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Making Screenplay Assertions with Serenity Ensure


Web tests are a common use case for Screenplay scenarios, where we try to model user behaviour and interactions with the system. In this section, we will learn how to interact with a web application using the Screenplay WebDriver integration.

We have seen how make assertions using the should() method with targets or questions combined with Hamcrest matchers, like this:

sam.attemptsTo(  Enter.theValue("40").into(AGE_FIELD).thenHit(Keys.ENTER));
sam.should(    seeThat(the(AGE_FIELD), hasValue("40")));

In the code shown here, the the() method is a static import from the WebElementQuestion class, and the hasValue() is a static import from the WebElementStateMatchers class. This is quite flexible, as you can add custom matchers quite easily. However, it means you need to know what matchers exist, and which ones can be used in different circumstances.

Introducing Serenity Ensure#

Serenity Screenplay also provides an alternative approach, which many developers find easier to use and faster to write. This approach uses the Ensure class. The Ensure class produces a Performable, so you can integrate them directly into the attemptsTo() method. It also has a very readable DSL and lets you use code completion to discover the assertions you can use for different values, making writing assertions easier and quicker. An example of code equivalent to the above can be seen here:

sam.attemptsTo(    Enter.theValue("40").into(AGE_FIELD).thenHit(Keys.ENTER),    Ensure.that(AGE).text().isEqualTo("40"));

In this section, you will learn how to use Serenity Ensure to write fluent assertions for your own projects.

Adding Serenity Ensure to your project#

Serenity Ensure needs an extra dependency in your build script. For Maven, add the serenity-enusre dependency to your pom.xml file:

<dependency>    <groupId>net.serenity-bdd</groupId>    <artifactId>serenity-ensure</artifactId>    <version>${serenity.version}</version>    <scope>test</scope></dependency>

And in Gradle, you need to add the following dependency:

testCompile "net.serenity-bdd:serenity-screenplay-webdriver:${serenity.version}"

Your first Ensure test#

A very simple Ensure test can be seen here:

Actor aster = Actor.named("Aster");
int age = 20;
aster.attemptsTo(    Ensure.that(age).isEqualTo(20)              );

Almost all Ensure assertions start with the Ensure.that() method. This method takes the value being tested as a parameter (in this case an integer). Following this comes the actual assertion method.

Assertions about numbers#

You can use auto-complete in your IDE to see the range of assertions available. For integers, longs and floating point numbers, the assertions include:


For doubles and floats, you can also use the isCloseTo() assertion:

float creditScore = 9.8F;
aster.attemptsTo(    Ensure.that(creditScore).isCloseTo(9.81F, 0.01F));

Assertions about Strings#

Another common requirement is to make assertions about Strings. An example is shown here:

String name = "Bill";aster.attemptsTo(    Ensure.that(name).isEqualToIgnoringCase("BILL"));

Other basic comparison assertions about Strings include the following:


String contents#

The Ensure class also has a number of assertions related to string contents. For example:

String colors = "Red Green Blue";aster.attemptsTo(    Ensure.that(colors).contains("Green"));
containsWhitespaces`Ensure.that("Red Green").containsWhitespaces()
containsOnlyWhitespacesEnsure.that(" ").containsOnlyWhitespaces()
matchesEnsure.that(colors).matches("Red (.*) Blue")
isBlank()Ensure.that(" ").isBlank()

String Size#

There are also some assertions to check the length of the string For example:

String colors = "Red Green Blue";aster.attemptsTo(    Ensure.that(colors).hasSizeGreaterThan(3));

Assertions using Lambda expressions#

Another useful trick is to use a Java 8 Lambda expression to do the check. You can use the Ensure.that(...).matches(...) construct to pass in a lambda predicate which will determine whether the Ensure statement should pass or fail.

