Java Reference
In-Depth Information
should reduce dependencies as much as possible. If your classes depend on many
other classes that need to be instantiated and set up with some state, then your tests
will be complicated—you may need to use some complicated mock-objects solution
(see chapter 6 for mock objects).
A solution to reducing dependencies is to separate your code between methods
that instantiate
new
objects (factories) and methods that provide your application
logic. Consider listing 5.1.
Listing 5.1
Reduce dependencies
class
Vehicle {
Driver d =
new
Driver();
boolean
hasDriver = true;
private
void
setHasDriver(
boolean
hasDriver) {
this.hasDriver = hasDriver;
}
}
Every time we instantiate the
Vehicle
object, we also instantiate the
Driver
object.
We've mixed the concepts. The solution would be to have the
Driver
interface
passed
to the
Vehicle
class, as in listing 5.2.
Listing 5.2
Pass the
Driver
to the
Vehicle
class
Vehicle {
Driver d;
boolean
hasDriver =
true
;
Vehicle(Driver d) {
this
.d = d;
}
private
void
setHasDriver(
boolean
hasDriver) {
this.hasDriver = hasDriver;
}
}
This allows us to produce a
mock
Driver
object (see chapter 6) and pass it to the
Vehicle
class on instantiation. Furthermore, we can
mock
any other type of
Driver
implemen-
tation—
JuniorDriver
,
SeniorDriver
, and so on—and pass it to the
Vehicle
class.
5.2.3
Create simple constructors
By striving for better test coverage, we add more and more test cases. In each of these
test cases, we do the following:
Instantiate the class to test
■
Set the class into a particular state
■
Assert the final state of the class
■
