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Python: Writing test to verify command line arguments

May 28, 2019 Kenneth Holter Comments 0 Comment

I wrote a small Python script that will be executed from the command line. After finishing the tests to verify the business logic, I decided to test the command line arguments as well, just to make sure they’re parsed correctly and passed to their appropriate places in the business logic code. Initially I was thinking I needed to write a test that executes the actual command line such as python3 myscript.py –argument=value, but as this is neither appropriate nor really…

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SQLAlchemy + Database Link => ORA-04054

April 17, 2019 Kenneth Holter Comments 0 Comment

I’ve got this SQLAclhemy table definition that describes a table I’ll be accessing over an Oracle database link: I first created a database link such as this: In SQLAlchemy, access a table column (in a query) via that link would look like tihs I turns out that SQLAlchemy with Oracle database links isn’t a very good match, and easily results in errors such as this: To work around this issue, I created a synonym like this: Now, accessing the table…

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Running Oracle in Docker for development and testing

April 15, 2019 Kenneth Holter Comments 0 Comment

I’m working on a Python based microservice that needs to communicate with an Oracle database. My development environment consist only of my laptop, so to do some real testing I decided to spin up Oracle in a Docker container on my laptop. For me, the process of getting things up and running wasn’t very straight forward for an Oracle newbie as myself, so I though I’d share my setup in case others may benefit from it. Let’s start with my…

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Extending business logic functions in unit tests

April 13, 2019 Kenneth Holter Comments 0 Comment

We have a database view, from now on referred to as View, that lists users we need to send an email to, and when we’ve sent the user an email we acknowledge this by updating the corresponding user in a database table (which is one of the tables the above mentioned database view is build from), from now on referred to as Table. For my unit tests I needed to emulate this behavior. I found that by extending the database…

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Using the factory pattern to create different emails based on input parameters

April 11, 2019 Kenneth Holter Comments 0 Comment

I wrote a small service that takes an MQ message as input, and based on the contents of the message creates and sends an email. The different types of incoming MQ messages require different types of emails to be created, so I needed a maintainable way to create different emails. For my use case, I found that the factory pattern was a good fit. Consider this code: My business logic code that uses this code then get to be as…

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Add list of users to AD group using PowerShell

April 7, 2019 Kenneth Holter Comments 0 Comment

Here’s a very simple PowerShell script that takes as input a list of email addresses, and add the corresponding AD users to a defined AD group.

Spying on Python functions

February 19, 2019 Kenneth Holter Comments 0 Comment

I was writing test code for a Python project, and needed to spy on the functions of one of the main object’s, called “server”, object instances called “rest_client”. By simply replacing the “rest_client” instance with a mock that passes the actual call to the wrapped object, I’m able to execute the production code of “rest_client” while later on making assertions.

Developing .NET applications without installing .NET SDK

November 29, 2018 Kenneth Holter Comments 0 Comment

I recently developed a small .NET application. I considered installing the .NET SDK on my laptop (on which I were to develop the .NET application), but was unsure of which version I would need, and how I would potentially downgrade the SDK version if needed. Instead of installing the SDK on my laptop, I decided to run the SDK inside a Docker container. This way I could easily switch between SDK versions if needed, as all I’d have to do…

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Docker build fails with “no matching manifest for unknown in the manifest list entries”

November 22, 2018 Kenneth Holter Comments 0 Comment

I recently got this error when trying to build a Windows container (specifically microsoft/dotnet-framework:4.7.2-sdk) on my Windows 10 laptop: no matching manifest for unknown in the manifest list entries I was surprised that I couldn’t build Windows containers on my Windows laptop, but then I recalled that Docker for Windows let you choose between running Linux containers or Windows containers. As I until now had exclusively ran Linux containers, my Docker was set up to run Linux containers, but configuring Docker to…

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Patching Python instance methods

November 10, 2018 Kenneth Holter Comments 0 Comment

I’m working on a project in which one of our services need to publish messages to a RabbitMQ exchange. Consider this code excerpt from the message queue client:

# file: mq_client.py
import pika

class MQ_Client():
    connection = None
    channel = None
    exchange_name="my_exchange"

    def connect(self):
        self.connection = pika.BlockingConnection(pika.ConnectionParameters(host="mq_server")
        self.channel = connection.channel()

    def publish(self, message):

        properties = pika.BasicProperties(content_type='text/json', delivery_mode=1)

        if self.channel.basic_publish(exchange=self.exchange_name, routing_key='', properties=properties, body=message):
            log.info("Successfully published this message to exchange \"" + self.exchange_name + "\": " + message)
        else:
            log.error("Failed to publish message \"" + message + "\" to the exchange \"" + self.exchange_name + "\"!")
            raise Exception("Failed to publish message to the queue.")

# file: mq_client.py

import pika

class MQ_Client():

connection = None

channel = None

exchange_name="my_exchange"

def connect(self):

self.connection = pika.BlockingConnection(pika.ConnectionParameters(host="mq_server")

self.channel = connection.channel()

def publish(self, message):

properties = pika.BasicProperties(content_type='text/json', delivery_mode=1)

if self.channel.basic_publish(exchange=self.exchange_name, routing_key='', properties=properties, body=message):

log.info("Successfully published this message to exchange \"" + self.exchange_name + "\": " + message)

else:

log.error("Failed to publish message \"" + message + "\" to the exchange \"" + self.exchange_name + "\"!")

raise Exception("Failed to publish message to the queue.")

In my unit tests I wanted to verify that an unsuccessful attempt to publish the message, would cause trigger an exception to be thrown. To test this, I needed basic_publish to return False. At first I found it tricky to patch instance methods such as basic_publish , but after coming across this excellent…

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