Check-Driving HTML Templates

What else ought to we take a look at?

We all know that the appears to be like 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. Nonetheless, there’s usually
logic in templates, and we wish 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 include a number of
particulars that make string equality assertions impractical. The assertions
turn out to be very verbose, and when studying the assertion, it turns into troublesome
to grasp what it’s that we’re making an attempt to show.

What we want
is a way to claim that some components of the rendered HTML
correspond to what we count on, 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 out the
components that we care about from the entire HTML doc. As soon as we have now
chosen these components, we (1) rely that the variety of aspect returned
is what we count on, and (2) that they include the textual content or different content material
that we count on.

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

There are a number of particulars which are rendered dynamically:

1. The variety of gadgets and their textual content content material change, clearly
2. The type of the todo-item adjustments when it is accomplished (e.g., the
   second)
3. The “2 gadgets left” textual content will change with the variety of non-completed
   gadgets
4. One of many three buttons “All”, “Lively”, “Accomplished” shall be
   highlighted, relying on the present url; as an example if we determine that the
   url that reveals solely the “Lively” gadgets is /lively, then when the present url
   is /lively, the “Lively” button ought to 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 may 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, supplied for instance:

index.tmpl

  <part class="todoapp">
    <ul class="todo-list">
      <!-- These are right here simply to point out the construction of the listing gadgets -->
      <!-- Checklist gadgets 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 gadgets 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">Lively</a>
        </li>
        <li>
          <a href="#/accomplished">Accomplished</a>
        </li>
      </ul>
      <!-- Hidden if no accomplished gadgets are left ↓ -->
      <button class="clear-completed">Clear accomplished</button> ⑤
    </footer>
  </part>  

supply

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

We are able to use these selectors to focus our exams 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 gadgets, and show that the info
arrange by the take a look at 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’d like a solution 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 hold 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 {
    // A bit mess as a consequence of 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())
  }

supply

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");
  }

supply

If we nonetheless have not modified the template to populate the listing from the
mannequin, this take a look at will fail, as a result of the static template
todo gadgets have totally different textual content:

Go

  --- FAIL: Test_todoItemsAreShown (0.00s)
      index_template_test.go:44: First listing merchandise: need Foo, acquired Style JavaScript
      index_template_test.go:49: Second listing merchandise: need Bar, acquired 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 knowledge:

Go

  <ul class="todo-list">
    {{ vary .Objects }}
      <li>
        <div class="view">
          <enter class="toggle" kind="checkbox">
          <label>{{ .Title }}</label>
          <button class="destroy"></button>
        </div>
      </li>
    {{ finish }}
  </ul>

supply

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>

supply

Check each content material and soundness on the similar time

Our take a look at works, however it’s a bit verbose, particularly the Go model. If we will have extra
exams, they may turn out to be repetitive and troublesome 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 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, "");
  }

Significantly better! At the least for my part. Now that we extracted the parseHtml helper, it is
a good suggestion to test 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
  }

supply

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;
  }

supply

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 listing is “Checklist gadgets 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]))
  }

supply

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");
  }

supply

And this take a look at may be made inexperienced by including this little bit of logic to the
template:

Go

  <ul class="todo-list">
    {{ vary .Objects }}
      <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>

supply

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>

supply

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

Make it straightforward so as to add new exams

The primary of the 20 ideas from the wonderful speak by Russ Cox on Go
Testing is “Make it straightforward so as to add new take a look at circumstances“. Certainly, in Go there
is an inclination to make most exams parameterized, for this very motive.
Alternatively, whereas Java has
good assist
for parameterized exams with JUnit 5, they are not used as a lot.

Since our present two exams 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 look forward to finding once 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 {
    title     string
    mannequin    *todo.Checklist
    selector string
    matches  []string
  }{
    {
      title: "all todo gadgets are proven",
      mannequin: todo.NewList().
        Add("Foo").
        Add("Bar"),
      selector: "ul.todo-list li",
      matches:  []string{"Foo", "Bar"},
    },
    {
      title: "accomplished gadgets get the 'accomplished' class",
      mannequin: todo.NewList().
        Add("Foo").
        AddCompleted("Bar"),
      selector: "ul.todo-list li.accomplished",
      matches:  []string{"Bar"},
    },
  }

