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Graph neural networks (GNNs) have limited expressive power, failing to represent many graph classes correctly. While more expressive graph representation learning (GRL) alternatives can distinguish some of these classes, they are significantly harder to implement, may not scale well, and have not been shown to outperform well-tuned GNNs in real-world tasks. Thus, devising simple, scalable, and expressive GRL architectures that also achieve real-world improvements remains an open challenge. In this work, we show the extent to which graph reconstruction---reconstructing a graph from its subgraphs---can mitigate the theoretical and practical problems currently faced by GRL architectures. First, we leverage graph reconstruction to build two new classes of expressive graph representations. Secondly, we show how graph reconstruction boosts the expressive power of any GNN architecture while being a (provably) powerful inductive bias for invariances to vertex removals. Empirically, we show how reconstruction can boost GNN's expressive power---while maintaining its invariance to permutations of the vertices---by solving seven graph property tasks not solvable by the original GNN. Further, we demonstrate how it boosts state-of-the-art GNN's performance across nine real-world benchmark datasets. 

When developers make changes to their code, they typically run regression tests to detect if their recent changes (re)introduce any bugs. However, many tests are flaky, and their outcomes can change non-deterministically, failing without apparent cause. Flaky tests are a significant nuisance in the development process, since they make it more difficult for developers to trust the outcome of their tests. The traditional approach to identify flaky tests is to rerun them multiple times: if a test is observed both passing and failing on the same code, it is definitely flaky. We conducted a very large empirical study looking for flaky tests by rerunning the test suites of 24 projects 10,000 times each, and found that even with this many reruns, some flaky tests were still not detected. We propose FlakeFlagger, a novel approach that collects a set of features describing the behavior of each test, and then predicts tests that are likely to be flaky based on similar behavioral features. We found that FlakeFlagger correctly labeled at least as many tests as flaky as a state-of-the-art flaky test classifier, but that FlakeFlagger reported far fewer false positives (an increase in precision from just 11% to 60%). This lower false positive rate translates directly to saved time for researchers and developers who use the classification result to guide more expensive flaky test detection processes. By investigating the information gain of each feature, we conclude that test execution time, overall test coverage, coverage of recently changed lines and usage of third party libraries are effective predictors of test flakiness. We did not find any keywords or tokens in the source code of tests that were effective in predicting test flakiness, and did not find the presence of test smells to be effective in predicting test flakiness. This archive contains the dataset that we collected of flaky tests, along with the features that we collected from each test. Contents: Project_Info.csv: List of projects and their revisions studied build-logs-<project-slug>.tgz: An archive of all of the maven build logs from each of the 10,000 runs of that project's test suite.  failing-test-reports-<project-slug>.tgz An archive of all of the surefire XML reports for each failing test of each build of each project. test_results.csv: Summary of the number of passing and failing runs for each test in each project.  "Run ID" is a key into the <project-slug>.tgz archive also in this artifact, which refers to the run that we observed the test fail on. test_features.csv: Summary of the features that each test had, as per our feature detectors described in the paper flakeflagger-code.zip: All scripts used to generate and process these results. These scripts are also located at https://github.com/AlshammariA/FlakeFlagger