[Spark] Move some ICT test helper utils to InCommitTimestampTestUtils…

….scala (#3843)

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- [X] Spark
- [ ] Standalone
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- [ ] Kernel
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## Description
For code hygiene, we move some ICT test helper utils from the `ICTSuite`
to the object `InCommitTimestampTestUtils`, which is dedicated to
contain the ICT test utils.

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## How was this patch tested?
Existing UTs.
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## Does this PR introduce _any_ user-facing changes?
No.
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spark/src/test/scala/org/apache/spark/sql/delta/InCommitTimestampSuite.scala

@@ -46,30 +46,13 @@ class InCommitTimestampSuite
     with DeltaTestUtilsBase
     with CoordinatedCommitsTestUtils
     with StreamTest {
+  import InCommitTimestampTestUtils._
 
   override def beforeAll(): Unit = {
     super.beforeAll()
     spark.conf.set(DeltaConfigs.IN_COMMIT_TIMESTAMPS_ENABLED.defaultTablePropertyKey, "true")
   }
 
-  private def getInCommitTimestamp(deltaLog: DeltaLog, version: Long): Long = {
-    val deltaFile = DeltaCommitFileProvider(deltaLog.unsafeVolatileSnapshot).deltaFile(version)
-    val commitInfo = DeltaHistoryManager.getCommitInfoOpt(
-      deltaLog.store,
-      deltaFile,
-      deltaLog.newDeltaHadoopConf())
-    commitInfo.get.inCommitTimestamp.get
-  }
-
-  private def getFileModificationTimesMap(
-      deltaLog: DeltaLog, start: Long, end: Long): Map[Long, Long] = {
-    deltaLog.store.listFrom(
-        FileNames.listingPrefix(deltaLog.logPath, start), deltaLog.newDeltaHadoopConf())
-      .collect { case FileNames.DeltaFile(fs, v) => v -> fs.getModificationTime }
-      .takeWhile(_._1 <= end)
-      .toMap
-  }
-
   test("Enable ICT on commit 0") {
     withTempDir { tempDir =>
       spark.range(10).write.format("delta").save(tempDir.getAbsolutePath)

spark/src/test/scala/org/apache/spark/sql/delta/InCommitTimestampTestUtils.scala

@@ -17,7 +17,7 @@
 package org.apache.spark.sql.delta
 
 import org.apache.spark.sql.delta.actions.{Action, CommitInfo}
-import org.apache.spark.sql.delta.util.{FileNames, JsonUtils}
+import org.apache.spark.sql.delta.util.{DeltaCommitFileProvider, FileNames, JsonUtils}
 import org.apache.hadoop.fs.Path
 
 object InCommitTimestampTestUtils {
@@ -55,4 +55,32 @@ object InCommitTimestampTestUtils {
       overwrite = true,
       deltaLog.newDeltaHadoopConf())
   }
+
+  /**
+   * Retrieves the in-commit timestamp for a specific version of the Delta Log.
+   */
+  def getInCommitTimestamp(deltaLog: DeltaLog, version: Long): Long = {
+    val deltaFile = DeltaCommitFileProvider(deltaLog.unsafeVolatileSnapshot).deltaFile(version)
+    val commitInfo = DeltaHistoryManager.getCommitInfoOpt(
+      deltaLog.store,
+      deltaFile,
+      deltaLog.newDeltaHadoopConf())
+    assert(commitInfo.isDefined, s"CommitInfo should exist for version $version")
+    assert(commitInfo.get.inCommitTimestamp.isDefined,
+      s"InCommitTimestamp should exist for CommitInfo's version $version")
+    commitInfo.get.inCommitTimestamp.get
+  }
+
+  /**
+   * Retrieves a map of file modification times for Delta Log versions within a specified version
+   * range.
+   */
+  def getFileModificationTimesMap(
+      deltaLog: DeltaLog, start: Long, end: Long): Map[Long, Long] = {
+    deltaLog.store.listFrom(
+        FileNames.listingPrefix(deltaLog.logPath, start), deltaLog.newDeltaHadoopConf())
+      .collect { case FileNames.DeltaFile(fs, v) => v -> fs.getModificationTime }
+      .takeWhile(_._1 <= end)
+      .toMap
+  }
 }