Impact of test-driven development on productivity, code and tests: A controlled experiment

Context

Test-driven development is an approach to software development, where automated tests are written before production code in highly iterative cycles. Test-driven development attracts attention as well as followers in professional environment; however empirical evidence of its superiority regarding its effect on productivity, code and tests compared to test-last development is still fairly limited. Moreover, it is not clear if the supposed benefits come from writing tests before code or maybe from high iterativity/short development cycles.

Objective

This paper describes a family of controlled experiments comparing test-driven development to micro iterative test-last development with emphasis on productivity, code properties (external quality and complexity) and tests (code coverage and fault-finding capabilities).

Method

Subjects were randomly assigned to test-driven and test-last groups. Controlled experiments were conducted for two years, in an academic environment and in different developer contexts (pair programming and individual programming contexts). Number of successfully implemented stories, percentage of successful acceptance tests, McCabe’s code complexity, code coverage and mutation score indicator were measured.

Results

Experimental results and their selective meta-analysis show no statistically significant differences between test-driven development and iterative test-last development regarding productivity (χ²(6) = 4.799, p = 1.0, r = .107, 95% CI (confidence interval): −.149 to .349), code complexity (χ²(6) = 8.094, p = .46, r = .048, 95% CI: −.254 to .341), branch coverage (χ²(6) = 13.996, p = .059, r = .182, 95% CI: −.081 to .421), percentage of acceptance tests passed (one experiment, Mann-Whitney U = 125.0, p = .98, r = .066) and mutation score indicator (χ²(4) = 3.807, p = .87, r = .128, 95% CI: −.162 to .398).

Conclusion

According to our findings, the benefits of test-driven development compared to iterative test-last development are small and thus in practice relatively unimportant, although effects are positive. There is an indication of test-driven development endorsing better branch coverage, but effect size is considered small.     

Antioxidant and antimicrobial activity of guarana seed extracts

The antioxidant and antibacterial activities of guarana (Paullinia cupana) seed extracts were determined. The seeds were extracted with water, methanol, 35% acetone and 60% ethanol at room (T_R) and at boiling (T_B) temperature of solvent.     

The Relationship between COVID-19 and Hypothalamic–Pituitary–Adrenal Axis: A Large Spectrum from Glucocorticoid Insufficiency to Excess—The CAPISCO International Expert Panel

Coronavirus disease 2019 (COVID-19) is a highly heterogeneous disease regarding severity, vulnerability to infection due to comorbidities, and treatment approaches. The hypothalamic–pituitary–adrenal (HPA) axis has been identified as one of the most critical endocrine targets of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that might significantly impact outcomes after infection. Herein we review the rationale for glucocorticoid use in the setting of COVID-19 and emphasize the need to have a low index of suspicion for glucocorticoid-induced adrenal insufficiency, adjusting for the glucocorticoid formulation used, dose, treatment duration, and underlying health problems. We also address several additional mechanisms that may cause HPA axis dysfunction, including critical illness-related corticosteroid insufficiency, the direct cytopathic impacts of SARS-CoV-2 infection on the adrenals, pituitary, and hypothalamus, immune-mediated inflammations, small vessel vasculitis, microthrombotic events, the resistance of cortisol receptors, and impaired post-receptor signaling, as well as the dissociation of ACTH and cortisol regulation. We also discuss the increased risk of infection and more severe illness in COVID-19 patients with pre-existing disorders of the HPA axis, from insufficiency to excess. These insights into the complex regulation of the HPA axis reveal how well the body performs in its adaptive survival mechanism during a severe infection, such as SARS-CoV-2, and how many parameters might disbalance the outcomes of this adaptation.     

Light fastness and high‐temperature stability of thermochromic printing inks

Thermochromic printing inks are known for their low stability under the influence of various external conditions, but the consequences of the phenomenon on dynamic colorimetric properties have not yet been analysed. In this work, thermochromic prints were exposed to light and heated at two different temperatures, 150 and 200 °C, for varying time periods. The changes to the dynamic colour properties of the samples were described. It was found that both exposure to light and heating to high temperatures degrade the dynamic properties of thermochromic inks; however, they have different effects on the colour hysteresis. The corresponding loops contract with light exposure and heating, which is best described by the area of the entire colour loop. Exposure to light broadens the corresponding loop, while heating makes it narrower. The chemical stability of inks after exposure was also analysed by forced oxidation applying weakly ionised oxygen plasma. Stability of thermochromic samples is a combined effect of the binder, the polymeric shell and the active core inside the pigment capsules. The results show that poor stability against light and high temperatures has different origins.     

