About Frameworks, Algorithms and Software Engineering

Nov. 30, 2019

Deep Assertions

Occasionally unit testing is more complex than with simple types, e.g with

  • results from webservice interfaces (REST/SOAP)
  • orm-mapped database results
  • parse trees
  • graphs or trees in general

Such types are deeply (or recusively) nested and thus not easily validated. It is easier when using the right tool - e.g. with the IsEquivalent-Matcher of XrayInterface

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Jan. 24, 2019

Test Generation in Java - an Overview

The time has come to summarize my research on test generation in Java. One year ago I started with a presentation “Testgeneration in Java” at several conferences and meanwhile I can present the essence of these presentations …

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Sept. 15, 2018

Test Generators - State of Technology

Maybe an overview of testgenerators is interesting to you. A quite complete list could be found on the summary of Zoltán Micskei about Code-based test generation. Most of the listed projects are mainly of academic value - fine for example code, yet not fit for practice.

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Mai 4, 2018

Regular Expressions in Java

I used Java regular expressions (java.util.regex) for years uncritically. University taught me that regular expression are efficient.

Some day in my project I had the challenge to search a large amount of words (>1.000) in a large number of documents (>10.000). I remembered college and instead of searching each word in each document. I decided to search in each document for the regular expression <Word1>|<Word2>|...|<Word1000>. That should have been far more efficient than searching each word in each document … However, regular expression is not regular expression and the fast automatons known to me from college are not the same that are provided by Java.

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Apr. 2, 2018

Exact String Matching in Practice

Initially I was interested in string search from an academic view point - just understand the algorithm and be able to implement it. After this passion culminated in the project (StringSearchAlgorithms), I began to compare it to others …

It became obvious that many algorithms worked in theory, but were slow or even failing in practice. Actually most academic algoirthms on string search are optimized for a certain situation dependent on:

  • processors
  • encoding
  • programming languages and APIs

The following sections describe the challenges string search is confronted to in practice.

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Mai 29, 2017

Testrecorder – Next Steps

After Presenting at Karlsruher Entwicklertag it is time to write a few words about the future of Testrecorder … Testrecorder is a Java tool vor recording runtime situations. Recording means, that we intercept method invocation and capture the state before and after the invocation. From this captured state we generate JUnit-tests.

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Okt. 12, 2016

Naming of Interfaces and Implementations

Many of you are probably familiar with code containing an interface FormDataValue and implementation classes FormDataValueImpl. However I received consent on my complacent criticism, accompanied by an excuse like: “Our team decided not to follow a naming condition like e.g. IFormDataValue.”

I feel my criticism was misunderstood? There are almost always more than two options in naming classes. Why do some teams only find these two? I will try to analyze the problem more deeply …

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Aug. 10, 2016

String Search in Java (using the JDK-API)

String search is a common problem, appearing every time we check that a string is contained in another. The JDK Standard API provides some basic functionality for this, yet there are more efficient algorithms for larger patterns and larger texts.

In this posting I present an overview over the string searching features of the Java API, starting with a short definition of string searching and ending with an overview of libraries that provide more features for string searching (more details will follow in later postings).

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Mai 21, 2016

Accessing Private Fields and Methods with XRayInterface

This posting is about accessing private fields and methods, by adopting a foreign interface to a given java class (not already implementing the given interface). Why? Yet, in my former posting about Repairing Legacy Code I mentioned the challenge of accessing hidden state (private fields) before and after method invocations.

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März 27, 2016

Repairing Legacy Code - Automatically

Many Projects already use automated regression testing. Unfortunately we cannot rely on this in situations that afford them most, for maintaining foreign (untested) legacy code. Here I do not only wish for automated regression tests, I also wish for automated test generators. Why does such a tool not exist?

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My Talks

I was speaker at several conferences. A list of my talks are found at Talks.

My Projects

I host some Open Source Projects on Github, my most successful projects have their own website: