CS 580 Client-Server Programming Fall Semester, 2000 Testing Hidden Methods
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Testing and Hidden Methods/State
How to Test Hidden Methods Directly?

Method 1: Relax the protection level
Method 2: Use inner classes
Method 3: Use reflection

Doc 11, Testing Hidden Methods Slide # 2

1. Send the craft in the general direction of the target
2. As you get closer to the target, adjust the craft's direction
3. Repeat 2 until you reach the target

Doc 11, Testing Hidden Methods Slide # 3

Testing and Hidden Methods/State

• How does one test hidden methods?

• Direct access to an object's state can reduce the time needed to write a test

Doc 11, Testing Hidden Methods Slide # 4

• Can not test everything
• Clients of an object only care if public interface works correctly
• Testing public interface also tests hidden methods
• Hidden methods are more likely to change, requiring changes to the tests

• The closer the test is to the code it tests the easier the test
• Bugs in hidden methods can make it hard to debug public methods

Doc 11, Testing Hidden Methods Slide # 5

How to Test Hidden Methods Directly?

Method 1: Relax the protection level

• Make the method package level access
• Place the test class in the same package as the tested code

• Makes it possible to test the hidden method
• Clients outside the package can not access the method

• Clients in the package may then use the method
• Requires organizational discipline to avoid using the method

Doc 11, Testing Hidden Methods Slide # 6

Method 2: Use inner classes

import junit.framework.TestCase;
public class Foo {
    private int value;
    private void bar() {
        value = 10;
    }
    public static class FooTest extends TestCase {
        public FooTest(String name) {
            super(name );
        }
        public void testBar() {
            Foo a = new Foo();
            a.bar();
            assert( 10 == a.value );
        }
    }
}

• Provides access to all methods/fields
• Test does not have to be shipped with production code
• Test stays with tested class

• Source files are bit harder to read
• Must remove all inner $class files from production code
• Test not with other test classes

Doc 11, Testing Hidden Methods Slide # 7

Method 3: Use reflection

• Java reflection provides access to all methods/fields of a class
• Does not require any changes to tested class

• Reflection can be slow
• Reflection is cumbersome to use
• Requires setting permission files

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