessibility

  <li>
    <div class="view">
      <enter id="checkbox-101" class="toggle" sort="checkbox">
      <label for="checkbox-101">One</label>
      <button class="destroy"></button>
    </div>
  </li>

We run once more the check, and it passes.

On this part we noticed how testing the HTML in the identical was as customers
work together with it led us to make use of ARIA roles, which led to bettering
accessibility of our generated HTML. Within the subsequent part, we'll see
the way to check that the clicking on a todo merchandise triggers a distant name to the
server, that ought to lead to swapping part of the present HTML with
the HTML returned by the XHR name.

Spherical-trip to the server

Now we’ll prolong our check. We inform the check that if name to
POST /toggle/101 is acquired, it ought to return some
stubbed HTML.

Go

   else if route.Request().URL() == "http://localhost:4567/toggle/101" && route.Request().Methodology() == "POST" 
    // we anticipate {that a} POST /toggle/101 request is made after we click on on the "One" checkbox
    const stubbedHtml = `
      <part class="todoapp">
        <p>Stubbed html</p>
      </part>`
    stubResponse(route, stubbedHtml, "textual content/html")

Java

   else if (route.request().url().equals("http://localhost:4567/toggle/101") && route.request().technique().equals("POST")) 
      // we anticipate {that a} POST /toggle/101 request is made after we click on on the "One" checkbox
      String stubbedHtml = """
          <part class="todoapp">
              <p>Stubbed html</p>
          </part>
          """;
      route.fulfill(new Route.FulfillOptions()
              .setContentType("textual content/html")
              .setBody(stubbedHtml));

And we stub the loading of the HTMX library, which we load from a
native file:

Go

   else if route.Request().URL() == "https://unpkg.com/[email protected]" 
    // serve the htmx library
    stubResponse(route, readFile("testdata/htmx.min.js"), "utility/javascript")

Go

   else if (route.request().url().equals("https://unpkg.com/[email protected]")) {
      // serve the htmx library
      route.fulfill(new Route.FulfillOptions()
              .setContentType("textual content/html")
              .setBody(readFile("/htmx.min.js")));

Lastly, we add the expectation that, after we click on the checkbox,
the part of the HTML that accommodates a lot of the utility is
reloaded.

Go

  // click on on the "One" checkbox
  checkbox := web page.GetByRole(*playwright.AriaRoleCheckbox, playwright.PageGetByRoleOptionsName: "One")
  if err := checkbox.Click on(); err != nil 
    t.Deadly(err)
  

  // examine that the web page has been up to date
  doc := parseHtml(t, content material(t, web page))
  components := doc.Discover("physique > part.todoapp > p")
  assert.Equal(t, "Stubbed html", components.Textual content(), should(web page.Content material()))

java

  // click on on the "One" checkbox
  var checkbox = web page.getByRole(AriaRole.CHECKBOX, new Web page.GetByRoleOptions().setName("One"));
  checkbox.click on();

  // examine that the web page has been up to date
  var doc = parseHtml(web page.content material());
  var components = doc.choose("physique > part.todoapp > p");
  assertThat(components.textual content())
          .describedAs(web page.content material())
          .isEqualTo("Stubbed html");

We run the check, and it fails, as anticipated. In an effort to perceive
why precisely it fails, we add to the error message the entire HTML
doc.

Go

  assert.Equal(t, "Stubbed html", components.Textual content(), should(web page.Content material()))

Java

  assertThat(components.textual content())
          .describedAs(web page.content material())
          .isEqualTo("Stubbed html");

The error message may be very verbose, however we see that the explanation it
fails is that we do not see the stubbed HTML within the output. This implies
that the web page didn’t make the anticipated XHR name.

Go – Java is comparable

  --- FAIL: Test_toggleTodoItem (2.75s)
  === RUN   Test_toggleTodoItem
  >> GET http://localhost:4567/index.html
  << 200 http://localhost:4567/index.html
  Loaded: http://localhost:4567/index.html
      index_behaviour_test.go:67:
            Error Hint:  .../index_behaviour_test.go:67
            Error:        Not equal:
                          anticipated: "Stubbed html"
                          precise  : ""
                          ...
            Check:         Test_toggleTodoItem
            Messages:     <!DOCTYPE html><html lang="en"><head>
                              <meta charset="utf-8">
                              <meta title="viewport" content material="width=device-width, initial-scale=1">
                              <title>Template • TodoMVC</title>
                              <script src="https://unpkg.com/[email protected]"></script>
                            <physique>
                              <part class="todoapp">
                          ...
                                    <li class="">
                                      <div class="view">
                                        <enter id="checkbox-101" class="toggle" sort="checkbox">
                                        <label for="checkbox-101">One</label>
                                        <button class="destroy"></button>
                                      </div>
                                    </li>
                          ...

