Kotlin Compile Testing

A library for in-process compilation of Kotlin and Java code, in the spirit of Google Compile Testing. For example, you can use this library to test your annotation processor or compiler plugin.

Use Cases

• Compile Kotlin and Java code in tests
• Test annotation processors
• Test compiler plugins
• Test Kotlin code generation

Example

Create sources

class TestEnvClass {}

@Test
fun `test my annotation processor`() {
    val kotlinSource = SourceFile.kotlin("KClass.kt", """
        class KClass {
            fun foo() {
                // Classes from the test environment are visible to the compiled sources
                val testEnvClass = TestEnvClass() 
            }
        }
    """)   
      
    val javaSource = SourceFile.java("JClass.java", """
        public class JClass {
            public void bar() {
                // compiled Kotlin classes are visible to Java sources
                KClass kClass = new KClass(); 
            }
    """)

Configure compilation

    val result = KotlinCompilation().apply {
        sources = listOf(kotlinSource, javaSource)
        
        // pass your own instance of an annotation processor
        annotationProcessors = listOf(MyAnnotationProcessor()) 

        // pass your own instance of a compiler plugin
        compilerPlugins = listOf(MyComponentRegistrar())
        
        inheritClassPath = true
        messageOutputStream = System.out // see diagnostics in real time
    }.compile()

Assert results

    assertThat(result.exitCode).isEqualTo(ExitCode.OK)	
    
    // Test diagnostic output of compiler
    assertThat(result.messages).contains("My annotation processor was called") 
    
    // Load compiled classes and inspect generated code through reflection
    val kClazz = result.classLoader.loadClass("KClass")
    assertThat(kClazz).hasDeclaredMethods("foo")
}

Features

• Mixed-source sets: Compile Kotlin and Java source files in a single run
• Annotation processing:
  • Run annotation processors on Kotlin and Java sources
  • Generate Kotlin and Java sources
  • Both Kotlin and Java sources have access to the generated sources
  • Provide your own instances of annotation processors directly to the compiler instead of letting the compiler create them with a service locator
  • Debug annotation processors: Since the compilation runs in the same process as your application, you can easily debug it instead of having to attach your IDE's debugger manually to the compilation process
• Inherit classpath: Compiled sources have access to classes in your application
• Project Jigsaw compatible: Kotlin-Compile-Testing works with JDK 8 as well as JDK 9 and later
• JDK-crosscompilation: Provide your own JDK to compile the code against, instead of using the host application's JDK. This allows you to easily test your code on all JDK versions
• Find dependencies automatically on the host classpath

Installation

The package is available on mavenCentral and jitpack.

Add dependency to your module's build.gradle file:

dependencies {
        // ...
	implementation 'com.github.tschuchortdev:kotlin-compile-testing:1.2.4'
}

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License

Copyright (C) 2019 Thilo Schuchort

Licensed under the Mozilla Public License 2.0

For custom license agreements contact me directly