Add flag to turn power assertions on/off (#1419)

pkl-core/src/test/kotlin/org/pkl/core/EvaluateTestsTest.kt

@@ -28,7 +28,7 @@ import org.pkl.core.ModuleSource.*
 
 class EvaluateTestsTest {
 
-  private val evaluator = Evaluator.preconfigured()
+  private val evaluator = EvaluatorBuilder.preconfigured().setPowerAssertionsEnabled(true).build()
 
   @Test
   fun `test successful module`() {

pkl-core/src/test/kotlin/org/pkl/core/LanguageSnippetTestsEngine.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright © 2024-2025 Apple Inc. and the Pkl project authors. All rights reserved.
+ * Copyright © 2024-2026 Apple Inc. and the Pkl project authors. All rights reserved.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -178,6 +178,7 @@ class LanguageSnippetTestsEngine : AbstractLanguageSnippetTestsEngine() {
           .addCertificates(FileTestUtils.selfSignedCertificate)
           .buildLazily()
       )
+      .setPowerAssertionsEnabled(true)
   }
 
   override val testClass: KClass<*> = LanguageSnippetTests::class
@@ -200,6 +201,7 @@ class LanguageSnippetTestsEngine : AbstractLanguageSnippetTestsEngine() {
                     null,
                     StackFrameTransformers.empty,
                     mapOf(),
+                    true, // enable power assertions for tests
                   )
                 securityManager = null
                 applyFromProject(project)