We are able to make this check move by altering the HTML template to make use of HTMX
to make an XHR name again to the server. First we load the HTMX
library:

index.tmpl

  <title>Template • TodoMVC</title>
  <script src="https://unpkg.com/[email protected]"></script>

Then we add the HTMX attributes to the checkboxes:

index.tmpl

  <enter
      data-hx-post="/toggle/.Id"
      data-hx-target="part.todoapp"
      id="checkbox-.Id"
      class="toggle"
      sort="checkbox">

The data-hx-post annotation will make HTMX do a POST
name to the desired url. The data-hx-target tells HTMX
to repeat the HTML returned by the decision, to the component specified by the
part.todoapp CSS locator.

We run once more the check, and it nonetheless fails!

Go – Java is comparable

  --- FAIL: Test_toggleTodoItem (2.40s)
  === RUN   Test_toggleTodoItem
  >> GET http://localhost:4567/index.html
  << 200 http://localhost:4567/index.html
  >> GET https://unpkg.com/[email protected]
  << 200 https://unpkg.com/[email protected]
  Loaded: http://localhost:4567/index.html
  >> POST http://localhost:4567/toggle/101
  << 200 http://localhost:4567/toggle/101
      index_behaviour_test.go:67:
            Error Hint:  .../index_behaviour_test.go:67
            Error:        Not equal:
                          anticipated: "Stubbed html"
                          precise  : ""
                          ...
            Check:         Test_toggleTodoItem
            Messages:     <!DOCTYPE html><html lang="en"><head>
                              <meta charset="utf-8">
                              <meta title="viewport" content material="width=device-width, initial-scale=1">
                              <title>Template • TodoMVC</title>
                              <script src="https://unpkg.com/[email protected]"></script>
                          ...
                            <physique>
                              <part class="todoapp"><part class="todoapp">
                                    <p>Stubbed html</p>
                                  </part></part>
                          ...
                          </physique></html>

The log traces present that the POST name occurred as anticipated, however
examination of the error message exhibits that the HTML construction we
anticipated is just not there: we now have a part.todoapp nested
inside one other. Because of this we’re not utilizing the HTMX annotations
accurately, and exhibits why this sort of check could be useful. We add the
lacking annotation

index.tmpl

  <enter
      data-hx-post="/toggle/.Id"
      data-hx-target="part.todoapp"
      data-hx-swap="outerHTML"
      id="checkbox-.Id"
      class="toggle"
      sort="checkbox">

The default behaviour of HTMX is to switch the interior HTML of the
goal component. The data-hx-swap="outerHTML" annotation
tells HTMX to switch the outer HTML as an alternative.

and we check once more, and this time it passes!

Go

  === RUN   Test_toggleTodoItem
  >> GET http://localhost:4567/index.html
  << 200 http://localhost:4567/index.html
  >> GET https://unpkg.com/[email protected]
  << 200 https://unpkg.com/[email protected]
  Loaded: http://localhost:4567/index.html
  >> POST http://localhost:4567/toggle/101
  << 200 http://localhost:4567/toggle/101
  --- PASS: Test_toggleTodoItem (1.39s)

Java

  IndexBehaviourTest > toggleTodoItem() STANDARD_OUT
      >> GET http://localhost:4567/index.html
      << 200 http://localhost:4567/index.html
      >> GET https://unpkg.com/[email protected]
      << 200 https://unpkg.com/[email protected]
      Loaded: http://localhost:4567/index.html
      >> POST http://localhost:4567/toggle/101
      << 200 http://localhost:4567/toggle/101
  
  IndexBehaviourTest > toggleTodoItem() PASSED

On this part we noticed the way to write a check for the behaviour of our
HTML that, whereas utilizing the difficult equipment of a headless browser,
nonetheless feels extra like a unit check than an integration check. It’s in
truth testing simply an HTML web page with any related CSS and JavaScript,
in isolation from different components of the appliance comparable to controllers,
providers or repositories.

The check prices 2-3 seconds of ready time for the headless browser to return up, which is normally an excessive amount of for a unit check; nonetheless, like a unit check, it is vitally secure, as it isn’t flaky, and its failures are documented with a comparatively clear error message.

