Coverage for private constructor junit/emma [duplicate]

Question

This question already has answers here:

How to add test coverage to a private constructor? (18 answers)

Closed 4 years ago.

how can i write a @test class for a private constructor. i want to cover it with emma tool too.

public final class Product {

    private Product() {

    }
}

can someone suggest a simple way?

thanks.

Answer 1

The best way to test private methods is to use Reflection.

There are many ways, but I would simple do this;

@Test
    public void testConstructorIsPrivate() throws Exception {
      Constructor constructor = Product.class.getDeclaredConstructor();
      assertTrue(Modifier.isPrivate(constructor.getModifiers()));
      constructor.setAccessible(true);
      constructor.newInstance();
    }

This will cover the constructor when running the coverage tool emma.

Answer 2

I don't think you should test private constructors, since they are part of the implementation. Write tests only for API methods with well-defined contracts.