Can you mock a database?

Hello!
I'm currently working on a webapp which interracts with a db, quite alot actually.
As it is right now, all my tests make calls to the existing db.
I've heard about test databases which contain test data, how do I create one, and how do I use it in my test cases?

Also, my update and remove use the primary key(an auto-incrementing int called id) to identify which row to update/remove. (Kind of obvious eh..)
Anyway, this means that in my test case I need to send in an int with the remove/update methods,
but since the id is AI the int I send in has to change each time I run the test case.
How can I change that? It's rather tedious to always make sure that there is a row with the id I make the call with.
Will "mocking" the database help with this issue?

Appreciate any help,
Alia

Alia,
While you could mock a database, it sounds like you want to use a real database - just a different one. I suggest taking a look at dbUnit. it allows you to always test with the database in the same state. Which eliminates the row being present problem you described.

dbUnit, right! I'll check it out, thank you!

Right so I've downloaded the DBUnit .jar and it's in put snuggly along with the other .jars (JUnit, mysql-connector etc.)
But I'm having a problem with using it. I found a tutorial, which I more or less copied and then made to fit my own tests,
this is it:

import java.sql.Connection;
import java.sql.DriverManager;

import org.dbunit.DatabaseTestCase;
import org.dbunit.database.DatabaseConnection;
import org.dbunit.database.IDatabaseConnection;
import org.dbunit.dataset.IDataSet;
import org.dbunit.dataset.xml.FlatXmlDataSet;

public class TestDbUnit extends DatabaseTestCase{
	public static final String TABLE_RESERVATION = "reservation";
	private FlatXmlDataSet loadedDataSet;

// Provide a connection to the database
	protected IDatabaseConnection getConnection() throws Exception{
		Class driverClass = Class.forName("com.mysql.jdbc.Driver");
		Connection jdbcConnection = 
		      DriverManager.getConnection("jdbc:mysql://localhost/konfbooking", "root", "");
		return new DatabaseConnection(jdbcConnection);
	}
	// Load the data which will be inserted for the test
	protected IDataSet getDataSet() throws Exception{
		loadedDataSet = new 							
			FlatXmlDataSet(this.getClass().getClassLoader().getResourceAsStream("input.xml"));
		return loadedDataSet;
	}
	// Check that the data has been loaded.
	public void testCheckLoginDataLoaded() throws Exception{
		assertNotNull(loadedDataSet);
		int rowCount = loadedDataSet.getTable(TABLE_RESERVATION).getRowCount();
		assertEquals(2, rowCount);
	}
}

Is there anything visibly wrong with it?

When I run the test I get this error message:

java.lang.NoClassDefFoundError: org/apache/commons/logging/LogFactory
at org.slf4j.impl.JCLLoggerFactory.getLogger(JCLLoggerFactory.java:69)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:209)
at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:221)
at org.dbunit.DatabaseTestCase.<clinit>(DatabaseTestCase.java:50)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
at java.lang.reflect.Constructor.newInstance(Unknown Source)
at junit.framework.TestSuite.createTest(TestSuite.java:54)
at junit.framework.TestSuite.addTestMethod(TestSuite.java:280)
at junit.framework.TestSuite.<init>(TestSuite.java:140)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestLoader.getTest(JUnit3TestLoader.java:102)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestLoader.loadTests(JUnit3TestLoader.java:59)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:445)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
... 17 more

I googled it and on another forum they said that you needed two additional .jars named, slf4j-api-1.5.6.jar and slf4j-jcl-1.5.6.jar, which I also downloaded and added to the buildpath.
Sadly, it still doesn't work. Any ideas on why?

Regards,
Alia

You need the Apache Commons Logging library in the classpath; that's where the "org/apache/commons/logging/LogFactory" class is.

Right, forgive me for being so green, asking all these silly questions *smiles*
But how do I get it?
Do I download it from http://commons.apache.org/downloads/download_logging.cgi? And if so, should I choose the binary one or the source?
And, how do I add a library to my classpath? I can't remember every doing it, not by myself anyhow.

Thanks again!

Yes, that's where you get it; you need the binary build. The file is named common-logging-1.1.1.jar or something like that.

You put it together with the other jar files. You mentioned above that you added jar files for MySQL, DBUnit etc. - just do whatever you did with those file with this one as well.

Right thanks!
And there I got another exception to add to the list.
At

org.dbunit.dataset.DataSetException: java.net.MalformedURLException
at org.dbunit.dataset.xml.FlatXmlProducer.produce(FlatXmlProducer.java:370)
at org.dbunit.dataset.CachedDataSet.<init>(CachedDataSet.java:97)
at org.dbunit.dataset.CachedDataSet.<init>(CachedDataSet.java:81)
at org.dbunit.dataset.xml.FlatXmlDataSet.<init>(FlatXmlDataSet.java:303)
at org.dbunit.dataset.xml.FlatXmlDataSet.<init>(FlatXmlDataSet.java:290)
at com.jayway.konfbooking.test.dbUnit.TestDbUnit.getDataSet(TestDbUnit.java:24)
at org.dbunit.DatabaseTestCase.setUp(DatabaseTestCase.java:150)
at junit.framework.TestCase.runBare(TestCase.java:132)
at junit.framework.TestResult$1.protect(TestResult.java:110)
at junit.framework.TestResult.runProtected(TestResult.java:128)
at junit.framework.TestResult.run(TestResult.java:113)
at junit.framework.TestCase.run(TestCase.java:124)
at junit.framework.TestSuite.runTest(TestSuite.java:232)
at junit.framework.TestSuite.run(TestSuite.java:227)
at org.eclipse.jdt.internal.junit.runner.junit3.JUnit3TestReference.run(JUnit3TestReference.java:130)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)
Caused by: java.net.MalformedURLException
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at java.net.URL.<init>(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLEntityManager.setupCurrentEntity(Unknown Source)
at com.sun.org.apache.xerces.internal.impl.XMLVersionDetector.determineDocVersion(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(Unknown Source)
at com.sun.org.apache.xerces.internal.jaxp.SAXParserImpl$JAXPSAXParser.parse(Unknown Source)
at org.dbunit.dataset.xml.FlatXmlProducer.produce(FlatXmlProducer.java:357)
... 19 more

This is getting tiresome *smiles*
I wonder why they don't make tutorials that actually work.
Some info on which libraries were needed would have saved both me and you alot of trouble. Ohwell.
Sod's law and human factor at it's very best. *grins*

So, what does that mean? MalformedURLException?

Thanks for bearing with me!

Where (in which directory) do you keep the file "input.xml"?

It's in the same folder/package as the test class.
And a collegue of mine found where the problem was,
he removed the .getClassLoader() from the code-snippet i showed you in my previous reply, and now it works!

Thank you so much for your help!
Finally I can move on and do some real testing.

Regards,
Alia

Any time when you see this exception "org.dbunit.dataset.DataSetException: java.net.MalformedURLException" this is an indication that something wrong with the dataset file (input.xml) that we are referring.
There could be many reasons - Name of the file, path of the file, location of the file.

In my case, i had changed the file name from input.xml to source_test.xml and forgot to change the referece to this in the test class. So every thing messed up.
started getting the "org.dbunit.dataset.DataSetException: java.net.MalformedURLException".. after one hour i understood the reason.

Hope this is useful.