For example:

String actualColor = "green";
aster.attemptsTo(    Ensure.that(actualColor).matches("is an RGB color",                                      color -> color.equals("red")                                            || color.equals("blue")                                       || color.equals("green")));

Negative assertions#

You can negate an Ensure.that() statement simply by including the not() method. For example:

String colors = "Red Green Blue";aster.attemptsTo(    Ensure.that(colors).not().contains("Cyan"));

Working with dates and times#

The Ensure class provides a few special methods for dates and times. For LocalTime variables, we can use Ensure.that(...).isBefore() and Ensure.that(...).isAfter() to compare two times, as we can see here:

LocalTime tenInTheMorning = LocalTime.of(10,0);LocalTime twoInTheAfternoon = LocalTime.of(14,0);
aster.attemptsTo(    Ensure.that(tenInTheMorning).isBefore(twoInTheAfternoon));

For LocalDate variables, we have isBefore() and isAfter(), as well as a number of others, such as the isDayOfWeek() method illustrated here:

LocalDate firstOfJanuary = LocalDate.of(2000,1,1);
aster.attemptsTo(    Ensure.that(firstOfJanuary).isDayOfWeek(DayOfWeek.SATURDAY));

Other date-related assertions include:


Working with collections#

The Ensure class gives you a range of methods to make assertions about collections. This can be as simple as checking whether an element appears in a collection: we can do this using the Ensure.that(...).isIn(...) construct:

List<String> colors = Arrays.asList("red", "green", "blue");
aster.attemptsTo(    Ensure.that("red").isIn(colors));

Suppose we had the following lists:

List<String> sameColors = Arrays.asList("red", "green", "blue");List<String> differentColors = Arrays.asList("red", "green", "cyan");List<String> allColors = Arrays.asList("red", "green", "blue","yellow","cyan");List<String> lastColors = Arrays.asList("yellow","cyan");List<String> redAndPink = Arrays.asList("red", "pink");List<String> noColors = Arrays.asList();

Here are some examples of other assertion methods using these collections:

Assertions about list equality and size#

The following assertions are useful if you need to check the size of a collection, or whether it is equivalent to another collection.


Assertions about list contents

Often we need to check the contents of a collection. We can do this using a range of contains assertions, as illustrated here:

List<String> colors = Arrays.asList("red", "green", "blue");
aster.attemptsTo(    Ensure.that(contains).contains("red"));

Some of the other contains assertions are listed in the table below:

startsWithEnsure.that(colors).startsWith("red", "green")

Matching list elements with Java 8 Lambdas#

Lambda expressions provide a powerful way of making arbitrary assertions about the contents of a collection. We can use the Ensure.that(...).allMatch(), Ensure.that(...).anyMatch() and Ensure.that(...).noneMatch() to do this. For example, the following code asserts that each element in a collection is 4 characters long:

List<String> colors = ImmutableList.of("blue", "cyan", "pink");
aster.attemptsTo(    Ensure.that(colors).allMatch("4 characters long",                                 it -> it.length() == 4));

Note that when we use a Lambda expression, we need to include a description of the expectation before providing the lambda expression itself. This description will be used in the reports should the assertion fail.

The anyMatch method checks that there exists at least one element in a collection that matches a specified predicate. An example is shown here:

@Testpublic void shouldContainAtLeastOnePrimaryColor() {    Actor aster = Actor.named("Aster");    List<String> colors = ImmutableList.of("blue", "cyan", "pink");
    aster.attemptsTo(        Ensure.that(colors).anyMatch("is a primary color",                                     it ->  isAPrimaryColor(it))    );}
private boolean isAPrimaryColor(String color) {    return  (color == "red")            || (color == "green")            || (color == "blue");}

The noneMatch method checks that no elements exist in a collection that match a certain condition.

