[Rishavbhattarai]

Fixes #18689.

Ports BigQueryIOWriteTest off the deprecated DoFnTester. The only use was in testWritePartition.

Unlike the Datastore and SDF tests, nothing here blocks TestPipeline: WritePartition is serializable and holds no mocks. So the test now runs it through the class's existing p:

• the file list goes in as one Iterable element, the way BatchLoads hands it over, so there's one bundle
• the temp file prefix is a real side input instead of setSideInput
• both outputs get KvCoder.of(ShardedKeyCoder.of(TableDestinationCoder.of()), WritePartition.ResultCoder.INSTANCE), matching BatchLoads
• the existing checks moved into PAssert.satisfies on the expected tag, unchanged except that the empty-table check uses File.length() (no checked exception inside the lambda)

enableAbandonedNodeEnforcement(false) is gone since the pipeline now runs. The two Creates got names to keep transform names stable. The empty singleton file is still deleted after the check, because tearDown asserts the temp dir has no files.

Testing: ./gradlew :sdks:java:io:google-cloud-platform:test --tests 'org.apache.beam.sdk.io.gcp.bigquery.BigQueryIOWriteTest*' passes (220 run, 98 skipped, 0 failures), and spotlessCheck is clean. To make sure the PAssert actually runs, I changed the expected partition count in testWritePartitionLargeFileSize from 4 to 5 and both parameterizations failed.

[github-actions]

📋 Review Summary

This PR cleanly migrates the testWritePartition helper in BigQueryIOWriteTest away from the deprecated DoFnTester to a standard Beam pipeline execution with ParDo and PAssert. The change removes the need to disable abandoned node enforcement and eliminates the remaining DoFnTester usage in the file.

🔍 General Feedback

• The pipeline construction, side input wiring, multi-output tagging, and PAssert verification accurately preserve all original test assertions.
• Consider also asserting that the unselected output tag (singlePartitionTag or multiPartitionsTag) is empty via PAssert.that(...).empty() for slightly stronger coverage, though the current migration is already equivalent to the previous DoFnTester behavior.

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[github-actions]

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