supply

Java

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

supply

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.title, 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), "surprising # of matches")
        for i, node := vary choice.Nodes {
          assert.Equal(t, take a look at.matches[i], textual content(node))
        }
      })
    }
  }

supply

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.measurement());
      for (int i = 0; i < take a look at.matches.measurement(); i++) {
          assertThat(choice.get(i).textual content()).isEqualTo(take a look at.matches.get(i));
      }
  }

supply

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

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
  
  > Activity :take a look at
  
  IndexTemplateTest > testIndexTemplate(TestCase) > [1] all todo gadgets are proven PASSED
  IndexTemplateTest > testIndexTemplate(TestCase) > [2] accomplished gadgets get the 'accomplished' class PASSED

Observe 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 previous exams in desk type, it is now tremendous straightforward so as to add
one other. That is the take a look at for the “x gadgets left” textual content:

Go

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

supply

Java

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

supply

And the corresponding change within the html template is:

Go

  <span class="todo-count"><robust>{{len .ActiveItems}}</robust> gadgets left</span>

supply

Java – jmustache

  <span class="todo-count"><robust>{{activeItemsCount}}</robust> gadgets left</span>

supply

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

Go

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

supply

Java

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

supply

We have invested a bit of 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 subsequent 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”, “Lively” and “Accomplished” navigation hyperlinks at
the underside of the UI (see the image above),
and these depend upon which url we’re visiting, which is
one thing that our template has no solution to discover out.

At present, all we move to our template is our mannequin, which is a todo-list.
It isn’t right so as to add the at present visited url to the mannequin, as a result of that’s
consumer navigation state, not software 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.Checklist, path string) bytes.Buffer {
    templ := template.Should(template.ParseFiles("index.tmpl"))
    var buf bytes.Buffer
    knowledge := map[string]any{
      "mannequin": mannequin,
      "path":  path,
    }
    err := templ.Execute(&buf, knowledge)
    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 knowledge = Map.of(
              "mannequin", mannequin,
              "path", path
      );
      return template.execute(knowledge);
  }

And correspondingly our take a look at circumstances desk has yet another discipline:

Go

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

Java

  document TestCase(String title,
                  TodoList mannequin,
                  String path,
                  String selector,
                  Checklist<String> matches) {
      @Override
      public String toString() {
          return title;
      }
  }
  
  public static TestCase[] indexTestCases() {
      return new TestCase[]{
              new TestCase(
                      "all todo gadgets 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: Lively",
                      new TodoList(),
                      "/lively",
                      "ul.filters a.chosen",
                      Checklist.of("Lively")),
              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 focused on, however Java doesn’t have
an analogous function, so we’re pushed to move additional info, and this makes the take a look at circumstances
desk tougher to grasp.

A developer may take 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 unique path. In the identical method, when studying the
highlighted navigation hyperlink take a look at circumstances, the developer may surprise if the
anticipated conduct is determined by the mannequin being set to an empty todo listing. If that’s the case, one may
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
knowledge to our take a look at case. In Java we would move null for the
irrelevant fields, however there’s a greater method: we will use
the builder sample,
popularized by Joshua Bloch.
We are able to shortly write one for the Java TestCase document this fashion:

Java

  document TestCase(String title,
                  TodoList mannequin,
                  String path,
                  String selector,
                  Checklist<String> matches) {
      @Override
      public String toString() {
          return title;
      }
  
      public static closing class Builder {
          String title;
          TodoList mannequin;
          String path;
          String selector;
          Checklist<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 methods 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()
                      .title("all todo gadgets are proven")
                      .mannequin(new TodoList()
                              .add("Foo")
                              .add("Bar"))
                      .selector("ul.todo-list li")
                      .matches("Foo", "Bar")
                      .construct(),
              // ... different circumstances
              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 incorrect motive: null-pointer exceptions
because of the lacking mannequin and path values.
With a view to get our new take a look at circumstances to fail for the fitting motive, particularly that the template does
not but have logic to spotlight 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.title, 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)
        // ... similar as earlier than 
      })
    }
  }