List<String> colors = ImmutableList.of("orange", "cyan", "pink");
aster.attemptsTo(    Ensure.that(colors).noneMatch("is a primary color",                                  it ->  isAPrimaryColor(it)));

You can also check for specific numbers of elements, using atLeast, noMoreThan, and exactly. For example:

List<String> colors = ImmutableList.of("blue", "cyan", "red","pink");
aster.attemptsTo(    Ensure.that(colors).atLeast(2, "is a primary color",                                it ->  isAPrimaryColor(it)));

Using Named Expectations#

If you have commonly used predicates in your test code, you can use the NamedExpectation to make your code more concise. For example, here we define a NamedExpectation that matches primary colors:

private static final  NamedExpectation<String> IS_A_PRIMARY_COLOR        = new NamedExpectation<>("is a primary color",                               color -> (color.equals("red"))                                        || (color.equals("green"))                                        || (color.equals("blue")));

We could use this in the Ensure.that() method like this:

aster.attemptsTo(    Ensure.that(colors).anyMatch(IS_A_PRIMARY_COLOR));

Working with web elements#

When writing UI tests, we need to make assertions about the state of elements on a web page. The Ensure class makes this an easy task.

We can make assertions about Target elements directly using the Ensure.that() method.

Target FIRST_NAME = Target.the("First name field").locatedBy("#firstName")
aster.attemptsTo(    Ensure.that(FIRST_NAME).value().isEqualTo("Joe"),);

A more flexible approach is to use the ElementLocated class to identify an element. We can also locate elements using By locators or CSS/XPath strings. The following code uses the Ensure.that() and methods to check whether the element located by the CSS selector \"#firstName\" is displayed:

aster.attemptsTo(    Ensure.that("#firstName")).isDisplayed(),);

The will work with By locators, XPath/CSS strings or Target elements, which means that you can easily decouple your locator strategy from your assertions.

Simple web element assertions#

The most simple assertions about web elements are boolean checks about the state of the element. The Ensure.that(...).is... assertions let you make assertions about whether an element is displayed or disabled.


Checking text content and field values

Checking field values and text content is the bread-and-butter of many web tests. You can use Ensure.that(...).value() to read the value attribute of a field, as shown here:

aster.attemptsTo(    Ensure.that(FIRST_NAME).value().startsWith("Joe"),);

The Ensure.that(...).text() method lets you read the text of the element:

aster.attemptsTo(    Ensure.that(SEARCH_RESULTS_SUMMARY)          .text()          .endsWith("results for 'Serenity'"),);

You can also read the text contents of an element using Ensure.that(...).textContent(). The text content is the value of the textContent CSS attribute.

This value is available even when an element is not visible, making it useful in cases where you need to read a full set of values, even those not currently visible on the page.

The most important Ensure.that(...) methods for web elements include the following:

attributeEnsure.that(FIRST_NAME).attribute("title").isEqualTo("First name")

All of these methods allow you to make all of the String assertions we saw earlier.

Converting values to different types

Sometimes it is useful to be able to make assertions about non-String types. For example:

aster.attemptsTo(    Ensure.that("#itemCount"))          .value()          .asAnInteger()          .isGreaterThanOrEqualTo(2));

The main conversion methods include:

asABigDecimalEnsure.that(TOTAL_COST).value().asABigDecimal().isEqualTo(new BigDecimal("99.99"))
asABooleanEnsure.that(SOME_FLAG).value().asABoolean().is True()

If a date or time value uses as non-standard format, we can pass a format string to the asADate() or asATime() methods:

aster.attemptsTo(    Ensure.that("#currentDate"))          .value()          .asADate("dd-MM-yyyy")          .isBefore(dateLimit));

Making assertions about collections of web elements

You can make assertions about multiple values, for example, all the titles of a list of search results.

