The test classes are to be written for triggers and classes, and then run those test classes to generate code coverage information.

The file types includes are triggers(.trigger) and classes (.cls) from metadata.

Reference link Testing and Code Coverage

The test classes are to be written for triggers and classes, and then run those test classes to generate code coverage information.

The file types includes are triggers(.trigger) and classes (.cls) from metadata. Test coverage is not needed for visual force pages.

Reference link Testing and Code Coverage