University of Luxembourg

About: University of Luxembourg is a education organization based out in Luxembourg, Luxembourg. It is known for research contribution in the topics: Context (language use) & Computer science. The organization has 4744 authors who have published 22175 publications receiving 381824 citations.

Trivial compiler equivalence: a large scale empirical study of a simple, fast and effective equivalent mutant detection technique

Abstract: Identifying equivalent mutants remains the largest impediment to the widespread uptake of mutation testing. Despite being researched for more than three decades, the problem remains. We propose Trivial Compiler Equivalence (TCE) a technique that exploits the use of readily available compiler technology to address this long-standing challenge. TCE is directly applicable to real-world programs and can imbue existing tools with the ability to detect equivalent mutants and a special form of useless mutants called duplicated mutants. We present a thorough empirical study using 6 large open source programs, several orders of magnitude larger than those used in previous work, and 18 benchmark programs with hand-analysis equivalent mutants. Our results reveal that, on large real-world programs, TCE can discard more than 7% and 21% of all the mutants as being equivalent and duplicated mutants respectively. A human- based equivalence verification reveals that TCE has the ability to detect approximately 30% of all the existing equivalent mutants.

Blockchain-Based, Decentralized Access Control for IPFS

Abstract: Large files cannot be efficiently stored on blockchains. On one hand side, the blockchain becomes bloated with data that has to be propagated within the blockchain network. On the other hand, since the blockchain is replicated on many nodes, a lot of storage space is required without serving an immediate purpose, especially if the node operator does not need to view every file that is stored on the blockchain. It furthermore leads to an increase in the price of operating blockchain nodes because more data needs to be processed, transferred and stored. IPFS is a file sharing system that can be leveraged to more efficiently store and share large files. It relies on cryptographic hashes that can easily be stored on a blockchain. Nonetheless, IPFS does not permit users to share files with selected parties. This is necessary, if sensitive or personal data needs to be shared. Therefore, this paper presents a modified version of the InterPlanetary Filesystem (IPFS) that leverages Ethereum smart contracts to provide access controlled file sharing. The smart contract is used to maintain the access control list, while the modified IPFS software enforces it. For this, it interacts with the smart contract whenever a file is uploaded, downloaded or transferred. Using an experimental setup, the impact of the access controlled IPFS is analyzed and discussed.

Comparing white-box and black-box test prioritization

Abstract: Although white-box regression test prioritization has been well-studied, the more recently introduced black-box prioritization approaches have neither been compared against each other nor against more well-established white-box techniques. We present a comprehensive experimental comparison of several test prioritization techniques, including well-established white-box strategies and more recently introduced black-box approaches. We found that Combinatorial Interaction Testing and diversity-based techniques (Input Model Diversity and Input Test Set Diameter) perform best among the black-box approaches. Perhaps surprisingly, we found little difference between black-box and white-box performance (at most 4% fault detection rate difference). We also found the overlap between black- and white-box faults to be high: the first 10% of the prioritized test suites already agree on at least 60% of the faults found. These are positive findings for practicing regression testers who may not have source code available, thereby making white-box techniques inapplicable. We also found evidence that both black-box and white-box prioritization remain robust over multiple system releases.

Transmission of the Financial and Sovereign Debt Crises to the EMU: Stock Prices, CDS Spreads and Exchange Rates

Abstract: This paper tests for the transmission of the 2007-2010 financial and sovereign debt crises to fifteen EMU countries. We use daily data from 2003 to 2010 on country financial and non-financial stock market indexes. First, we find strong evidence of crisis transmission to European non-financials from US non-financials, whereas the increase in dependence of European financials on US financials is rather limited. Second, in order to test how the sovereign debt crisis affected stock market developments we split the crisis in pre- and post-Lehman sub periods. Results show that financials become significantly more dependent on changes in Greek CDS spreads after Lehman’s collapse, compared to the pre-Lehman sub period. However, this increase is not present for non-financials. Third, before the crisis euro appreciations are associated with European stock market decreases, whereas during the crisis this is reversed. Finally, the reversal in the relationship between the Eurodollar exchange rate and stock prices seems to have been triggered by Lehman’s collapse.