In unit testing, mocking is popularly used to ease test effort, reduce test flakiness, and increase test coverage by replacing the actual dependencies with simple implementations. However, there are no clear criteria to determine which dependencies in a unit test should be mocked. Inappropriate mocking can have undesirable consequences: under-mocking could result in the inability to isolate the class under test (CUT) from its dependencies while over-mocking increases the developers’ burden on maintaining the mocked objects and may lead to spurious test failures. According to existing work, various factors can determine whether a dependency should be mocked. As a result, mocking decisions are often difficult to make in practice. Studies on the evolution of mocked objects also showed that developers tend to change their mocking decisions: 17% of the studied mocked objects were introduced sometime after the test scripts were created and another 13% of the originally mocked objects eventually became unmocked. In this work, we are motivated to develop an automated technique to make mocking recommendations to facilitate unit testing. We studied 10,846 test scripts in four actively maintained open-source projects that use mocked objects, aiming to characterize the dependencies that are mocked in unit testing. Based on our observations on mocking practices, we designed and implemented a tool, MockSniffer, to identify and recommend mocks for unit tests. The tool is fully automated and requires only the CUT and its dependencies as input. It leverages machine learning techniques to make mocking recommendations by holistically considering multiple factors that can affect developers’ mocking decisions. Our evaluation of Mock- Sniffer on ten open-source projects showed that it outperformed three baseline approaches, and achieved good performance in two potential application scenarios.

Hengcheng Zhu

Southern University of Science and Technology

China

Lili Wei

The Hong Kong University of Science and Technology

Ming Wen

Huazhong University of Science and Technology, China

China

Yepang Liu

Southern University of Science and Technology

Shing-Chi Cheung

Hong Kong University of Science and Technology, China

China

Qin Sheng

WeBank Co Ltd

Cui Zhou

WeBank Co Ltd

Today, most automated test generators, such as search-based software testing (SBST) techniques focus on achieving high code coverage. However, high code coverage is not sufficient to maximise the number of bugs found, especially when given a limited testing budget. In this paper, we propose an automated test generation technique that is also guided by the estimated degree of defectiveness of the source code. Parts of the code that are likely to be more defective receive more testing budget than the less defective parts. To measure the degree of defectiveness, we leverage Schwa, a notable defect prediction technique.

We implement our approach into EvoSuite, a state of the art SBST tool for Java. Our experiments on the Defects4J benchmark demonstrate the improved efficiency of defect prediction guided test generation and confirm our hypothesis that spending more time budget on likely defective parts increases the number of bugs found in the same time budget.

Anjana Perera

Monash University

Australia

Aldeida Aleti

Monash University

Australia

Marcel Böhme

Monash University, Australia

Australia

Burak Turhan

Monash University

Australia

Crowdsourced mobile testing has been widely used due to its convenience and high efficiency. Crowdsourced workers complete testing tasks and record results in test reports. However, the problem of duplicate reports has prevented the efficiency of crowdsourced mobile testing from further improving. Existing crowdsourced testing report analysis techniques usually leverage screenshots and text descriptions independently, but fail to recognize the link between these two types of information. In this paper, we present a crowdsourced mobile testing report selection tool, namely STIFA, to extract image and text feature information in reports and establish an image-text-fusion bug context. Based on text and image fusion analysis results, STIFA performs cluster analysis and report selection. To evaluate, we employed STIFA to analyze 150 reports from 2 apps. The results show that STIFA can extract, on average, 95.23% text feature information and 84.15% image feature information. Besides, STIFA reaches an accuracy of 87.64% in detecting duplicate reports. The demo can be found at https://github.com/ZhenfeiCao/STIFA.

Zhenfei Cao

Nanjing University

Xu Wang

Nanjing University

Shengcheng Yu

Nanjing University, China

China

Yexiao Yun

Nanjing University

Chunrong Fang

Nanjing University, China

China