Laccase-initiated reaction between phenolic acids and chitosan

Phenolic acids are known to possess antioxidant activities whilst chitosan is a biocompatible polymer with antibacterial activity against a broad spectrum of bacteria. Merging both types of molecules could therefore provide several potential applications. In this work, antioxidant properties of phenolic acid–functionalized-chitosan were investigated after being prepared from structurally-different phenolic acids (caffeic and gallic acids) and chitosan using the laccase from Trametes versicolor as the reaction initiator. A laccase-mediated oxidation kinetic of phenolic acids was monitored by UV–vis spectroscopy and cyclic voltammetry, as well as spin-trapping electron paramagnetic resonance spectroscopy (ST-EPR). The pH was shown to have a significant effect on the degree of phenolic acid self-polymerization, indicating the involvement of phenolate anions within the formations of coupled polyphenol products, and their functionalities, i.e. antioxidant activity. All the phenolic acid-functionalized-chitosans displayed greatly improved ABTS radical cation scavenging capacities, compared with the untreated chitosan.     

Electrochromism in composite WO<Subscript>3</Subscript>–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> thin films synthesized by spray pyrolysis technique

Composite WO₃–Nb₂O₅ thin films were deposited on the glass and fluorine-doped tin oxide (FTO)-coated glass substrates using simple and inexpensive spray pyrolysis technique. The process parameters, like nozzle-to-substrate distance, spray rate, concentration of sprayed solution, etc., were optimized to good quality films. The films were characterized for the structural, morphological, optical, and electrochromic properties. Structural and morphological characterizations of the films were carried out using scanning electron microscopy and X-ray diffraction techniques. Electrochemical properties of the Composite WO₃–Nb2O₅ thin films were further studied using cyclic-voltammetry, chronoamperometry, chronocoulometry, and electrochemical Impedance spectroscopy.     

Conformational Preferences and Antiproliferative Activity of Peptidomimetics Containing Methyl 1′-Aminoferrocene-1-carboxylate and Turn-Forming Homo- and Heterochiral Pro-Ala Motifs

The concept of peptidomimetics is based on structural modifications of natural peptides that aim not only to mimic their 3D shape and biological function, but also to reduce their limitations. The peptidomimetic approach is used in medicinal chemistry to develop drug-like compounds that are more active and selective than natural peptides and have fewer side effects. One of the synthetic strategies for obtaining peptidomimetics involves mimicking peptide α-helices, β-sheets or turns. Turns are usually located on the protein surface where they interact with various receptors and are therefore involved in numerous biological events. Among the various synthetic tools for turn mimetic design reported so far, our group uses an approach based on the insertion of different ferrocene templates into the peptide backbone that both induce turn formation and reduce conformational flexibility. Here, we conjugated methyl 1′-aminoferrocene-carboxylate with homo- and heterochiral Pro-Ala dipeptides to investigate the turn formation potential and antiproliferative properties of the resulting peptidomimetics 2–5. Detailed spectroscopic (IR, NMR, CD), X-ray and DFT studies showed that the heterochiral conjugates 2 and 3 were more suitable for the formation of β-turns. Cell viability study, clonogenic assay and cell death analysis showed the highest biological potential of homochiral peptide 4.     

The effects of solvents on the formation of sol–gel-derived Bi12SiO20 thin films

The sol–gel method was used to synthesize Bi₁₂SiO₂₀ thin films. Two synthesis routes with two different solvents, i.e., 2-ethoxyethanol and acetic acid, were used and compared. Thin films were deposited onto Pt/TiO₂/SiO₂/Si substrates by spin-coating at 3000 rpm and annealed at 700 °C for 1 h. A different coordination of the bismuth ion was observed in the sols prepared with acetic acid (AcOH), and as a result, stable sols were formed with a shorter gelation time t_G = 84 h (c = 0.76 M), when compared with the sols prepared from 2-ethoxyethanol (EtoEtOH) t_G = 580 h (c = 0.76 M). The microstructures of the Bi₁₂SiO₂₀ thin films prepared from sols using EtoEtOH were homogeneous and dense. On the other hand, a porous microstructure was observed for the Bi₁₂SiO₂₀ thin films deposited from the sol in which AcOH was used as the solvent.     

Manganese Functionalized Silicate Nanoparticles as a Fenton‐Type Catalyst for Water Purification by Advanced Oxidation Processes (AOP)

Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X‐ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H₂O₂ to reactive hydroxyls and, unlike manganese in Mn₃O₄ or Mn₂O₃ nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost‐effective, and possess superior efficiency for the decomposition of H₂O₂ to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.     

Bidirectional Artificial Neural Networks for Mobile‐Phone Fraud Detection

We propose a system for mobile‐phone fraud detection based on a bidirectional artificial neural network (bi‐ANN). The key advantage of such a system is the ability to detect fraud not only by offline processing of call detail records (CDR), but also in real time. The core of the system is a bi‐ANN that predicts the behavior of individual mobile‐phone users. We determined that the bi‐ANN is capable of predicting complex time series (Call_Duration parameter) that are stored in the CDR.