Refactor

[macalbert]

Summary

Added CI workflow that checks out the code, sets up JDK 11, and runs Maven tests

Updated the generateParquetFileFor method to return the generated Path for testing

[gemini-code-assist]

Hello @macalbert, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

Summary of Changes

Hello team, gemini-code-assist here to provide a summary of this pull request. The primary goal of this PR, as indicated by the title and description, is to refactor the existing code structure to make it more testable and to introduce automated testing using the Arrange-Act-Assert (AAA) pattern. This involves setting up the necessary build infrastructure for running tests and modifying the application code to facilitate testing, specifically by making the generateParquetFileFor method return the path of the generated file.

Highlights

• Testing Infrastructure Setup: Adds the Maven Surefire plugin and JUnit 4 dependency to the pom.xml to enable running unit tests as part of the build process.
• Method Refactoring for Testability: The generateParquetFileFor method in App.java has been modified to be public static and now returns the Path object representing the generated Parquet file. This allows tests to easily access and verify the output of this method.
• New Unit Test with AAA Pattern: Introduces a new JUnit test class AppTest.java that includes a test case (Should_CreateParquetFile_When_CallingGenerateParquetFileFor) following the Arrange-Act-Assert pattern. This test verifies that calling generateParquetFileFor successfully creates a file and checks its basic structure (the 'PAR1' magic bytes).
• Exception Handling in Main: Added a try-catch block around the calls to generateParquetFileFor in the main method of App.java to handle potential exceptions gracefully during execution.

Changelog

Click here to see the changelog

• pom.xml
  • Added maven-surefire-plugin version 2.22.2 to the build plugins.
  • Added JUnit dependency version 4.13.2 with test scope.
• src/main/java/com/instarsocial/parquet/App.java
  • Wrapped calls to generateParquetFileFor in main with a try-catch block (lines 26-30).
  • Changed the visibility of generateParquetFileFor from private to public (line 34).
  • Changed the return type of generateParquetFileFor from void to Path (line 34).
  • Added return path; at the end of generateParquetFileFor (line 56).
• src/test/java/com/instarsocial/parquet/AppTest.java
  • Added new test class AppTest.
  • Added @BeforeClass method beforeAll for setup (lines 23-26).
  • Added @AfterClass method afterAll for cleanup (lines 28-32).
  • Added test method Should_CreateParquetFile_When_CallingGenerateParquetFileFor using JUnit's @Test annotation (lines 35-54).
  • Implemented Arrange, Act, and Assert steps within the test method to verify file creation and magic bytes.

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---

Tests arranged with care,
Act, then assert, check the file there,
Parquet bytes align,
Code quality shines,
Refactored, now tests are everywhere.

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[gemini-code-assist]

Code Review

This pull request introduces a Maven Surefire plugin for running tests, adds JUnit as a test dependency, and refactors the generateParquetFileFor method to return the generated Path object, which significantly improves its testability. A new test class AppTest has been added to verify the Parquet file generation.

The changes are generally positive and move towards better code quality and test coverage. I've identified a couple of areas for improvement, primarily related to exception handling and logging practices. I'm defaulting to the Google Java Style Guide for general Java best practices as no specific style guide was provided.

Summary of Findings

• Exception Handling in main: The main method uses e.printStackTrace(System.out) to handle exceptions from generateParquetFileFor. It's recommended to use a proper logging framework or at least print to System.err.
• Generic Exception Declaration: The generateParquetFileFor method declares throws Exception, which is too broad. It should declare more specific exceptions like java.io.IOException.
• Maven Surefire Plugin Version (Low Severity - Not Commented): The maven-surefire-plugin is added with version 2.22.2. While functional, newer versions (3.x series) are available and might offer improvements. This was not commented on due to review settings.
• JUnit Version (Low Severity - Not Commented): JUnit 4 (4.13.2) is used for tests. For new projects or major refactors, JUnit 5 (Jupiter) is generally preferred. This was not commented on due to review settings.
• Test Method Naming Convention (Low Severity - Not Commented): The test method Should_CreateParquetFile_When_CallingGenerateParquetFileFor uses underscores, which is less common in Java than camelCase (e.g., shouldCreateParquetFileWhenCallingGenerateParquetFileFor). This is a stylistic point and was not commented on due to review settings.
• Test File Cleanup (Low Severity - Not Commented): In AppTest.afterAll(), generatedFile.delete() might fail silently. For robustness in test environments, logging a warning on failure could be considered. This was not commented on due to review settings.

Merge Readiness

The pull request makes good progress in improving testability. However, there are a couple of medium-severity issues related to exception handling that should be addressed before merging. Specifically, the use of e.printStackTrace() and the generic throws Exception declaration could be improved for better maintainability and error diagnostics. Once these points are addressed, the PR should be in good shape. As a reviewer, I am not authorized to approve the pull request; please ensure it undergoes further review and approval as per your team's process.

[gemini-code-assist]

Using e.printStackTrace() is generally discouraged in application code, especially when writing to System.out. It can be difficult to manage and control log output this way.

Could we consider using a dedicated logging framework (like SLF4J with Logback or Log4j2) here? This would provide more robust and configurable logging.

For example, with SLF4J:

// At class level:
// private static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(App.class);

// In catch block:
logger.error("Failed to generate Parquet file for date: {}", dateTime.plusDays(i), e);

If adding a full logging framework is out of scope for this PR, at least consider writing to System.err for errors, or re-throwing a custom exception if main shouldn't handle this directly.

                // Consider using a proper logger here, e.g., logger.error("Error generating Parquet file", e);
                e.printStackTrace(System.err); // At a minimum, print to System.err for errors

[gemini-code-assist]

Declaring throws Exception is quite broad and can make it harder for callers to understand and handle specific error conditions. It's generally better to declare more specific exceptions that the method might throw (e.g., java.io.IOException, or a custom application-specific exception).

Looking at the Parquet writer and file operations, java.io.IOException seems like a primary candidate. Would it be more appropriate to declare throws IOException or a more specific custom exception here?

public static Path generateParquetFileFor(DateTime dateTime) throws java.io.IOException {