Migrate test Groovy files to Java using JUnit 5
- List all Groovy files of the current Gradle module
- Convert Groovy files to Java using JUnit 5
- Make sure the tests are still passing after migration and that the test count has not changed
- Remove Groovy files
When converting Groovy code to Java code, make sure that:
- The Java code generated is compatible with JDK 8
- When translating Spock tests, prefer
@TableTest for data rows that are naturally tabular. See detailed guidance in the "TableTest usage" section.
@TableTest and @MethodSource may be combined on the same @ParameterizedTest when most cases are tabular but a few cases require programmatic setup.
- In combined mode, keep table-friendly cases in
@TableTest, and put only non-tabular/complex cases in @MethodSource.
- If
@TableTest is not viable for the test at all, use @MethodSource only.
- If
@TableTest was successfully used and if the @ParameterizedTest is not used to specify the test name, @ParameterizedTest can then be removed as @TableTest replace it fully.
- For
@MethodSource, name the arguments method <testMethodName>Arguments (camelCase, e.g. testMethodArguments) and return Stream<Arguments> using Stream.of(...) and arguments(...) with static import.
- Ensure parameterized test names are human-readable (i.e. no hashcodes); instead add a description string as the first
Arguments.arguments(...) value or index the test case
- When converting tuples, create a light dedicated structure instead to keep the typing system
- Instead of checking a state and throwing an exception, use JUnit asserts
- Instead of using
assertTrue(a.equals(b)) or assertFalse(a.equals(b)), use assertEquals(expected, actual) and assertNotEquals(unexpected, actual)
- Import frequently used types rather than using fully-qualified names inline, to improve readability
- Do not wrap checked exceptions and throw a Runtime exception; prefer adding a throws clause at method declaration
- Do not mark local variables
final
- Ensure variables are human-readable; avoid single-letter names and pre-define variables that are referenced multiple times
- When translating Spock
Mock(...) usage, use libs.bundles.mockito instead of writing manual recording/stub implementations
- Replace
injectSysConfig(key, value) calls with @WithConfig when the key and value are static literals. Put it on the test method for per-test config, or on the class when every test needs it. The dd. prefix is added automatically — use the bare key (e.g. "trace.scope.strict.mode", not "dd.trace.scope.strict.mode"). For dynamic or parameterized values, keep the imperative WithConfigExtension.injectSysConfig(key, value) call.
- Keep inline comments
- Migrate the named Spock clauses if they exist as inline comments in the Java unit test
- When Groovy tests navigate a JSON request body through helpers like
asMap() / asLong() / asList(), check whether json-unit-assertj (libs.json.unit.assertj) is already in the module's build file. If it is, add a method that returns the raw JSON string and use assertThatJson(json).node("some.nested.field").isEqualTo(value) directly instead of the map traversal.
- Groovy's
[key: val] map literals use a LinkedHashMap. When the test doesn't care about insertion order, use singletonMap for a single entry or HashMap for two or more. If a helper method builds these maps, add a two-arg overload rather than scattering new LinkedHashMap<>() constructions through test bodies.
TableTest usage
Import: import org.tabletest.junit.TableTest;
JDK 8 rules:
- No text blocks.
- @TableTest must use String[] annotation array syntax:
@TableTest({ "a | b", "1 | 2" })
Spock where: → @TableTest:
- First row = header (column names = method parameters).
- Add scenario column as first column (display name, not a method parameter).
- Use | delimiter; align columns so pipes line up vertically.
- Prefer single quotes for strings with special chars (e.g., 'a|b', '[]').
- Blank cell = null (object types); '' = empty string.
- Collections: [a, b] = List/array, {a, b} = Set, [k: v] = Map.
Mixed eligibility:
- Prefer combining @TableTest + @MethodSource on one @ParameterizedTest when only some cases are complex.
- Use @MethodSource only when tabular representation is not practical for the test.
Do NOT use @TableTest when:
- Majority of rows require complex objects or custom converters.
Quality rules (apply during generation)
Before writing any Java output, read .claude/skills/migrate-groovy-to-java/QUALITY_RULES.md in full.
Apply all BLOCKER rules unconditionally.
Apply WARNING rules unless they require creating utility classes that do not yet exist.
Apply STYLE rules where they improve clarity without added complexity.
