Emma coverage on Enum types

Question

I\'m running EclEmma, the Emma plugin for Eclipse, and the coverage report shows only partial coverage for an Enum I\'ve defined, even though it shows the only value in the Enum

Answer 1

I agree with other posters that 100% code coverage can be misguided. But I have to admit to the satisfaction of getting 100% coverage on newly written core code.

Fortunately since all enums extend the same 'class', you can achieve your 100% with a little help from your friend reflection.

Just add the following static method in a class for your testers to call, using [EnumTypeName].class as a parameter.

  public static void superficialEnumCodeCoverage(Class<? extends Enum<?>> enumClass) {
    try {
      for (Object o : (Object[])enumClass.getMethod("values").invoke(null)) {
        enumClass.getMethod("valueOf", String.class).invoke(null, o.toString());
      }
    }
    catch (Throwable e) {
      throw new RuntimeException(e);
    }
  }

Assuming this static function was implemented in a class called "Shared", you would only need to include this line for each enum:

Shared.superficialEnumCodeCoverage(UserRole.class);

The key word is 'superficial'.

Answer 2

What you're seeing is some hidden bytecode being generated due to an enumeration.

To get rid of this issue, add a call to the values() and valueOf() methods in the enum, as mentioned earlier by Carl Manaster and Peter Lawrey.

Answer 3

We ran into a similar issue where the compiler generated methods on enumerations, like values(), typically were not being called in our test code. We worked around the problem by filtering the numbers of our enum objects out of our final report.

This is why I don't like using code coverage as a measure of completeness. When I think of a better metric, I'll let you know. :)