Check-Driving HTML Templates

What else ought to we take a look at?

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

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

What we’d like
is a method to say 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 enables 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 ingredient 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 presupposed to generate appears 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 fashion 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” will probably be
   highlighted, relying on the present url; for example if we determine that the
   url that reveals solely the “Energetic” objects is /lively, then when the present url
   is /lively, the “Energetic” button ought to be surrounded by a skinny pink
   rectangle
5. The “Clear accomplished” button ought to solely be seen if any merchandise is
   accomplished

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

This can be 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, supplied for instance:

index.tmpl

  <part class="todoapp">
    <ul class="todo-list">
      <!-- These are right here simply to indicate the construction of the record objects -->
      <!-- Checklist objects ought to get the category `accomplished` when marked as accomplished -->
      <li class="accomplished">  ②
        <div class="view">
          <enter class="toggle" kind="checkbox" checked>
          <label>Style JavaScript</label> ①
          <button class="destroy"></button>
        </div>
      </li>
      <li>
        <div class="view">
          <enter class="toggle" kind="checkbox">
          <label>Purchase a unicorn</label> ①
          <button class="destroy"></button>
        </div>
      </li>
    </ul>
    <footer class="footer">
      <!-- This ought to be `0 objects left` by default -->
      <span class="todo-count"><robust>0</robust> merchandise left</span> ⓷
      <ul class="filters">
        <li>
          <a class="chosen" href="#/">All</a> ④
        </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> ⑤
    </footer>
  </part>  

source

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

We are able to use these selectors to focus our assessments on simply the issues we wish to take a look at.

Testing HTML content material

The primary take a look at will search for all of the objects, and show that the info
arrange by the take a look at is rendered appropriately.

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 strategy 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 preserve utilizing the identical library we used to check for sound HTML, particularly
jsoup. Our take a look at 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 take a look at 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 {
    // Somewhat mess attributable to the truth that goquery has
    // a .Textual content() methodology on Choice however not on html.Node
    sel := goquery.Choice{Nodes: []*html.Node{node}}
    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 record from the
mannequin, this take a look at 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 record merchandise: need Foo, received Style JavaScript
      index_template_test.go:49: Second record merchandise: need Bar, received 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" kind="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" kind="checkbox">
        <label>{{ title }}</label>
        <button class="destroy"></button>
      </div>
    </li>
    {{ /allItems }}
  </ul>

source

Check each content material and soundness on the identical time

Our take a look at works, however it’s a bit verbose, particularly the Go model. If we will have extra
assessments, they may grow to be repetitive and troublesome to learn, so we make it extra concise by extracting a helper operate for parsing the html. We additionally take away the
feedback, because the code ought to 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 take a look at 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! No less than in my view. Now that we extracted the parseHtml helper, it is
a good suggestion to verify 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 take a look at 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 will eliminate the primary take a look at that we wrote, as we are actually testing for sound HTML on a regular basis.

The second take a look at

Now we’re in a very good place for testing extra rendering logic. The
second dynamic function in our record is “Checklist objects ought to get the category
accomplished when marked as accomplished”. We are able to write a take a look at 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 take a look at will 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" kind="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" kind="checkbox">
        <label>{{ title }}</label>
        <button class="destroy"></button>
      </div>
    </li>
    {{ /allItems }}
  </ul>

source

So little by little, we will take a look at and add the varied dynamic options
that our template ought to have.

Make it simple so as to add new assessments

The primary of the 20 suggestions from the superb talk by Russ Cox on Go
Testing is “Make it simple so as to add new take a look at circumstances“. Certainly, in Go there
is an inclination to make most assessments parameterized, for this very motive.
Alternatively, whereas Java has
good support
for parameterized tests with JUnit 5, they aren’t used as a lot.

Since our present two assessments have the identical construction, we
may issue them right into a single parameterized take a look at.

A take a look at case for us will include:

• A reputation (in order that we will produce clear error messages when the take a look at
  fails)
• A mannequin (in our case a todo.Checklist)
• A CSS selector
• An inventory of textual content matches that we anticipate finding after we run the CSS
  selector on the rendered HTML.

So that is the info construction for our take a look at circumstances:

Go

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

source

Java

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

source

And that is our parameterized take a look at:

Go

  func Test_indexTemplate(t *testing.T) {
    for _, take a look at := vary testCases {
      t.Run(take a look at.identify, func(t *testing.T) {
        buf := renderTemplate("index.tmpl", take a look at.mannequin)
  
        assertWellFormedHtml(t, buf)
        doc := parseHtml(t, buf)
        choice := doc.Discover(take a look at.selector)
        require.Equal(t, len(take a look at.matches), len(choice.Nodes), "sudden # of matches")
        for i, node := vary choice.Nodes {
          assert.Equal(t, take a look at.matches[i], textual content(node))
        }
      })
    }
  }

source

Java

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

source

We are able to now run our parameterized take a look at and see it cross:

Go

  $ go take a look at -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 take a look at
  
