Take a look at-Driving HTML Templates

Take a look at-Driving HTML Templates
Take a look at-Driving HTML Templates

After a decade or extra the place Single-Web page-Functions generated by
JavaScript frameworks have
become the norm
, we see that server-side rendered HTML is changing into
well-liked once more, additionally because of libraries reminiscent of HTMX or Turbo. Writing a wealthy net UI in a
historically server-side language like Go or Java is not simply attainable,
however a really engaging proposition.

We then face the issue of learn how to write automated assessments for the HTML
elements of our net purposes. Whereas the JavaScript world has developed powerful and sophisticated methods to check the UI,
ranging in measurement from unit-level to integration to end-to-end, in different
languages we wouldn’t have such a richness of instruments obtainable.

When writing an internet software in Go or Java, HTML is usually generated
by templates, which include small fragments of logic. It’s definitely
attainable to check them not directly by end-to-end assessments, however these assessments
are gradual and costly.

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

Degree 1: checking for sound HTML

The primary factor we need to test is that the HTML we produce is
mainly sound. I do not imply to test that HTML is legitimate in response to the
W3C; it could be cool to do it, but it surely’s higher to begin with a lot easier and sooner checks.
For example, we wish our assessments to
break if the template generates one thing like

<div>foo</p>

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

Go

  func Test_wellFormedHtml(t *testing.T) massive

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

Java

  @Take a look at
  void indexIsSoundHtml() b

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

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

Go

  func Test_wellFormedHtml(t *testing.T) abbr

Java

  @Take a look at
  void indexIsSoundHtml() sturdy

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

Go

  func Test_wellFormedHtml(t *testing.T) small

Java

  @Take a look at
  void indexIsSoundHtml() span

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

Go

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

source

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

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

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

Java

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

source

And we see it fail:

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

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

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

Go

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

source

Java

  @Take a look at
  void indexIsSoundHtml() {
      var mannequin = new TodoList();
  
      var html = renderTemplate("/index.tmpl", mannequin);
  
      assertSoundHtml(html);
  }

source

Degree 2: testing HTML construction

What else ought to we check?

We all know that the appears 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 may be usually
logic in templates, and we wish to have the ability to check that logic.

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

What we’d like
is a method to say that some elements of the rendered HTML
correspond to what we count on, and to ignore all the main points we do not
care about.
A technique to do that is by working 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 now have
chosen these components, we (1) depend that the variety of ingredient 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 imagined to generate appears like this:

There are a number of particulars which can be rendered dynamically:

  1. The variety of objects and their textual content content material change, clearly
  2. The model of the todo-item adjustments 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”, “Lively”, “Accomplished” will likely be
    highlighted, relying on the present url; as an example if we resolve that the
    url that exhibits solely the “Lively” objects is /energetic, then when the present url
    is /energetic, 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 considerations might 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 indicate the construction of the checklist objects -->
      <!-- Checklist objects ought to get the category `accomplished` when marked as accomplished -->
      <li class="accomplished">  
        <div class="view">
          <enter class="toggle" kind="checkbox" checked>
          <label>Style JavaScript</label> 
          <button class="destroy"></button>
        </div>
      </li>
      <li>
        <div class="view">
          <enter class="toggle" kind="checkbox">
          <label>Purchase a unicorn</label> 
          <button class="destroy"></button>
        </div>
      </li>
    </ul>
    <footer class="footer">
      <!-- This ought to be `0 objects left` by default -->
      <span class="todo-count"><sturdy>0</sturdy> merchandise left</span> 
      <ul class="filters">
        <li>
          <a class="chosen" href="#/">All</a> 
        </li>
        <li>
          <a href="#/energetic">Lively</a>
        </li>
        <li>
          <a href="#/accomplished">Accomplished</a>
        </li>
      </ul>
      <!-- Hidden if no accomplished objects are left ↓ -->
      <button class="clear-completed">Clear accomplished</button> 
    </footer>
  </part>  

source

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

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

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

Testing HTML content material

The primary check will search for all of the objects, and show that the info
arrange by the check is rendered 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’d like a option to question the HTML doc with our CSS selector; a superb
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 check turns into:

Go

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

source

Java

  @Take a look at
  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 checklist from the
mannequin, this check will fail, as a result of the static template
todo objects have totally different textual content:

Go

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

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

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

Our check works, however it’s a bit verbose, particularly the Go model. If we will have extra
assessments, they’ll grow to be repetitive and tough 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 check right here with t.FatalF
      t.Fatalf("Error rendering template %s", err)
    }
    return doc
  }

Java

  @Take a look at
  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 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 check right here with t.FatalF
      t.Fatalf("Error rendering template %s", err)
    }
    return doc
  }

source

Java

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

source

And with this, we are able to do away with the primary check that we wrote, as we are actually testing for sound HTML on a regular basis.

