I'm tasked by Dr. Emmett Brown to help Marty McFly travel to different time periods successfully on Doc's time machine -
DeLorean!However, I must ensure DeLorean must at least hit the speed of 88 miles per hour (142 km/h) for the
flux capacitor to kick-in, then a big ZAP and vanishes from sight.
Below is the source code:
package delorean;
import java.util.Date;
public class DeLorean {
private static final int MAX_SPEED_MPH = 88;
public boolean timeTravel(Date date, int speedMPH) {
System.out.println("Setting DeLorean target date " + date);
if (prepareTimeTravel(speedMPH)) {
System.out.println("Time travel was successful, we are now on " + date);
return true;
}
System.out.println("Time travel failed");
return false;
}
private boolean prepareTimeTravel(int speedMPH) {
// we need at least 88 mph or equivalent to 142 km/h
// to activate flux capacitor for time travel
if (speedMPH >= MAX_SPEED_MPH) {
System.out.println("Activating flux capacitor");
return true;
}
return false;
}
}
I also wrote a unit-test to ensure the flux capacitor activates once speed is at 88 mph during Marty's travel:
package delorean;
import java.util.Calendar;
import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;
public class DeLoreanTest {
private static Calendar future;
private DeLorean deLorean;
static {
future = Calendar.getInstance();
future.set(Calendar.YEAR, 2015);
future.set(Calendar.DAY_OF_MONTH, 21);
future.set(Calendar.MONTH, Calendar.OCTOBER);
}
@Before
public void init() {
deLorean = new DeLorean();
}
@Test
public void testTimeTravelSuccess() {
Assert.assertTrue(deLorean.timeTravel(future.getTime(), 88));
}
@Test
public void testTimeTravelFailed() {
Assert.assertFalse(deLorean.timeTravel(future.getTime(), 87));
}
}
Below is the result of the test:
Setting DeLorean target date Wed Oct 21 03:03:50 EST 2015
Activating flux capacitor
Time travel was successful, we are now on Wed Oct 21 03:03:50 EST 2015
Setting DeLorean target date Wed Oct 21 03:03:50 EST 2015
Time travel failed
Everything looks fine, but...OK I admit I'm test infected and I really feel the urge to also test "prepareTimeTravel" method alone by itself. However, how am I suppose to do this when it's defined as a private method? Surely I can turn this to public but I'd rather keep this abstracted away from Marty as he doesn't need to know the nitty-gritty details between the car's acceleration and the flux capacitor. All he needs to know is to step on accelerator pedal to reach 88 miles per hour and *poof* he goes.
*Thinking, thinking, thinking...*What about setting this method as package scope? This means "prepareTimeTravel" method will only be visible to classes of the same package, including DeLoreanTest class (same package name)^. This also ensure classes from other packages won't see this method. This sounds like what I'm looking for.
package delorean;
import java.util.Date;
public class DeLorean {
private static final int MAX_SPEED_MPH = 88;
public boolean timeTravel(Date date, int speedMPH) {
System.out.println("Setting DeLorean target date " + date);
if (prepareTimeTravel(speedMPH)) {
System.out.println("Time travel was successful, we are now on " + date);
return true;
}
System.out.println("Time travel failed");
return false;
}
boolean prepareTimeTravel(int speedMPH) {
// we need at least 88 mph or equivalent to 142 km/h
// to activate flux capacitor for time travel
if (speedMPH >= MAX_SPEED_MPH) {
System.out.println("Activating flux capacitor");
return true;
}
return false;
}
}
The updated unit-test looks like this:
package delorean;
import java.util.Calendar;
import junit.framework.Assert;
import org.junit.Before;
import org.junit.Test;
public class DeLoreanTest {
private static Calendar future;
private DeLorean deLorean;
static {
future = Calendar.getInstance();
future.set(Calendar.YEAR, 2015);
future.set(Calendar.DAY_OF_MONTH, 21);
future.set(Calendar.MONTH, Calendar.OCTOBER);
}
@Before
public void init() {
deLorean = new DeLorean();
}
@Test
public void testTimeTravelSuccess() {
Assert.assertTrue(deLorean.timeTravel(future.getTime(), 88));
}
@Test
public void testTimeTravelFailed() {
Assert.assertFalse(deLorean.timeTravel(future.getTime(), 87));
}
@Test
public void testPrepareTimeTravelSuccess() {
Assert.assertTrue(deLorean.prepareTimeTravel(88));
Assert.assertTrue(deLorean.prepareTimeTravel(89));
Assert.assertTrue(deLorean.prepareTimeTravel(90));
}
@Test
public void testPrepareTimeTravelFailed() {
Assert.assertFalse(deLorean.prepareTimeTravel(87));
Assert.assertFalse(deLorean.prepareTimeTravel(86));
}
}
Vroooom... ZAP - *poof*
^ When using Maven, DeLorean class sits under "src/main/java directory" and DeLoreanTest class sits under "src/test/java" directory. Both classes contains same package name, hence package-scope method "prepareTimeTravel" will be visible to test class.
