samples(testing): add retry rule

[anguillanneuf]

Fixes #552

I referenced: https://www.lenar.io/how-to-re-run-failed-tests-junit/

Alternatively, upgrade to junit5 and use @RepeatedTest annotation: https://www.swtestacademy.com/junit-5-how-to-repeat-failed-test/ ← Not super useful because it retries successful runs.

Also tried

    <dependency>
      <groupId>com.google.cloud</groupId>
      <artifactId>google-cloud-core</artifactId>
      <version>1.94.3</version>
    </dependency>

But unable to import com.google.cloud.testing.junit4.MultipleAttemptsRule;

Turned out that I need <classifier>tests</classifier> tag.

[codecov]

Codecov Report

Merging #565 (fb6c36e) into master (0dd6d2d) will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master     #565   +/-   ##
=========================================
  Coverage     78.73%   78.73%           
  Complexity      378      378           
=========================================
  Files            27       27           
  Lines          3418     3418           
  Branches        171      171           
=========================================
  Hits           2691     2691           
  Misses          653      653           
  Partials         74       74           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0dd6d2d...fb6c36e. Read the comment docs.

[kolea2]

@BenWhitehead could we use the junit rules you wrote here?

[anguillanneuf]

junit5 has a @RepeatedTest annotation if we can upgrade?

[kolea2]

Sorry, let me clarify here :) @BenWhitehead worked on some shared JUnit rules in java-core, wondering if we can make use of them - https://github.com/googleapis/java-core/pull/327/files. @anguillanneuf let me know if these are a good fit for what you're trying to accomplish, otherwise feel free to ignore my suggestion :)

[anguillanneuf]

https://github.com/googleapis/java-core/blob/master/google-cloud-core/src/test/java/com/google/cloud/testing/junit4/MultipleAttemptsRule.java is what I need, but it's in src/test/, is that something I can import?

Do you know if we can use this for testing?

 <dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>5.7.1</version>
    <scope>test</scope>
</dependency>

[anguillanneuf]

FWIW, I tried junit5, but the RepeatedTest annotation naively retries even if test succeeds. I reverted my changes.

[lesv]

We aren't using Junit 5 yet, I don't remember the reason why, ask at Java Samples Office Hours. (I think it's reasonable to upgrade, but it's also a huge effort - perhaps we can just do it one at a time)

[generated-files-bot]

Warning: This pull request is touching the following templated files:

• samples/install-without-bom/pom.xml
• samples/snapshot/pom.xml
• samples/snippets/pom.xml