Description

This PR restores single class tests for MatthewsCorrelationCoefficient. These tests have been removed in #2406 which unfortunately broke MatthewsCorrelationCoefficient with num_classes=1. This was a breaking change which doesn't seem like it was intended. These test will currently fail on master but passed in 0.12.1 (or any version before #2406).

Please consider this PR as an issue report. ~~Unfortunately I don't have time time right now to properly look into fixing this issue, but maybe @jonpsy knows more about this.~~ fixed in #2495

/cc @jonpsy @bhack @seanpmorgan

Type of change

• [ ] Bug fix
• [ ] New Tutorial
• [ ] Updated or additional documentation
• [x] Additional Testing
• [ ] New Activation and the changes conform to the activation contribution guidelines
• [ ] New Callback and the changes conform to the callback contribution guidelines
• [ ] New Image addition and the changes conform to the image op contribution guidelines
• [ ] New Layer and the changes conform to the layer contribution guidelines
• [ ] New Loss and the changes conform to the loss contribution guidelines
• [ ] New Metric and the changes conform to the metric contribution guidelines
• [ ] New Optimizer and the changes conform to the optimizer contribution guidelines
• [ ] New RNN Cell and the changes conform to the rnn contribution guidelines
• [ ] New Seq2seq addition and the changes conform to the seq2seq contribution guidelines
• [ ] New Text addition and the changes conform to the text op contribution guidelines

Checklist:

• [x] I've properly formatted my code according to the guidelines
  • [x] By running Black + Flake8
  • [x] By running pre-commit hooks
• [ ] This PR addresses an already submitted issue for TensorFlow Addons
• [ ] I have made corresponding changes to the documentation
• [x] I have added tests that prove my fix is effective or that my feature works
• [ ] This PR contains modifications to C++ custom-ops