  > Process :take a look at
  
  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 take a look at circumstances, we get very readable take a look at output, each on the terminal and within the IDE:

Having rewritten our two outdated assessments in desk kind, it is now tremendous simple so as to add
one other. That is the take a look at for the “x objects left” textual content:

Go

  {
    identify: "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",
      Checklist.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 methodology within the mannequin:

Go

  kind Merchandise struct {
    Title       string
    IsCompleted bool
  }
  
  kind Checklist struct {
    Gadgets []*Merchandise
  }
  
  func (l *Checklist) ActiveItems() []*Merchandise {
    var consequence []*Merchandise
    for _, merchandise := vary l.Gadgets {
      if !merchandise.IsCompleted {
        consequence = append(consequence, merchandise)
      }
    }
    return consequence
  }

source

Java

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

source

We have invested just a little effort in our testing infrastructure, in order that including new
take a look at circumstances is less complicated. Within the subsequent part, we’ll see that the necessities
for the following take a look at circumstances will push us to refine our take a look at infrastructure additional.

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

We’ll now take a look at 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 strategy to discover out.

At present, all we cross to our template is our mannequin, which is a todo-list.
It isn’t appropriate 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 cross extra data to the template past the mannequin. A simple manner
is to cross a map, which we assemble in our
renderTemplate operate:

Go

  func renderTemplate(mannequin *todo.Checklist, 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 take a look at circumstances desk has yet one more discipline:

Go

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

Java

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

We discover that for the three new circumstances, the mannequin is irrelevant;
whereas for the earlier circumstances, the trail is irrelevant. The Go syntax permits us
to initialize a struct with simply the fields we’re keen on, however Java doesn’t have
an identical function, so we’re pushed to cross additional data, and this makes the take a look at circumstances
desk tougher to know.

A developer would possibly have a look at the primary take a look at case and surprise if the anticipated conduct relies upon
on the trail being set to “/”, and is likely to be tempted so as to add extra circumstances with
a special path. In the identical manner, when studying the
highlighted navigation hyperlink take a look at circumstances, the developer would possibly surprise if the
anticipated conduct relies on the mannequin being set to an empty todo record. If that’s the case, one would possibly
be led so as to add irrelevant take a look at circumstances 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 take a look at case. In Java we would cross null for the
irrelevant fields, however there’s a greater manner: we will use
the builder pattern,
popularized by Joshua Bloch.
We are able to rapidly write one for the Java TestCase report this fashion:

Java

  report TestCase(String identify,
                  TodoList mannequin,
                  String path,
                  String selector,
                  Checklist<String> matches) {
      @Override
      public String toString() {
          return identify;
      }
  
      public static remaining class Builder {
          String identify;
          TodoList mannequin;
          String path;
          String selector;
          Checklist<String> matches;
  
          public Builder identify(String identify) {
              this.identify = identify;
              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(identify, mannequin, path, selector, matches);
          }
      }
  }

Hand-coding builders is just a little tedious, however doable, although there are
automated ways to write down them.
Now we will rewrite our Java take a look at circumstances with the Builder, to
obtain better readability:

Java

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

So, the place are we with our assessments? At current, they fail for the flawed motive: null-pointer exceptions
because of the lacking mannequin and path values.
In an effort to get our new take a look at circumstances to fail for the proper motive, 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 will do that
within the take a look at methodology:

Go

  func Test_indexTemplate(t *testing.T) {
    for _, take a look at := vary testCases {
      t.Run(take a look at.identify, func(t *testing.T) {
        if take a look at.mannequin == nil {
          take a look at.mannequin = todo.NewList()
        }
        buf := renderTemplate(take a look at.mannequin, take a look at.path)
        // ... identical as earlier than 
      })
    }
  }

source

In Java, we will present default values within the builder:

Java

  public static remaining class Builder {
      String identify;
      TodoList mannequin = new TodoList();
      String path = "/";
      String selector;
      Checklist<String> matches;
      // ...
  }

source

With these modifications, we see that the final two take a look at circumstances, those for the highlighted hyperlink Energetic
and Accomplished fail, for the anticipated motive 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 assessments cross, 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 assessments 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 assessments now cross.

To recap this part, we made the take a look at code just a little bit extra sophisticated, in order that the take a look at
circumstances are clearer: it is a superb tradeoff!

