IOTransformDCMTK: Improve tests (migrated from ITKIOTransformDCMTK#5)

[hjmjohnson]

Migrated from InsightSoftwareConsortium/ITK#6358 (originally opened by @jhlegarreta) following the in-tree ingest of IOTransformDCMTK into Modules/IO/IOTransformDCMTK/.

The existing tests under Modules/IO/IOTransformDCMTK/test/ should be improved:

• ITK testing conventions on the naming of the test files should be applied.
• The ITK testing macros should be used consistently (e.g. ITK_TRY_EXPECT_NO_EXCEPTION, ITK_EXERCISE_BASIC_OBJECT_METHODS, etc.) to avoid boilerplate code.
• The tests should run as long as possible and return the status code at the end (use a testStatus and update it as individual checks fail rather than early-returning).
• The coding style should conform to the ITK coding style (Appendix Three).

Current state (post-ingest)

• test/itkDCMTKTransformIOTest.cxx already uses ITK_EXERCISE_BASIC_OBJECT_METHODS, ITK_TRY_EXPECT_NO_EXCEPTION, ITK_TRY_EXPECT_EXCEPTION, ITK_TEST_EXPECT_TRUE, and ITK_TEST_EXPECT_EQUAL, but still return EXIT_FAILURE; on the first nullptr dynamic_cast rather than accumulating a status.
• test/ReadDicomTransformAndResampleExample.cxx is structured as an example-style driver: it uses raw try / catch blocks and per-step return EXIT_FAILURE instead of the ITK testing macros, has no ITK_EXERCISE_BASIC_OBJECT_METHODS coverage, and contains commented-out DCMTKImageIO/DCMTKSeriesFileNames paths (selected over GDCM because "DCMTKImageIO does not populate the MetaDataDictionary yet").

Suggested follow-up scope

1. Convert ReadDicomTransformAndResampleExample.cxx to a proper test driver using ITK testing macros and a testStatus accumulator.
2. Reduce per-test early-returns in itkDCMTKTransformIOTest.cxx to status-accumulating checks where it does not change the test's logical contract.
3. Drop the commented-out DCMTKImageIO/DCMTKSeriesFileNames code blocks, or open a tracking issue for the missing MetaDataDictionary population if that work is still desired.
4. Audit file naming against ITK conventions (itk<Module><Subject>Test.cxx).

Tagging @jhlegarreta as the original reporter.

[hjmjohnson]

First pass landed on branch ingest-IOTransformDCMTK (commit f77c0a9187):

• ✅ itkDCMTKTransformIOTest.cxx converted to the status-accumulating pattern:
  • ITK_TEST_EXPECT_TRUE → ITK_TEST_EXPECT_TRUE_STATUS_VALUE (3 sites)
  • ITK_TEST_EXPECT_EQUAL → ITK_TEST_EXPECT_EQUAL_STATUS_VALUE (2 sites)
  • Added ITK_TEST_SET_GET_VALUE coverage for FrameOfReferenceUID (default + post-Set)
  • Returns testStatus instead of EXIT_SUCCESS
  • auto for SmartPointer locals
• ✅ Already used: ITK_EXERCISE_BASIC_OBJECT_METHODS, ITK_TRY_EXPECT_NO_EXCEPTION, ITK_TRY_EXPECT_EXCEPTION

Remaining work for follow-up PRs:

• ReadDicomTransformAndResampleExample.cxx is structured as an example-style driver with raw try/catch blocks and per-step return EXIT_FAILURE. Either convert to the testing-macro form with a testStatus accumulator, or move it to an Examples directory and replace with a tighter ITK-style test.
• Drop commented-out DCMTKImageIO/DCMTKSeriesFileNames code blocks in the example, or open a separate tracking issue for missing MetaDataDictionary population.
• Audit test file naming against the itk<Module><Subject>Test.cxx convention (ReadDicomTransformAndResampleExample.cxx does not follow the prefix-itk rule).
• Exception macros have no _STATUS_VALUE variants, so ITK_TRY_EXPECT_* calls still early-return; that is acceptable since the rest of the test depends on the reader having succeeded.

[hjmjohnson]

Wave-1 follow-ups landed on branch ingest-IOTransformDCMTK:

• ✅ itkDCMTKTransformIOTest converted to status-accumulating pattern (f77c0a9187).
• ✅ ReadDicomTransformAndResampleExample.cxx refactored to use ITK_TRY_EXPECT_NO_EXCEPTION and ITK_TEST_EXPECT_TRUE_STATUS_VALUE; commented-out DCMTKImageIO/DCMTKSeriesFileNames blocks dropped (7944060ee0).
• ✅ Renamed to itkDCMTKTransformIOResampleTest.cxx + entry-point + ctest name match the ITK itk<TypeUnderTest>Test.cxx convention (94f421a776).
• ✅ Both tests still pass against the existing DicomTransformResampledMovingOutputBaseline.mha baseline.

Remaining (out of this PR's scope; reopen-or-defer):

• Exception macros (ITK_TRY_EXPECT_*) still early-return because no _STATUS_VALUE variants exist upstream; would require a separate ITKTestKernel proposal.
• DCMTKImageIO MetaDataDictionary population gap — separate tracking issue if/when there is demand.

Closing once the parent ingest PR merges.

[jhlegarreta]

Thanks for reviving this and for starting the hard work here @hjmjohnson.