Design and Architectural Principles - Java 8 Lambdas - page 134

public public static void describe ( String name , Suite behavior ) {

Description description = new

static void

new Description ( name );
behavior . specifySuite ( description );

}

Each suite has its code description implemented by the user using a lambda expression. This
means that we need a Suite functional interface, shown in Example 8-30 , to represent a suite
of specifications. You'll notice it also takes a Description object as an argument, which we
passed into it from the describe method.

Example 8-30. Each suite of tests is a lambda expression implementing this interface
public

public interface interface Suite Suite {

public public void void specifySuite ( Description description );

}

Not only are suites represented by lambda expressions in our DSL, but so are individual spe-
cifications. They also need a functional interface, which I'll call Specification
( Example 8-31 ) . The variable called expect in our code sample is an instance of our Expect
class, which I'll describe later.

Example 8-31. Each specification is a lambda expression implementing this interface
public public interface interface Specification Specification {

public public void void specifyBehaviour ( Expect expect );

}

The Description instance we've been passing around comes in handy at this point. We
want our users to be able to fluently name their specifications with the it.should clause.
This means our Description class needs a should method (see Example 8-32 ) . This is
where the real work gets done, as this is the method that actually executes the lambda expres-
sion by calling its specifySuite method. Specifications will tell us they have failed by
throwing the standard Java AssertionError , and we consider any other Throwable to be an
error.

Example 8-32. Our specification lambda expressions get passed into the should method
public

public void void should ( String description , Specification specification ) {

try try {

Expect expect = new new Expect ();