supply

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

Java

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

supply

With these adjustments, we see that the final two take a look at circumstances, those for the highlighted hyperlink Lively
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: "Lively"
                          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: Lively FAILED
      org.opentest4j.AssertionFailedError:
      Anticipating:
       <"All">
      to be equal to:
       <"Lively">
      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 adjustments 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">Lively</a>
    </li>
    <li>
      <a class="{{ if eq .path "/accomplished" }}chosen{{ finish }}" href="#/accomplished">Accomplished</a>
    </li>
  </ul>

supply

Java – jmustache

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

supply

Because the Mustache template language doesn’t permit for equality testing, we should change the
knowledge 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 knowledge = Map.of(
              "mannequin", mannequin,
              "pathRoot", path.equals("/"),
              "pathActive", path.equals("/lively"),
              "pathCompleted", path.equals("/accomplished")
      );
      return template.execute(knowledge);
  }

supply

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

To recap this part, we made the take a look at code a bit of bit extra difficult, in order that the take a look at
circumstances are clearer: it is a excellent 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 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())
    }
  }

supply

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("Surprising request: %s %s", route.request().methodology(), route.request().url()));
                  }
              });
          
              // load preliminary html
              web page.navigate("http://localhost:4567/index.html");
          }
      }
  }

supply

Firstly of the take a look at, we initialize the mannequin with two todo
gadgets “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 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 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("Surprising 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 capable of load arbitrary HTML in a
headless browser. Within the subsequent sections we’ll see the best way to simulate consumer
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 gadgets

Now we wish to click on on the “One” checkbox. The issue we have now is
that at current, we have now no solution to establish particular person todo gadgets, 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.Objects = append(l.Objects, &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.Objects = append(l.Objects, &merchandise)
    return l
  }
  
  func generateRandomId() int {
    return abs(rand.Int())
  }

Java – up to date mannequin with Id

  public class TodoList {
      non-public closing Checklist<TodoItem> gadgets = new ArrayList<>();
  
      public TodoList add(String title) {
          gadgets.add(new TodoItem(generateRandomId(), title, false));
          return this;
      }
  
      public TodoList addCompleted(String title) {
          gadgets.add(new TodoItem(generateRandomId(), title, true));
          return this;
      }
  
      public TodoList add(int id, String title) {
          gadgets.add(new TodoItem(id, title, false));
          return this;
      }
  
      non-public static int generateRandomId() {
          return new Random().nextInt(0, Integer.MAX_VALUE);
      }
  }
  
  public document 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 specific Ids

Go – including Id within the take a look at knowledge

  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 knowledge

  @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 consumer interplay with the web page.

Clicking on a todo merchandise

We wish to simulate consumer interplay with the HTML web page. It is likely to be
tempting to proceed to make use of CSS selectors to establish the particular
checkbox that we wish to click on, however there’s a greater method: there’s a
consensus amongst front-end builders that one of the simplest ways to check
interplay with a web page is to make use of it
the identical method that customers do. For example, you do not search for a
button by way 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 way 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 enhancing

        accessibility of our generated HTML. Within the subsequent part, we'll see

        the best way to take a look at that the press 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 take a look at. We inform the take a look at 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().Technique() == "POST" {
    // we count on {that a} POST /toggle/101 request is made once 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 count on {that a} POST /toggle/101 request is made once 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"), "software/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 incorporates many of the software 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)
  }

  // test 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();

  // test 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. With a view 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 could be very verbose, however we see that the rationale 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 analogous

  --- 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/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 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/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 aspect specified by the
part.todoapp CSS locator.

We run once more the take a look at, and it nonetheless fails!

Go – Java is analogous

  --- 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 title="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 traces present that the POST name occurred as anticipated, however
examination of the error message reveals that the HTML construction we
anticipated just isn’t there: we have now a part.todoapp nested
inside one other. Because of this we’re not utilizing the HTMX annotations
accurately, and reveals why this sort of take a look at may be worthwhile. 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 exchange the interior HTML of the
goal aspect. The data-hx-swap="outerHTML" annotation
tells HTMX to exchange 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 the best way to write a take a look at for the behaviour of our
HTML that, whereas utilizing the difficult 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
reality testing simply an HTML web page with any related CSS and JavaScript,
in isolation from different components of the appliance akin to controllers,
companies or repositories.

The take a look at prices 2-3 seconds of ready time for the headless browser to return up, which is often an excessive amount of for a unit take a look at; nevertheless, like a unit take a look at, it is rather 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.