Add junit compilation test integration

[XDean]

Add support to quick build compile-period or compilation test in JUnit.

1. Compile period test. Use @Compile on your test method.

@Test
@Compile(sources = "/HelloWorld.java")
public void test(RoundEnvironment env) {
  // Now you are in compile (Annotation Processor) context which is compiling your sources.
}

2. Compilation test. Use @Compiled on your test method.

@Test
@Compiled(sources = "/HelloWorld.java")
public void test(Compilation c) {
  // Now your sources have been compiled.
  // Do assert on the Compilation.
}

• CI passed
• Test coverage for new files: 100%
• Use Samples: Sample 1, Sample 2

[ronshapiro]

This surely is interesting, but I don't see the value of using an annotation vs. defining this code in a java method.

It seems like the main benefit is that you can specify the files directly via strings and omit the JavaFileObjects.fromResource() invocation. Not sure how valuable that is (maybe you can define a utility function?)

The downsides that initially come to my mind are:

• you can't specify different compilers
• you can't use JavaFileObjects.forSourceLines()
• because there's no reference to a JavaFileObject, you can't refer to a particular line when you want to reference an diagnostic
• if we implement a JUnit runner, we're stuck not being able to use other runners like Parameterized without totally changing the way the tests are written.

[XDean]

@ronshapiro Yes, you are right. @Compiled is just an abridge of Compile...JavaFileObjects....
But @Compile really has its value.

This project name is 'compile-testing', but it is only care about the compile result not the compile itself. For example

1. Someone is developing some utilities for AnnotationProcessor, how can it be tested?
2. Someone is developing an annotation processor. But he want to do a unit test for some methods. how can he test it?

Use @Compile can quick build a compile-period test, which is (I think) also 'Compile-Testing'.

[XDean]

@ronshapiro And for your 4 points

you can't specify different compilers.

I can add support if anyone want.

you can't use JavaFileObjects.forSourceLines()

Although I can add support, I think is a bad usage. You should extract source code into new file instead of embed in your test code. But if you really need it, I can support it.

because there's no reference to a JavaFileObject, you can't refer to a particular line when you want to reference an diagnostic

I can't understand your use case. You can get JavaFileObject from the Diagnostic and its name by getName. If you really want the reference, it's ok to use simple @Test junit test method in CompileTestCase.

if we implement a JUnit runner, we're stuck not being able to use other runners like Parameterized without totally changing the way the tests are written.

Yes, it is. But it's not a problem as you can't use MockitoRunner with Parameterized together. No framework can cover all complex requirement.

[stauvel]

No activity since 2 years here... Is there anyone to accept this PR ?