On the Effectiveness of Unit Tests in Test-driven Development

Background: Writing unit tests is one of the primary activities in test-driven development. Yet, the existing reviews report few evidence supporting or refuting the effect of this development approach on test case quality. Lack of ability and skills of developers to produce sufficiently good test cases are also reported as limitations of applying test-driven development in industrial practice. Objective: We investigate the impact of test-driven development on the effectiveness of unit test cases compared to an incremental test last development in an industrial context. Method: We conducted an experiment in an industrial setting with 24 professionals. Professionals followed the two development approaches to implement the tasks. We measure unit test effectiveness in terms of mutation score. We also measure branch and method coverage of test suites to compare our results with the literature. Results: In terms of mutation score, we have found that the test cases written for a test-driven development task have a higher defect detection ability than test cases written for an incremental test-last development task. Subjects wrote test cases that cover more branches on a test-driven development task compared to the other task. However, test cases written for an incremental test-last development task cover more methods than those written for the second task. Conclusion: Our findings are different from previous studies conducted at academic settings. Professionals were able to perform more effective unit testing with test-driven development. Furthermore, we observe that the coverage measure preferred in academic studies reveal different aspects of a development approach. Our results need to be validated in larger industrial contexts.Istanbul Technical University Scientific Research Projects (MGA-2017-40712), and the Academy of Finland (Decision No. 278354)

Empirical Investigation on Agile Methods Usage: Issues Identified from Early Adopters in Malaysia

Agile Methods are a set of software practices that can help to produce products faster and at the same time deliver what customers want. Despite the benefits that Agile methods can deliver, however, we found few studies from the Southeast Asia region, particularly Malaysia. As a result, less empirical evidence can be obtained in the country making its implementation harder. To use a new method, experience from other practitioners is critical, which describes what is important, what is possible and what is not possible concerning Agile. We conducted a qualitative study to understand the issues faced by early adopters in Malaysia where Agile methods are still relatively new. The initial study involves 13 participants including project managers, CEOs, founders and software developers from seven organisations. Our study has shown that social and human aspects are important when using Agile methods. While technical aspects have always been considered to exist in software development, we found these factors to be less important when using Agile methods. The results obtained can serve as guidelines to practitioners in the country and the neighbouring regions

Dynamics of railway freight vehicles

This paper summarises the historical development of railway freight vehicles and how vehicle designers have tackled the difficult challenges of producing running gear which can accommodate the very high tare to laden mass of typical freight wagons whilst maintaining stable running at the maximum required speed and good curving performance. The most common current freight bogies are described in detail and recent improvements in techniques used to simulate the dynamic behaviour of railway vehicles are summarised and examples of how these have been used to improve freight vehicle dynamic behaviour are included. A number of recent developments and innovative components and sub systems are outlined and finally two new developments are presented in more detail: the LEILA bogie and the SUSTRAIL bogie

Some changes of hydraulics conditions along a river engineered part of the Cedron Stream in the Beskid Sredni mountains

W pracy przedstawiono skutki zabudowy hydrotechnicznej potoku i jej wpływ na zmianę wybranych parametrów hydraulicznych koryta. Reżim przepływu w korytach jest charakteryzowany przez rozkład prędkości wody w pionach hydrometrycznych, wartość naprężeń stycznych na dno, wartość mocy strumienia oraz wartość mocy jednostkowej strumienia. Założono sześć przekrojów poprzecznych na potoku Cedron w Beskidzie Średnim, w których zostały wykonane pomiary prędkości na kilku głębokościach nad dnem przed i po regulacji, a następnie obliczono naprężenia styczne na dnie cieku, całkowite i jednostkowe moce strumienia i przeprowadzono analizę obliczonych parametrów.The paper presents the effects of applied river engineering works and its influence on the changes of chosen hydraulics parameters along a reach of the mountainous stream. It was done by presenting the regime of the stream before and after river engineering works. The key parameters used for the hydraulics analysis were: stream velocity, shear stresses, stream power and finally the unit stream power. The research area was located in Polish Carpathians in the Beskid Sredni Mountains. The research stream is called the Cedron and the research reach is located close to Radziszow municipality around 30 kilometers from Krakow. The research was carried out in 2003 (before the river engineering works, after the major flooding in the region) and in 2004 after finishing river training works, which were mostly targeted to stop the bottom of the river and its banks from erosion. To carry on the research 6 cross sections were chosen where detailed velocities of running water were measured in the velocity profiles. Later the rest of analyzed hydraulics parameters such as stream power and shear stresses were calculated. The results were presented in graphical manner (fig. 1-4) and analyzed. In final conclusions it was pointed out, that all river training works hale the inevitable influence on river regime changes, thus after river engineering works which had a place on the left bank of the Cedron river (where special river bank protection gabions were installed) the shear stresses acting on the river bed and banks were stabilized