See the ultimate model of the check in Go and in Java.

Bonus degree: Stringly asserted

Esko Luontola, TDD professional and creator of the net course tdd.mooc.fi, suggested an alternative to testing HTML with CSS selectors: the thought is to rework HTML right into a human-readable canonical type.

Let’s take for instance this snippet of generated HTML:

<ul class="todo-list">
  <li class="">
    <div class="view">
      <enter id="checkbox-100" class="toggle" sort="checkbox">
      <label for="checkbox-100">One</label>
      <button class="destroy"></button>
    </div>
  </li>
  <li class="">
    <div class="view">
      <enter id="checkbox-200" class="toggle" sort="checkbox">
      <label for="checkbox-200">Two</label>
      <button class="destroy"></button>
    </div>
  </li>
  <li class="accomplished">
    <div class="view">
      <enter id="checkbox-300" class="toggle" sort="checkbox">
      <label for="checkbox-300">Three</label>
      <button class="destroy"></button>
    </div>
  </li>
</ul>

We may visualize the above HTML by:

  1. deleting all HTML tags
  2. lowering each sequence of whitespace characters to a single clean

to reach at:

One Two Three

This, nonetheless, removes an excessive amount of of the HTML construction to be helpful. For example, it doesn’t allow us to distinguish between lively and accomplished objects. Some HTML component symbolize seen content material: as an example

<enter worth="foo" />

exhibits a textual content field with the phrase “foo” that is a vital a part of the method we understand HTML. To visualise these components, Esko suggests so as to add a data-test-icon attribute that provides some textual content for use rather than the component when visualizing it for testing. With this,

<enter worth="foo" data-test-icon="[foo]" />

the enter component is visualized as [foo], with the sq. brackets hinting that the phrase “foo” sits inside an editable textual content field. Now if we add test-icons to our HTML template,

Go — Java is comparable

  <ul class="todo-list">
       vary .mannequin.AllItems 
      <li class=" if .IsCompleted accomplished finish ">
          <div class="view">
              <enter data-hx-post="/toggle/ .Id "
                     data-hx-target="part.todoapp"
                     data-hx-swap="outerHTML"
                     id="checkbox- .Id "
                     class="toggle"
                     sort="checkbox"
                     data-test-icon=" if .IsCompleted ✅ else ⬜ finish ">
              <label for="checkbox- .Id "> .Title </label>
              <button class="destroy" data-test-icon="❌️"></button>
          </div>
      </li>
      { finish }
  </ul>

we are able to assert in opposition to its canonical visible illustration like this:

Go

  func Test_visualize_html_example(t *testing.T) 
    mannequin := todo.NewList().
      Add("One").
      Add("Two").
      AddCompleted("Three")
  
    buf := renderTemplate("todo-list.tmpl", mannequin, "/")
  
    anticipated := `
      ⬜ One ❌️
      ⬜ Two ❌️
      ✅ Three ❌️
      `
    assert.Equal(t, normalizeWhitespace(anticipated), visualizeHtml(buf.String()))
  

Java

  @Check
  void visualize_html_example() 
      var mannequin = new TodoList()
              .add("One")
              .add("Two")
              .addCompleted("Three");
  
      var html = renderTemplate("/todo-list.tmpl", mannequin, "/");
  
      assertThat(visualizeHtml(html))
              .isEqualTo(normalizeWhitespace("""
                      ⬜ One ❌️
                      ⬜ Two ❌️
                      ✅ Three ❌️
                      """));
  

Right here is Esko Luontola’s Java implementation of the 2 features that make this doable, and my translation to Go of his code.

Go

  func visualizeHtml(html string) string huge
  
  func normalizeWhitespace(s string) string 
    return strings.TrimSpace(replaceAll(s, "s+", " "))
  
  
  func replaceAll(src, regex, repl string) string 
    re := regexp.MustCompile(regex)
    return re.ReplaceAllString(src, repl)
  

source

Java

  public static String visualizeHtml(String html) code
  
  public static String normalizeWhitespace(String s) 
     return s.replaceAll("s+", " ").trim();
  

source

On this part, we now have seen a way for asserting HTML content material that’s an alternative choice to the CSS selector-based approach utilized in the remainder of the article. Esko Luontola has reported nice success with it, and I hope readers have success with it too!

This method of asserting in opposition to giant, difficult information buildings comparable to HTML pages by lowering them to a canonical string model has no title that I do know of. Martin Fowler suggested “stringly asserted”, and from his suggestion comes the title of this part.