[hjmjohnson]

Adds GoogleTests that exercise ITK's exception classes directly, so a test of a filter that throws only needs to check the throw, not print the exception for coverage. Run alone, the exception tests cover 100% of the exception-class lines (196 of 196), up from 71% today.

What is covered

File	Classes
Core/Common/test/itkCommonExceptionsGTest.cxx	MemoryAllocationError, RangeError, InvalidArgumentError, IncompatibleOperandsError, DerefError, ProcessAborted, DataObjectError, InvalidRequestedRegionError
IO/ImageBase/test/itkImageIOExceptionsGTest.cxx	ImageFileReaderException, ImageFileWriterException, ImageSeriesWriterException
IO/MeshBase/test/itkMeshIOExceptionsGTest.cxx	MeshFileReaderException, MeshFileWriterException
Numerics/Statistics/test/itkSampleToHistogramFilterExceptionsGTest.cxx	the seven itkDeclareExceptionMacro exceptions in itkSampleToHistogramFilter.h

Each class is checked for its name, construction (default and with file, line, description, and location), Print output, copy and move, and use through a base-class reference. Throwability is checked at compile time (static_assert on the base class and on non-throwing copy), not by throwing in the test. DataObjectError and InvalidRequestedRegionError are printed both without a data object ("(None)") and with an image attached, which also checks that the image's PrintSelf output appears. IOMeshBase gets its first GoogleTest driver.

Why

Most exception-class code was covered as a side effect of filter tests printing the exceptions they caught. DataObjectError::Print, for example, was reached only through the ImageCompare, ImageCompose, and ImageGrid test drivers. Tests dedicated to the exceptions keep that coverage when filter tests use plain EXPECT_THROW.

Verification

• LLVM source-based coverage build (macOS, Apple clang) of ITKCommon, ITKIOImageBase, ITKIOMeshBase, and ITKStatistics; only ExceptionObject.*, the four new suites, and itkExceptionObjectTest run:

  	Exception-class lines covered
  main	137 / 192 (71.4%)
  this PR	196 / 196 (100%)

• All GoogleTests in the four drivers pass under CTest, and the build has no warnings.

• pre-commit run --all-files passes.

AI assistance

An AI coding assistant wrote the tests and ran the coverage measurement under the author's direction.

[greptile-apps]

Confidence Score: 5/5

[Low impact] This test-only change appears safe to merge.

Summary

Adds 20 focused GoogleTests for exception classes across four modules.

• Common exceptions now have direct tests for their reported details.
• Image IO exceptions now have direct tests for their messages and locations.
• Mesh IO exceptions now have direct tests in a GoogleTest driver.
• Histogram exceptions now have direct tests for their names and messages.

No actionable issues found. Tests were not run during this review.

_{Reviews (1) · Last reviewed commit: "ENH: Add GoogleTests covering ITK except..." · Reviewed by Greptile}

[dzenanz]

Niels has reviewed this PR. Philosophically, I am in favor. I prefer to skip reviewing it in detail.

[N-Dekker]

Niels has reviewed this PR.

Sorry, @dzenanz, I did not review all 500+ added lines of code so far. I just did some cherry-picking on low hanging fruit. Although I do agree philosophically 😸

[hjmjohnson]

Two force-pushes: f62b3ff → b05d135 is a plain rebase on main; b05d135 → 0418064 holds only the review fixes.

[hjmjohnson]

One more content-only push, 0418064 → 7e99108: the seven EXPECT_TRUE(a == b) checks are now EXPECT_EQ(a, b), so a failure prints both exceptions.

[N-Dekker]

As a future improvement, I think it would be nice if we could use GoogleTest Matchers like HasSubstr, instead of using our own local Contains helper function:

EXPECT_THAT(printedWithoutDataObject, HasSubstr("itk::" + expectedName));

But for now, EXPECT_TRUE(Contains(... is fine to me. 👍

[hjmjohnson]

Agreed that matchers would be nicer. They need googlemock, though, and ITK neither vendors it nor builds it: UpdateFromUpstream.sh imports only googletest/, BUILD_GMOCK is forced OFF, and the drivers link only GTest::gtest. So I am keeping Contains here and treating matchers as out of scope until a larger investigation of using gMock in ITK is done: its benefit to the tests, the cost of vendoring it, and the system-GoogleTest builds. I will bring that to Discourse before proposing a change.

[N-Dekker]

Thanks Hans! Approved 👍

[hjmjohnson]

Content-only push after your approval, 7e99108 → 324ca0c: TParent is renamed to TExpectedBaseClass, and single-call TESTs are merged into one TEST per helper. No checks changed.