@Test
  public void testIsFileExists_FileAbsent() {
    // Arrange
    final BootstrapController bootstrapController =
        new BootstrapController(storeManager, storeConfig, serverConfig, primaryClusterParticipant);

    PartitionId partitionId = mock(PartitionId.class);
    String fileName = "test_file";

    // Act
    // Mock file absence
    when(storeManager.isFileExists(partitionId, fileName)).thenReturn(false);

    // Assert
    // Verify the method returns false
    assertFalse(bootstrapController.new BootstrapControllerImpl().isFileExists(partitionId, fileName));
  }
Test for {@link BootstrapController.BootstrapControllerImpl#onPartitionBecomeBootstrapFromOffline(String)}
when :-
1. The server replication mode is {@link ServerReplicationMode#FILE_BASED}
2. Replica is not null
3. Bootstrap_in_progress file doesn't exist
4. Filecopy_in_progress file doesn't exist
5. Atleast one LogSegment File exists for the partition
Bootstrap Controller is expected to instantiate storageManagerListener
ReplicationProtocolTransitionType is either of the following types :-
a. {@link ReplicationProtocolTransitionType#BLOB_BASED_HYDRATION_COMPLETE_TO_FILE_BASED_HYDRATION} state
b. {@link ReplicationProtocolTransitionType#FILE_BASED_HYDRATION_COMPLETE_TO_FILE_BASED_HYDRATION} state
ambry-store/src/test/java/com/github/ambry/store/BootstrapControllerTest.java