Regression Test

[ghost]

This pull request adds a simple regression test borrowing heavily from @jrood-nrel's Nalu regression test and @gantech's fastCPPtests.

The test configuration is handled with CTest, so the test is only built if the appropriate CMake flag, ENABLE_TESTS, is ON.

The regression test itself is driven by reg_tests/executeRegressionTestCase.py which runs the OpenFAST test case and compares the binary output to the "gold standard" with reg_tests/pass_fail.py. The pass/fail criteria is a comparison of the variance of each channel in the binary output file with a predetermined tolerance. The tolerance is automatically picked by CMake based on machine and compiler type.

The test data is included in a submodule called RegressionTestData which based on the CertTest directory in FAST v8. This repository has two subdirectories: inputs and outputs. The contents of inputs are used in CTest configuration and the contents of outputs are the "gold standard" solutions. There is also a python script runCertTestsLocally.py which executes all of the cases in inputs in a new directory outputs-local.

To run the test from a fresh clone:
git clone https://github.com/rafaelmudafort/openfast.git
cd openfast
git checkout dev
git submodule update --init --recursive
mkdir build
cd build
ccmake .. # or otherwise configure cmake flags
-- hit c, then e
-- turn on the test boolean, configure the install prefix, etc
-- hit c, then e
-- again hit c, then e
-- hit g
make
make test

Improvements to come:

• determine appropriate machine/compiler specific tolerances
• add support in ctest for selecting a target reference directory
  • this would allow a developer to generate their own "gold standards" in case of new feature implementation or improvement
• cron job & CDash