I have a very simple file watcher class which checks every 2 seconds if a file has changed and if so, the onChange
method (void) is called.
Is there an easy way to check if the onChange
method is getting called in a unit test?
code:
public class PropertyFileWatcher extends TimerTask {
private long timeStamp;
private File file;
public PropertyFileWatcher(File file) {
this.file = file;
this.timeStamp = file.lastModified();
}
public final void run() {
long timeStamp = file.lastModified();
if (this.timeStamp != timeStamp) {
this.timeStamp = timeStamp;
onChange(file);
}
}
protected void onChange(File file) {
System.out.println("Property file has changed");
}
}
Test:
@Test
public void testPropertyFileWatcher() throws Exception {
File file = new File("testfile");
file.createNewFile();
PropertyFileWatcher propertyFileWatcher = new PropertyFileWatcher(file);
Timer timer = new Timer();
timer.schedule(propertyFileWatcher, 2000);
FileWriter fw = new FileWriter(file);
fw.write("blah");
fw.close();
Thread.sleep(8000);
// check if propertyFileWatcher.onChange was called
file.delete();
}
With Mockito, you can verify whether a method is called at least once/never.
See point 4 in this page
eg:
verify(mockedObject, times(1)).onChange(); // times(1) is the default and can be omitted
Here is a simple modification for your test.
@Test
public void testPropertyFileWatcher() throws Exception {
final File file = new File("testfile");
file.createNewFile();
final AtomicBoolean hasCalled = new AtomicBoolean( );
PropertyFileWatcher propertyFileWatcher =
new PropertyFileWatcher(file)
{
protected void onChange ( final File localFile )
{
hasCalled.set( true );
assertEquals( file, localFile );
}
}
Timer timer = new Timer();
timer.schedule(propertyFileWatcher, 2000);
FileWriter fw = new FileWriter(file);
fw.write("blah");
fw.close();
Thread.sleep(8000);
// check if propertyFileWatcher.onChange was called
assertTrue( hasCalled.get() );
file.delete();
}
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