After creation of Junit test cases, the "Run as Junit Test" disappears

Question

I had made a Junit Test case using menu options in Eclipse. I was getting the option "Run as JUnit Test". But when I was done with my changes, I noticed that the "Run as JUnit Test" disappeared.

On further analysis I found that my initially my TestClass definition was as below :

public class SampleTest
{
....
}

But I had to change the class definition to follows

public class SampleTest<T>   
{
..
}

So what I noticed was adding the generic was creating the behavior. I looked at the following links:

Run As JUnit not appearing in Eclipse - using JUnit4

Missing "Run as JUnit Test"

public class SampleTest<T>
{
..
}

But these links are less related to my issue. So, I need to understand the reason what including Generics has to do with the behavior.

Why do you want to use generic in your test class? When are you going to define its type? — Aditya Narayan Dixit, Jan 04 '19 at 12:09

score 1 · Accepted Answer · edited Jan 04 '19 at 14:13

1

For running a JUnit test class Eclipse needs to

create an instance of your test class by calling its default constructor,
call all the @Test methods on that instance

Here the problem is in step 1: Eclipse doesn't know which type T to use in the constructor.
Should it use new SampleTest<Object>() or new SampleTest<WhatEver>()?
So it decides that it is not a valid JUnit test class and doesn't offer the Run as JUnit Test option.

edited Jan 04 '19 at 14:13

Deep

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answered Jan 04 '19 at 12:13

Thomas Fritsch

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I think it is a valid explanation, because as there is no way to deduce that the class is a valid JUnit test case. – Deep Jan 04 '19 at 12:48

score 0 · Answer 2 · edited Jan 04 '19 at 14:43

0

I may not be able to add much as to why Generics would remove JUnit from starting, but usually test classes act as a wrapper to test a specific class, such as:

public class Sample<T>
{
    ...
}

public class SampleTest
{

    Sample<TypeHere> sample;

    @Before
    public void setUp() throws Exception {
    }
        sample= new Sample<OrTypeHere>(...);
        ...
    }

    @Test
    public void whenConditionOne_verifyExpectedSituation() throws Exception {

        ...
    }
}

edited Jan 04 '19 at 14:43

Deep

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answered Jan 04 '19 at 11:57

DarceVader

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Adding `@RunWith(JUnit4.class)` before your test class is optional when `JUnit3` tests are not present in your test class, this is something I noticed just a little while ago, but may help in forcing tests to be of `JUnit4` – DarceVader Jan 04 '19 at 12:01

After creation of Junit test cases, the "Run as Junit Test" disappears

2 Answers2