Wednesday, 28 June 2017

Tell, don't ask

More than twelve years ago Tim Joyce passed on some programming wisdom:

With programs tell don't ask, vice versa for people.

This was a bit abstract for me at the time but last night it came back to me as what is wrong with the code I am currently working on. We store our application configuration in a table in the system's target database and whenever some configuration is needed it is looked up in the database. There was no problem with this approach when the code was written because JUnit had not been invented and testing was not the main part of our discipline. However to write a test we would need a database present, which is an obstacle to fast, distinct, unit tests and has been a blocker to writing tests.

Noncompliant Code Example

public class Example { 
  private String path;
  public void logPath() {
    try {
      path = CachedSystemParameter.getInstance().
                 getParameterValue("PATH");
    } catch (SystemParameterException e) {
      logger.error("[BUSINESS] Error while retrieving system parameter PATH", e);
    }
    logger.info("Path: " + path);
  }
}

Compliant Code Example

By adding sftpPath to the class constructor we can test the business logic without the need for a database fixture.
public class Example { 

  private String path;

  public Example() { 
    this(CachedSystemParameter.getInstance().
                 getParameterValue("PATH"));
  }

  public Example(String path) { 
    this.path = path;
  } 

  public void logPath() {
    logger.info("Path: " + path);
  }
}

Thursday, 4 May 2017

Testing java slf4j over log4j logging in JUnit using SLF4J Test

Testing logging on failure paths has two problems:

  • It is hard to get the log message text
  • The logger outputs to the test log
The first leads to compromises eg verifying only that a message was logged, the second makes you, the programmer, think an error has occurred when the tests in fact passed.

Code to test


public class Sut { 
    public String perform() {
        getLog().debug("In perform");
        return "Hello world";
    }
}

My clunky PowerMock Solution

My approach was problematic as it required the use of PowerMock which is as powerful as nitroglycerin.

Test Code


@RunWith(PowerMockRunner.class)
@PrepareForTest({LoggerFactory.class})
public class SutTest {

    @Test
    public void testPerform() {
        mockStatic(LoggerFactory.class);
        Logger mockLog = mock(Logger.class);
        when(LoggerFactory.getLogger(any(Class.class))).thenReturn(mockLog);

        assertEquals("Hello world", new Sut().perform());
        verify(mockLog, times(1)).debug(startsWith("In perform"));
    }
}

Elegant SLF4j Test Solution

The slf4j-test project by RobElliot266 provides a logger which stores messages and so can be asserted against.

POM Setup

Add the following to your dependencies


        <dependency>
            <groupId>uk.org.lidalia</groupId>
            <artifactId>slf4j-test</artifactId>
            <version>1.1.0</version>
            <scope>test</scope>
        </dependency>

To ensure that this logger is used during tests only and that it takes precedence over the production logger in the test class path ensure the test logger is the first logger mentioned in the dependencies block and has a test scope.

As an additional measure you can explicitly exclude the production logger from the test class path:


        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <version>2.18.1</version>
            <configuration>
                <classpathDependencyExcludes>
                    <classpathDependencyExcludes>org.slf4j:slf4j-jdk14</classpathDependencyExcludes>
                </classpathDependencyExcludes>
            </configuration>
        </plugin>

Test Code


public class SutTest {
  @Test
  public void testPerform() {
    assertEquals("Hello world", new Sut().perform());
    assertEquals("Testing", logger.getLoggingEvents().get(0).getMessage());
  }
}

Much thanks to RobElliot266 for an neat solution to a problem that has been bugging me for a while.

Saturday, 18 March 2017

A stack chart of any CSV url

Stack chart.

Thursday, 15 December 2016

Migrate MelatiSite from CVS to github

Re-visiting http://tim-pizey.blogspot.co.uk/2011/10/cvs-to-github.html (why did I not complete this at the time?)

Following How to export revision history from mercurial or git to cvs?

On hanuman I created an id file git_authors mapping cvs ids to github name, email format for all contributors:

timp=Tim Pizey<timp@paneris.org>
then create a repository on github (melati in this example, I already have uploaded my ssh public key for this machine)
cd ~
git cvsimport -d /usr/cvsroot -C MelatiSite -r cvs -k -A git_authors MelatiSite

cd melati
echo A jdbc to java object relational mapping system. 1999-2011 > README.txt
git add README.txt
git commit -m "Initial" README.txt
git remote add origin git@github.com:timp21337/melati.git
git push -u origin master
See https://github.com/timp21337/melati.

Saturday, 14 May 2016

JaCoCo UnitTest and IntegrationTest Configuration Example

The number of ways in which Maven, Surefire, Failsafe, Jacoco, Selenium and Jetty can be mis-configured is enormous.

I have explored this space and honestly this is the only one which worked!

JaCoCo UnitTest and IntegrationTest Configuration Example on github with results on a Maven generated github.io site.

Wednesday, 16 March 2016

CentOS setup on VirtualBox

Once you have Networking working there is still a long way to go.

yum groupinstall "Development Tools"
yum install kernel-devel
yum install kde-workspace
yum group install "X Window System"
yum groupinstall "Fonts" 
yum install gdm

Now we can login without a GUI but startx when one is needed.

Installing Guest Additions

The guest Centos is a stock distribution, you have to tell it that it is inside VirtualBox.

Make the additions visible to the guest:

In the "Devices" menu in the virtual machine's menu bar, VirtualBox has a handy menu item named "Insert Guest Additions CD image", which mounts the Guest Additions ISO file inside your virtual machine.

yum install dkms
mkdir -p /media/cdrom
# Note change from /dev/scd0 in CentOS6
mount /dev/sr0 /media/cdrom 
sh /media/cdrom/VBoxLinuxAdditions.run

We are now able to move the mouse seamlessly between our guest and host and window systems understand each other.

Sharing files between the host and guest

In the host (Windows) create C:\vbshared and using the VirtualBox interface share this with the guest. In the guest:

mkdir /vbshared
mount -t vboxsf vbshared /vbshared

it will be visible as /vbshared/ from inside the guest.

Enable networking in VirtualBox Centos Client

The CentOS 7 iso does not enable networking during the installation, unlike Ubuntu. So your shiny new CentOS cannot get to the outside world.

Based on Stack Overflow - CentOS 7 VirtualBox no internet access.

Add the following to /etc/sysconfig/network-scripts/ifcfg-enp0s3

DNS1=8.8.8.8
DNS2=8.8.4.4
# Note this was set to no
ONBOOT=yes