Loading the web page within the Playwright browser

We begin with a take a look at that can simply load the preliminary HTML. The take a look at
is just a little concerned, so I present the whole 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 sudden requests
        panic("sudden 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("sudden 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, "/");
          
          attempt (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 sudden calls
                      fail(String.format("Sudden request: %s %s", route.request().methodology(), route.request().url()));
                  }
              });
          
              // load preliminary html
              web page.navigate("http://localhost:4567/index.html");
          }
      }
  }

source

At first of the take a look at, 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 is able to begin a headless
browser

Go

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

Java

  attempt (Web page web page = browser.newPage()) {
      logActivity(web page);

The openPage operate 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 operate offers 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.Technique(), 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.methodology(), 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 would possibly 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 sudden requests
      panic("sudden 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 sudden calls
          fail(String.format("Sudden request: %s %s", route.request().methodology(), 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 take a look at; 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 take a look at we are actually in a position to load arbitrary HTML in a
headless browser. Within the subsequent sections we’ll see easy methods 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 strategy to determine particular person todo objects, so
we introduce an Id discipline within the todo merchandise:

Go – up to date mannequin with Id

  kind Merchandise struct {
    Id          int
    Title       string
    IsCompleted bool
  }
  
  func (l *Checklist) AddWithId(id int, title string) *Checklist {
    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 *Checklist) Add(title string) *Checklist {
    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 remaining Checklist<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 report TodoItem(int id, String title, boolean isCompleted) {
      public boolean isActive() {
          return !isCompleted;
      }
  }

And we replace the mannequin in our take a look at so as to add express Ids

Go – including Id within the take a look at 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 take a look at 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 are actually 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 is likely to 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 manner: there’s a
consensus amongst front-end builders that one of the best ways 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 by means of a CSS locator akin to button.purchase; as a substitute,
you search for one thing clickable with the label “Purchase”. In follow,
this implies figuring out components of the web page by means of their
ARIA roles.

To this finish, we add code to our take a look at 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.PageGetByRoleOptions{Title: "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 take a look at, 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 unhealthy accessibility


  <li>
    <div class="view">
      <enter class="toggle" kind="checkbox">
      <label>One</label>
      <button class="destroy"></button>
    </div>
  </li>
We repair it through the use of the for attribute within the

        template,
index.tmpl – Go

  <li>
    <div class="view">
      <enter id="checkbox-{{.Id}}" class="toggle" kind="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" kind="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" kind="checkbox">
      <label for="checkbox-101">One</label>
      <button class="destroy"></button>
    </div>
  </li>
We run once more the take a look at, 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

        easy methods to take a look at that the clicking on a todo merchandise triggers a distant name to the

        server, that ought to end in swapping part of the present HTML with

        the HTML returned by the XHR name.

Spherical-trip to the server

Now we’ll lengthen our take a look at. We inform the take a look at that if name to
POST /toggle/101 is obtained, it ought to return some
stubbed HTML.

Go

  } else if route.Request().URL() == "http://localhost:4567/toggle/101" && route.Request().Technique() == "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().methodology().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/htmx.org@1.9.12" {
    // serve the htmx library
    stubResponse(route, readFile("testdata/htmx.min.js"), "utility/javascript")

Go

  } else if (route.request().url().equals("https://unpkg.com/htmx.org@1.9.12")) {
      // 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 comprises many of the utility is
reloaded.

Go

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

  // verify 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();

  // verify 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 take a look at, 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 identify="viewport" content material="width=device-width, initial-scale=1">
                              <title>Template • TodoMVC</title>
                              <script src="https://unpkg.com/htmx.org@1.9.12"></script>
                            <physique>
                              <part class="todoapp">
                          ...
                                    <li class="">
                                      <div class="view">
                                        <enter id="checkbox-101" class="toggle" kind="checkbox">
                                        <label for="checkbox-101">One</label>
                                        <button class="destroy"></button>
                                      </div>
                                    </li>
                          ...

We are able to make this take a look at cross 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/htmx.org@1.9.12"></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"
      kind="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 ingredient specified by the
part.todoapp CSS locator.

We run once more the take a look at, 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/htmx.org@1.9.12
  << 200 https://unpkg.com/htmx.org@1.9.12
  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 identify="viewport" content material="width=device-width, initial-scale=1">
                              <title>Template • TodoMVC</title>
                              <script src="https://unpkg.com/htmx.org@1.9.12"></script>
                          ...
                            <physique>
                              <part class="todoapp"><part class="todoapp">
                                    <p>Stubbed html</p>
                                  </part></part>
                          ...
                          </physique></html>

The log strains present that the POST name occurred as anticipated, however
examination of the error message reveals that the HTML construction we
anticipated isn’t there: we now have a part.todoapp nested
inside one other. Which means that we aren’t utilizing the HTMX annotations
appropriately, and reveals why this type of take a look at will 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"
      kind="checkbox">

The default behaviour of HTMX is to switch the interior HTML of the
goal ingredient. The data-hx-swap=”outerHTML” annotation
tells HTMX to switch the outer HTML as a substitute.

and we take a look at 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/htmx.org@1.9.12
  << 200 https://unpkg.com/htmx.org@1.9.12
  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/htmx.org@1.9.12
      << 200 https://unpkg.com/htmx.org@1.9.12
      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 easy methods to write a take a look at for the behaviour of our
HTML that, whereas utilizing the sophisticated equipment of a headless browser,
nonetheless feels extra like a unit take a look at than an integration take a look at. It’s in
truth testing simply an HTML web page with any related CSS and JavaScript,
in isolation from different components of the appliance akin to controllers,
providers or repositories.

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

See the ultimate model of the take a look at in Go and in Java.