com.hp.util.test

Class FakeTimeUtils

java.lang.Object

com.hp.util.test.FakeTimeUtils

public final class FakeTimeUtils
extends Object

Implements a fake TimeUtils, suitable for unit tests to carefully control the time returned by TimeUtils.currentTimeMillis().

The fake TimeUtils starts its clock at midnight January 1st, 2013, and thereafter every call to currentTimeMillis() either:

• automatically advances the time by 10 milliseconds, or
• does not advance the time

In the latter case, it is up to the consumer to invoke advanceMs(long) to change the time.

A production "event" class may look something like this (javadocs omitted for conciseness):

 public class FooEvent {
     static TimeUtils TIME = TimeUtils.getInstance();
     ...

     private final long ts = TIME.currentTimeMillis();

     public FooEvent(...) {
         ...
     }

     public long ts() {
         return ts;
     }

     @Override
     public String toString() {
         return "{" + TIME.hhmmssnnn(ts) + ... + "}";
     }
 }
 

Notice how the TimeUtils instance is stored in a static, package-private field. Under production conditions, the ts instance field is set to system time during construction.

A unit test for the class might look something like this, using the default behavior of FakeTimeUtils whereby the clock is advanced 10ms after every call to currentTimeMillis():

 public class FooEventTest {
     private FakeTimeUtils fake;

     @Before
     public void setUp() {
         fake = FakeTimeUtils.getInstance();
         FooEvent.TIME = fake.timeUtils();
     }

     @Test
     public void basic() {
         long startTs = fake.getCurrent();
         FooEvent e1 = new FooEvent();
         FooEvent e2 = new FooEvent();
         FooEvent e3 = new FooEvent();
         assertEquals(AM_NEQ, startTs, e1.ts());
         assertEquals(AM_NEQ, startTs + 10, e2.ts());
         assertEquals(AM_NEQ, startTs + 20, e3.ts());
     }
 }
 

Alternatively, a unit test might wish to exert exact control over the time values returned:

 public class FooEventTest {
     private static final long FIVE_K = 5000;

     private FakeTimeUtils fake;

     @Before
     public void setUp() {
         fake = FakeTimeUtils.getInstance(Advance.MANUAL);
         FooEvent.TIME = fake.timeUtils();
     }

     @Test
     public void basic() {
         long startTs = fake.getCurrent();
         FooEvent e1 = new FooEvent();
         FooEvent e2 = new FooEvent();
         FooEvent e3 = new FooEvent();
         assertEquals(AM_NEQ, startTs, e1.ts());
         assertEquals(AM_NEQ, startTs, e2.ts());
         assertEquals(AM_NEQ, startTs, e3.ts());

         fake.advanceMs(FIVE_K);
         FooEvent e4 = new FooEvent();
         assertEquals(AM_NEQ, startTs + FIVE_K, e4.ts());
     }
 }
 

Author:

Simon Hunt

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	FakeTimeUtils.Advance Denotes how time will advance when TimeUtils.currentTimeMillis() is invoked.

Field Summary

Fields

Modifier and Type	Field and Description
static int	TICK_SIZE Increment clock by 10ms per call.

Method Summary

Methods

Modifier and Type	Method and Description
void	advanceMs(long ms) Advances the clock by the specified number of milliseconds.
long	getCurrent() Returns the current value of the clock, i.e. the value that will be returned from the next invocation of currentTimeMillis() on the TimeUtils instance.
static FakeTimeUtils	getInstance() Returns a fake TimeUtils instance with the behavior of advancing the clock by 10ms after every call to TimeUtils.currentTimeMillis().
static FakeTimeUtils	getInstance(FakeTimeUtils.Advance advance) Returns a fake TimeUtils instance with the specified behavior.
TimeUtils	timeUtils() Returns the patched time-utils instance to attach to the class under test.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

TICK_SIZE

public static final int TICK_SIZE

Increment clock by 10ms per call.

See Also:

Constant Field Values

Method Detail

timeUtils

public TimeUtils timeUtils()

Returns the patched time-utils instance to attach to the class under test.

Returns:

the patched time-utils

advanceMs

public void advanceMs(long ms)

Advances the clock by the specified number of milliseconds.

Parameters:

ms - the number of milliseconds to advance

getCurrent

public long getCurrent()

Returns the current value of the clock, i.e. the value that will be returned from the next invocation of currentTimeMillis() on the TimeUtils instance.

Returns:

the current value of the clock

getInstance

public static FakeTimeUtils getInstance()

Returns a fake TimeUtils instance with the behavior of advancing the clock by 10ms after every call to TimeUtils.currentTimeMillis().

Returns:

the fake TimeUtils

getInstance

public static FakeTimeUtils getInstance(FakeTimeUtils.Advance advance)

Returns a fake TimeUtils instance with the specified behavior.

Parameters:

advance - the required clock advancement behavior

Returns:

fake TimeUtils