Wpływ dodatku osadu dennego do gleby na plon i skład chemiczny kukurydzy

A two-year pot experiment was conducted to assess the effect of bottom sediment, used as a supplement to the light soil, on the yield and contents of macroelements in maize. The bottom sediment was added to light soil in the proportion of 5 and 10 %. The material was classified to a group of ordinary silt deposit. Moreover, the analyzed sediment revealed alkaline reaction, organic matter content of 25.8 g kg-1, low content of bioavailable phosphorus and potassium and natural content of heavy metals. After the experiment completion the amount of maize dry matter yield was assessed. The contents of minerals in the plant mass was determined after dry mineralization and the ash dissolving in HNO3 (1:3), K, Mg, Ca, and Na were determined using AAS and P with ICP-AES technique. Nitrogen content was determined by means of Kjeldahl distillation method. The experiment demonstrated a positive effect of bottom sediment supplement to light soil on the amount of produced maize biomass. The greatest maize biomass was obtained on the treatment with a 5 % admixture of bottom sediment. However, the plant shoot biomass did not meet the criteria for good quality fodder because of too low contents of most macroelements. It was found that the analyzed bottom sediment may be used as an admixture to light and acid soils to improve their productivity, owing to a considerable share of silt and clay fractions in its composition, neutral reaction and low content of heavy metals. However, each agricultural application of bottom sediment requires a supplementary mineral fertilization because of low contents of fertilizer elements in the sediment and in the obtained maize biomass.Celem dwuletniego doświadczenia wazonowego była ocena wpływu osadu dennego stosowanego jako dodatek do gleby lekkiej na plon i zawartość makrślementów w kukurydzy. Osad denny dodano do gleby lekkiej w ilości 5 i 10 %. Materiał ten zakwalifikowano do grupy utworów pyłowych zwykłych i charakteryzował się on odczynem zasadowym, zawartością materii organicznej wynoszącą 25,8 g kg-1, niską zawartością przyswajalnego fosforu i potasu oraz naturalną zawartością metali ciężkich. Po zakończeniu doświadczenia określono wielkość plonu suchej masy kukurydzy. Zawartość składników mineralnych w materiale roślinnym oznaczono po suchej mineralizacji i roztworzeniu popiołu w HNO3 (1:3), techniką AAS (K, Mg, Ca, Na) oraz ICP-EAS (P). Zawartość N oznaczono metodą destylacyjną Kjeldahla. Stwierdzono pozytywny wpływ osadu dennego dodanego do gleby lekkiej na plon biomasy kukurydzy. Największą biomasę rośliny uzyskano w obiekcie z dodatkiem osadu w ilości 5 %. Nadziemna biomasa roślinna nie spełniała jednak kryteriów dla paszy dobrej jakości, ze względu na zbyt małe zawartości większości makrślementów. Stwierdzono, że badany osad denny ze względu na duży udział frakcji pylastych i ilastych w swoim składzie, obojętny odczyn i małą zawartość metali ciężkich może być stasowany jako dodatek do gleb lekkich i kwaśnych w celu poprawy ich produkcyjności. W rolniczym wykorzystaniu osadu dennego należy jednak zastosować uzupełniające nawożenie mineralne z powodu niskiej zawartości pierwiastków nawozowych w osadzie oraz biomasie kukurydzy

The Importance of the Correlation in Crossover Experiments

Context: In empirical software engineering, crossover designs are popular for experiments comparing software engineering techniques that must be undertaken by human participants. However, their value depends on the correlation (r) between the outcome measures on the same participants. Software engineering theory emphasizes the importance of individual skill differences, so we would expect the values of r to be relatively high. However, few researchers have reported the values of r. Goal: To investigate the values of r found in software engineering experiments. Method: We undertook simulation studies to investigate the theoretical and empirical properties of r. Then we investigated the values of r observed in 35 software engineering crossover experiments. Results: The level of r obtained by analysing our 35 crossover experiments was small. Estimates based on means, medians, and random effect analysis disagreed but were all between 0.2 and 0.3. As expected, our analyses found large variability among the individual r estimates for small sample sizes, but no indication that r estimates were larger for the experiments with larger sample sizes that exhibited smaller variability. Conclusions: Low observed r values cast doubts on the validity of crossover designs for software engineering experiments. However, if the cause of low r values relates to training limitations or toy tasks, this affects all Software Engineering (SE) experiments involving human participants. For all human-intensive SE experiments, we recommend more intensive training and then tracking the improvement of participants as they practice using specific techniques, before formally testing the effectiveness of the techniques