1. Create ITestBean interface.
2. Create public class TestBeanImpl implements ITestBean

{...}
3. Add @Inject ITestBean foo; field to any bean but TestBeanImpl.
4. Validate the project. @Inject ITestBean foo; is valid since there is the only bean TestBeanImpl to be injected.
5. Create public class TestBeanImpl2 implements ITestBean {...}

. Save the file, build the project (using the incremental builder).
6. @Inject ITestBean foo; is not valid anymore because there are two beans TestBeanImpl and TestBeanImpl2 to be injected. But CDI validator doesn't re-validate @Inject ITestBean foo; We have to change/validate the file with the injection to re-validate it and have a marker on this invalid injection.

Slava, let's add
IInjectionPoint getInjections(String fullyQuilifeidTypeName);
method to IBeanManager interface and its implementation. Then assign the issue to me and I will fix this bug in CDI validator.