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Burst constructor with value class parameter fails #93

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swankjesse opened this issue Jan 25, 2025 · 1 comment · Fixed by #94
Closed

Burst constructor with value class parameter fails #93

swankjesse opened this issue Jan 25, 2025 · 1 comment · Fixed by #94

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@swankjesse
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swankjesse commented Jan 25, 2025 •
edited
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Here’s a test class that accepts a value class as a parameter:

@Burst
class CoffeeTest(
  private val espresso: Espresso = burstValues(...),
) {
  @Test
  fun test() {
    println("running $espresso")
  }
}

@JvmInline
value class Espresso private constructor(private val ordinal: Int) { ... }

It fails like this:

CoffeeTest[jvm] > initializationError[jvm] FAILED
    java.lang.IllegalArgumentException: Test class can only have one constructor
        at org.junit.runners.model.TestClass.<init>(TestClass.java:48)
        at org.junit.runners.JUnit4.<init>(JUnit4.java:23)
        at org.junit.internal.builders.JUnit4Builder.runnerForClass(JUnit4Builder.java:10)
        at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:70)
        at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:37)
        at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:70)

As a side-effect of some value class implementation details, the compiler generates an extra constructor overload. Unfortunately that overload is generated after Burst does its edits.

The JUnit API expects a single public constructor.

I can’t think of an easy way to make this work.
@swankjesse
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Okay, I think there’s a simple enough fix...

If any constructor parameter is a value class, we treat it as if there’s no default specialization. That’ll send us into a code path that marks the class as abstract and causes JUnit to ignore both constructors.

      // There's no default specialization. Make the class abstract so JUnit skips it.
      original.modality = Modality.ABSTRACT

swankjesse pushed a commit that referenced this issue Jan 25, 2025
@squarejesse
Don't generate a broken test when a constructor has a value class par…
d301463 
…ameter

An implementation detail of the Kotlin compiler gets in our way.

Closes: #93
@swankjesse swankjesse mentioned this issue Jan 25, 2025
Merged
swankjesse added a commit that referenced this issue Jan 27, 2025
@swankjesse @squarejesse
Don't generate a broken test when a constructor has a value class par…
c9f361f 
…ameter (#94)

An implementation detail of the Kotlin compiler gets in our way.

Closes: #93

Co-authored-by: Jesse Wilson <[email protected]>
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Don't generate a broken test when a constructor has a value class parameter cashapp/burst
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@swankjesse