Excavator: Migrate Groovy nebula test PalantirJavaFormatSpotlessPluginTest to the new Java Junit framework

MIGRATION_SUMMARY.md

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+# Test Migration Summary
+
+## Overview
+Successfully migrated `PalantirJavaFormatSpotlessPluginTest` from Groovy/Spock to Java/JUnit 5 using the new gradle-plugin-testing framework.
+
+## Files Changed
+
+### Original File
+- **Path**: `/repo/gradle-palantir-java-format/src/test/groovy/com/palantir/javaformat/gradle/PalantirJavaFormatSpotlessPluginTest.groovy`
+- **Status**: Enhanced with delineator comments for review comparison
+- **Action**: Can be deleted once the migration is approved
+
+### Migrated File
+- **Path**: `/repo/gradle-palantir-java-format/src/test/groovy/com/palantir/javaformat/gradle/PalantirJavaFormatSpotlessPluginTest.java`
+- **Note**: The file is in the `groovy` directory (not `java`) because it needs to access `GradlewExecutor.java` which is also in the groovy directory
+
+### Artifact Files
+- **test-migration-errors.md**: Documents all errors encountered and fixes applied during migration
+- **MIGRATION_SUMMARY.md**: This file - summary of the migration
+
+## Key Changes
+
+### 1. Test Framework
+- **From**: Spock with `@Unroll` and `where` clauses
+- **To**: JUnit 5 with `@ParameterizedTest` and `@MethodSource`
+
+### 2. Test Structure
+```java
+// Old (Spock)
+@Unroll
+def "formats with spotless when spotless is applied"(String extraGradleProperties, String javaVersion, String expectedOutput) {
+    // ... test body ...
+    where:
+    extraGradleProperties               | javaVersion   | expectedOutput
+    ""                                  | 21            | "Using the Java-based formatter"
+    "palantir.native.formatter=true"    | 21            | "Using the Java-based formatter"
+}
+
+// New (JUnit 5)
+@ParameterizedTest(name = "[{index}] extraGradleProperties={0}, javaVersion={1}, expectedOutput={2}")
+@MethodSource("formatsWithSpotlessTestCases")
+void formats_with_spotless_when_spotless_is_applied(
+        String extraGradleProperties, String javaVersion, String expectedOutput,
+        GradleInvoker gradle, RootProject rootProject) {
+    // ... test body ...
+}
+
+static Stream<Arguments> formatsWithSpotlessTestCases() {
+    return Stream.of(
+            Arguments.of("", "21", "Using the Java-based formatter"),
+            Arguments.of("palantir.native.formatter=true", "21", "Using the Java-based formatter"),
+            Arguments.of("palantir.native.formatter=true", "17", "Using the native-image formatter"));
+}
+```
+
+### 3. File Operations
+- **From**: Direct file manipulation (`settingsFile << '...'`, `buildFile << '...'`, `file('...').text = ...`)
+- **To**: Fluent API (`rootProject.settingsGradle().append(...)`, `rootProject.buildGradle().append(...)`, `rootProject.file(...).overwrite(...)`)
+
+### 4. Assertions
+- **From**: Spock's built-in assertions
+- **To**: AssertJ assertions (`assertThat(output).contains(...)`, `assertThat(formattedFile).isEqualTo(...)`)
+
+### 5. Test Naming
+- **From**: Spock string test names with spaces
+- **To**: snake_case method names (`formats_with_spotless_when_spotless_is_applied`)
+
+### 6. Setup Method
+- **From**: `def setup()` with implicit projectDir access
+- **To**: `@BeforeEach void setup(RootProject rootProject)` with parameter injection
+
+## Important Notes
+
+### Custom Executor Usage
+This test uses a custom `GradlewExecutor` rather than the standard `GradleInvoker` because:
+1. It needs special classpath handling to avoid loading formatter classes twice
+2. It runs the actual `./gradlew` wrapper command (not Gradle TestKit)
+3. The test calls `gradle.withArgs("wrapper").buildsSuccessfully()` to generate the wrapper first
+
+### File Location Decision
+The migrated Java test was placed in `src/test/groovy/` instead of `src/test/java/` because:
+- Gradle's groovy plugin compiles `src/test/java/` before `src/test/groovy/`
+- `GradlewExecutor.java` is located in `src/test/groovy/`
+- Java files in `src/test/java/` cannot access classes in `src/test/groovy/` during compilation
+- Both Java and Groovy files in the groovy directory compile together successfully
+
+## Compilation Status
+✅ **PASSED**: `./gradlew :gradle-palantir-java-format:compileTestGroovy`
+
+The test compiles successfully and is ready for testing.
+
+## Delineator Comments
+Both the original Groovy file and the new Java file contain `***DELINEATOR FOR REVIEW` comments to help reviewers compare:
+- Method boundaries
+- Variable/field definitions
+- Test method sections (setup/when/then)
+
+These comments can be removed after the migration is approved.