One way to do this is to use the Ensure.thatTheSetOf() method (or its synonym, Ensure.thatAmongst()). This method takes a Target or a locator, and lets you apply the

aster.attemptsTo(        Ensure.thatTheSetOf(".train-line"))              .hasSizeGreaterThan(5));

We can also use static methods defined in TheMatchingElement to perform commonly used checks on web elements, e.g.

aster.attemptsTo(        Ensure.thatTheSetOf(".train-line"))              .allMatch(TheMatchingElement.containsText("Line")));

The main methods defined in the TheMatchingElement class include:

isDisabledEnsure.thatTheSetOf(INPUT_FIELDS).atLeast(1, isDisabled())
isNotDisabledEnsure.thatTheSetOf(INPUT_FIELDS).atLeast(1, isNotDisabled())
isEnabledEnsure.thatTheSetOf(INPUT_FIELDS).atLeast(1, isEnabled())
isNotEnabledEnsure.thatTheSetOf(INPUT_FIELDS).atLeast(1, isNotEnabled())
hasCssClassEnsure.thatTheSetOf(RESULTS).noMoreThan(1, hasCssClass("selected"))
containsOnlyTextEnsure.thatTheSetOf(RESULTS).anyMatch(containsOnlyText("Red Car"))

We can also make assertions about collections of matching values or the text contents of matching elements. We can do this using the Ensure.that(...).values(), Ensure.that(...).textValues() and Ensure.that(...).textContentValues(). For example:

aster.attemptsTo(    Ensure.that("#colors option"))          .values()          .contains("red","blue","green"));

Waiting for elements and defining timeouts#

When working with asynchronous web applications, an element may not be immediately ready when a test interacts with it. By default, Serenity will wait for 5 seconds for an element to be present. Using the Ensure class, we can fine-tune the amount of time we need to wait for an element to become available. For example:

Target SLOW_FIELD = Target.the("Slow field")                          .locatedBy("#slow")
aster.attemptsTo(        Ensure.that(SLOW_FIELD.waitingForNoMoreThan(Duration.ofSeconds(10)))              .value()              .isEqualTo("Marseille"));

We can also build a delay into a Target field, if the same delay should be applied everywhere the element is used:

Target SLOW_FIELD = Target.the("Slow field")                      .locatedBy("#slow")                      .waitingForNoMoreThan(Duration.ofSeconds(5))

Making assertions about the current page#

There are also some Ensure methods that allow us to make basic assertions about the page itself. For example, you can check the page title like this:

aster.attemptsTo(        Ensure.thatTheCurrentPage().title().isEqualTo("Some Title"));

Page-level assertions also include currentUrl(), pageSource() and windowHandle().

Working with Screenplay Questions#

So far we have been using the Ensure.that* methods with web page locators and with field values. We can also use Ensure.that* methods with arbitrary Screenplay questions. This can be used to write custom Question classes or methods that query the state of the application without using the UI, or which do more tailored queries of the UI.

For example,

public Question<Integer> countOf(String todoItem) {    return Question.about("todo status").answeredBy(            actor -> // return some value related to a particular todo item    );}

We could then use the Ensure.thatTheAnswerTo() method to check the result of this question:

aster.attemptsTo(        Ensure.thatTheAnswerTo("the count",                               countOf("some-todo-item"))              .isEqualTo(1));

We can also work with Question classes that return collections, using the Ensure.thatTheAnswersTo() method. Suppose we had a Question that returned a list of Strings:

Question<Collection<String>> colors() {    return Question.about("colors").answeredBy(            actor -> // returns "red","green","blue"    );}

We could then use the Ensure.thatTheAnswersTo() method to make an assertion about this question:

aster.attemptsTo(        Ensure.thatTheAnswersTo(colors()).contains("red"));

Reporting and hiding Ensure steps#

Each Ensure performable will be reported in the Serenity report as a separate step, including a short description of the expectation. Sometimes, however, we want to use the Ensure statement as a way to make sure the application is ready to continue the tests. In these cases, we may prefer to leave the Ensure statement out of the reports.

We can do this using the silently() method:

aster.attemptsTo(    Ensure.that("#firstName"))          .silently()          .isDisplayed());