The second check

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

Go

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

source

Java

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

source

And this check might 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>

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 are able to check and add the varied dynamic options
that our template ought to have.

Make it straightforward so as to add new assessments

The primary of the 20 ideas from the superb talk by Russ Cox on Go
Testing
is “Make it straightforward so as to add new check instances“. Certainly, in Go there
is a bent to make most assessments parameterized, for this very motive.
Then again, whereas Java has
good support
for parameterized tests
with JUnit 5, they are not used as a lot.

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

A check case for us will encompass:

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

So that is the info construction for our check instances:

Go

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

source

Java

  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 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 check:

Go

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

source

Java

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

source

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

Go

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

Java

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

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

Having rewritten our two previous assessments in desk kind, it is now tremendous straightforward so as to add
one other. That is the check for the “x objects left” textual content:

Go

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

source

Java

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

source

And the corresponding change within the html template is:

Go

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

source

Java – jmustache

  <span class="todo-count"><sturdy>{{activeItemsCount}}</sturdy> objects left</span>

source

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

Go

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

source

Java

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

source

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

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

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

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

So we have to cross extra data to the template past the mannequin. A straightforward method
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
    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 check instances desk has yet another area:

Go

  var testCases = []struct {
    title     string
    mannequin    *todo.Checklist
    path     string
    selector string
    matches  []string
  }{
    {
      title: "all todo objects are proven",
      mannequin: todo.NewList().
        Add("Foo").
        Add("Bar"),
      selector: "ul.todo-list li",
      matches:  []string{"Foo", "Bar"},
    },
  // ... the opposite instances
    {
      title:     "highlighted navigation hyperlink: All",
      path:     "/",
      selector: "ul.filters a.chosen",
      matches:  []string{"All"},
    },
    {
      title:     "highlighted navigation hyperlink: Lively",
      path:     "/energetic",
      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 objects are proven",
                      new TodoList()
                              .add("Foo")
                              .add("Bar"),
                      "/",
                      "ul.todo-list li",
                      Checklist.of("Foo", "Bar")),
              // ... the earlier instances
              new TestCase(
                      "highlighted navigation hyperlink: All",
                      new TodoList(),
                      "/",
                      "ul.filters a.chosen",
                      Checklist.of("All")),
              new TestCase(
                      "highlighted navigation hyperlink: Lively",
                      new TodoList(),
                      "/energetic",
                      "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 instances, the mannequin is irrelevant;
whereas for the earlier instances, the trail is irrelevant. The Go syntax permits us
to initialize a struct with simply the fields we’re all in favour of, however Java doesn’t have
the same characteristic, so we’re pushed to cross further data, and this makes the check instances
desk more durable to grasp.

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

We need to optimize for the time of the builders, so it is worthwhile to keep away from including irrelevant
knowledge to our check case. In Java we would cross null for the
irrelevant fields, however there’s a greater method: we are able to use
the builder sample,
popularized by Joshua Bloch.
We are able to rapidly 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 remaining 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 ways to jot down them.
Now we are able to rewrite our Java check instances with the Builder, to
obtain higher readability:

Java

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

So, the place are we with our assessments? At current, they fail for the fallacious motive: null-pointer exceptions
because of the lacking mannequin and path values.
With a view to get our new check instances to fail for the correct motive, particularly that the template does
not but have logic to focus on the proper hyperlink, we should
present default values for mannequin and path. In Go, we are able to do that
within the check technique:

Go

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

source

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

Java

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

source

With these adjustments, we see that the final two check instances, 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 assessments cross, 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 "/energetic" }}chosen{{ finish }}" href="#/energetic">Lively</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="#/energetic">Lively</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
knowledge 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 knowledge = Map.of(
              "mannequin", mannequin,
              "pathRoot", path.equals("/"),
              "pathActive", path.equals("/energetic"),
              "pathCompleted", path.equals("/accomplished")
      );
      return template.execute(knowledge);
  }

source

And with these adjustments, all of our assessments now cross.

To recap this part, we made the check code a bit of bit extra sophisticated, in order that the check
instances are clearer: it is a superb tradeoff!

Degree 3: testing HTML behaviour

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

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

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

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

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

We are going to use the Playwright
library, that’s obtainable for each Go and
Java. The assessments we
are going to jot down will likely be slower, as a result of we must wait a couple of
seconds for the headless browser to begin, however will retain among the
essential traits of unit assessments, primarily that we’re testing
simply the HTML (and any related CSS and JavaScript), in isolation from
every other server-side logic.

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

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

Loading the web page within the Playwright browser

We begin with a check that may simply load the preliminary HTML. The check
is a bit of 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();
      }
  
      @Take a look at
      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().technique(), route.request().url()));
                  }
              });
          
              // load preliminary html
              web page.navigate("http://localhost:4567/index.html");
          }
      }
  }

source

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

Go

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

Java

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

Then we open the Playwright “web page”, which 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 gives suggestions on what
the web page is doing

Go

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

Java

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

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

Go

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

and we ask the web page to load the preliminary HTML

Go

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

Java

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

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

Go

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

Java

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

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

Figuring out todo objects

Now we need to click on on the “One” checkbox. The issue we now have is
that at current, we now have no option to establish particular person todo objects, so
we introduce an Id area 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 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 document TodoItem(int id, String title, boolean isCompleted) {
      public boolean isActive() {
          return !isCompleted;
      }
  }

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

Go – including Id within the check 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 check knowledge

  @Take a look at
  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 need to simulate person interplay with the HTML web page. It is perhaps
tempting to proceed to make use of CSS selectors to establish the precise
checkbox that we need 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 use it
the same way that users do
. For example, you do not search for a
button by a CSS locator reminiscent of button.purchase; as a substitute,
you search for one thing clickable with the label “Purchase”. In follow,
this implies figuring out elements of the web page by their
ARIA
roles.

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

Go

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

Java

  @Take a look at
  void toggleTodoItem() {
          // ...
          // click on on the "One" checkbox
          var checkbox = web page.getByRole(AriaRole.CHECKBOX, new Web page.GetByRoleOptions().setName("One"));
          checkbox.click on();
      }
  }

We run the check, and it fails:

Go

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

Java

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

generated HTML with unhealthy accessibility

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

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

index.tmpl – Go

  <li>
    <div class="view">
      <enter id="checkbox-{{.Id}}" class="toggle" 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 check, and it passes.

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

Spherical-trip to the server

Now we’ll lengthen our check. We inform the check 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().Methodology() == "POST" {
    // we count on {that a} POST /toggle/101 request is made after we click on on the "One" checkbox
    const stubbedHtml = `
      <part class="todoapp">
        <p>Stubbed html</p>
      </part>`
    stubResponse(route, stubbedHtml, "textual content/html")

Java

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

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

Go

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

Go

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

Lastly, we add the expectation that, after we click on the checkbox,
the part of the HTML that comprises 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 check, 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 may 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 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  : ""
                          ...
            Take a look at:         Test_toggleTodoItem
            Messages:     <!DOCTYPE html><html lang="en"><head>
                              <meta charset="utf-8">
                              <meta title="viewport" content material="width=device-width, initial-scale=1">
                              <title>Template • TodoMVC</title>
                              <script src="https://unpkg.com/[email protected]"></script>
                            <physique>
                              <part class="todoapp">
                          ...
                                    <li class="">
                                      <div class="view">
                                        <enter id="checkbox-101" class="toggle" kind="checkbox">
                                        <label for="checkbox-101">One</label>
                                        <button class="destroy"></button>
                                      </div>
                                    </li>
                          ...

We are able to make this check 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/[email protected]"></script>

Then we add the HTMX attributes to the checkboxes:

index.tmpl

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

The data-hx-post annotation will make HTMX do a POST
name to the required 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 check, and it nonetheless fails!

Go – Java is comparable

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

The log strains present that the POST name occurred as anticipated, however
examination of the error message exhibits that the HTML construction we
anticipated just isn’t there: we now have a part.todoapp nested
inside one other. Because of this we aren’t utilizing the HTMX annotations
appropriately, and exhibits why this sort of check might be beneficial. 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 interchange the inside HTML of the
goal ingredient. The data-hx-swap="outerHTML" annotation
tells HTMX to interchange the outer HTML as a substitute.

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

Go

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

Java

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

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

The check prices 2-3 seconds of ready time for the headless browser to come back up, which is often an excessive amount of for a unit check; nevertheless, like a unit check, 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 check in Go and in Java.

Bonus degree: Stringly asserted

Esko Luontola, TDD knowledgeable and writer of the web course tdd.mooc.fi, suggested an alternative to testing HTML with CSS selectors: the concept is to rework HTML right into a human-readable canonical kind.

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

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

We may visualize the above HTML by:

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

to reach at:

One Two Three

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

<enter worth="foo" />

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

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

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

Go — Java is comparable

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

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

Go

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

Java

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

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

Go

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

source

Java

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

source

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

This system of asserting towards giant, sophisticated knowledge constructions reminiscent of HTML pages by decreasing them to a canonical string model has no title that I do know of. Martin Fowler suggested “stringly asserted”, and from his suggestion comes the title of this part.