1---2name: migrate-groovy-to-java3description: Converts Spock/Groovy test files in a Gradle module to equivalent JUnit 5 Java tests. Use when asked to "migrate groovy", "convert groovy to java", "g2j", or when a module has .groovy test files that need to be replaced with .java equivalents.4---56Migrate test Groovy files to Java using JUnit 5781. List all Groovy files of the current Gradle module92. Convert Groovy files to Java using JUnit 5103. Make sure the tests are still passing after migration and that the test count has not changed114. Remove Groovy files1213When converting Groovy code to Java code, make sure that:14- The Java code generated is compatible with JDK 815- When translating Spock tests, prefer `@TableTest` for data rows that are naturally tabular. See detailed guidance in the "TableTest usage" section.16- `@TableTest` and `@MethodSource` may be combined on the same `@ParameterizedTest` when most cases are tabular but a few cases require programmatic setup.17- In combined mode, keep table-friendly cases in `@TableTest`, and put only non-tabular/complex cases in `@MethodSource`.18- If `@TableTest` is not viable for the test at all, use `@MethodSource` only.19- If `@TableTest` was successfully used and if the `@ParameterizedTest` is not used to specify the test name, `@ParameterizedTest` can then be removed as `@TableTest` replace it fully.20- For `@MethodSource`, name the arguments method `<testMethodName>Arguments` (camelCase, e.g. `testMethodArguments`) and return `Stream<Arguments>` using `Stream.of(...)` and `arguments(...)` with static import.21- Ensure parameterized test names are human-readable (i.e. no hashcodes); instead add a description string as the first `Arguments.arguments(...)` value or index the test case22- When converting tuples, create a light dedicated structure instead to keep the typing system23- Instead of checking a state and throwing an exception, use JUnit asserts24- Instead of using `assertTrue(a.equals(b))` or `assertFalse(a.equals(b))`, use `assertEquals(expected, actual)` and `assertNotEquals(unexpected, actual)`25- Import frequently used types rather than using fully-qualified names inline, to improve readability26- Do not wrap checked exceptions and throw a Runtime exception; prefer adding a throws clause at method declaration27- Do not mark local variables `final`28- Ensure variables are human-readable; avoid single-letter names and pre-define variables that are referenced multiple times29- When translating Spock `Mock(...)` usage, use `libs.bundles.mockito` instead of writing manual recording/stub implementations30- Replace `injectSysConfig(key, value)` calls with `@WithConfig` when the key and value are static literals. Put it on the test method for per-test config, or on the class when every test needs it. The `dd.` prefix is added automatically — use the bare key (e.g. `"trace.scope.strict.mode"`, not `"dd.trace.scope.strict.mode"`). For dynamic or parameterized values, keep the imperative `WithConfigExtension.injectSysConfig(key, value)` call.31- Keep inline comments32- Migrate the named Spock clauses if they exist as inline comments in the Java unit test33- When Groovy tests navigate a JSON request body through helpers like `asMap()` / `asLong()` / `asList()`, check whether `json-unit-assertj` (`libs.json.unit.assertj`) is already in the module's build file. If it is, add a method that returns the raw JSON string and use `assertThatJson(json).node("some.nested.field").isEqualTo(value)` directly instead of the map traversal.34- Groovy's `[key: val]` map literals use a `LinkedHashMap`. When the test doesn't care about insertion order, use `singletonMap` for a single entry or `HashMap` for two or more. If a helper method builds these maps, add a two-arg overload rather than scattering `new LinkedHashMap<>()` constructions through test bodies.3536TableTest usage37 Import: `import org.tabletest.junit.TableTest;`3839 JDK 8 rules:40 - No text blocks.41 - @TableTest must use String[] annotation array syntax:42 ```43 @TableTest({44 "a | b",45 "1 | 2"46 })47 ```4849 Spock `where:` → @TableTest:50 - First row = header (column names = method parameters).51 - Add `scenario` column as first column (display name, not a method parameter).52 - Use `|` delimiter; align columns so pipes line up vertically.53 - Prefer single quotes for strings with special chars (e.g., `'a|b'`, `'[]'`).54 - Blank cell = null (object types); `''` = empty string.55 - Collections: `[a, b]` = List/array, `{a, b}` = Set, `[k: v]` = Map.5657 Mixed eligibility:58 - Prefer combining `@TableTest` + `@MethodSource` on one `@ParameterizedTest` when only some cases are complex.59 - Use `@MethodSource` only when tabular representation is not practical for the test.6061 Do NOT use @TableTest when:62 - Majority of rows require complex objects or custom converters.6364## Quality rules (apply during generation)6566Before writing any Java output, read `.claude/skills/migrate-groovy-to-java/QUALITY_RULES.md` in full.67Apply all BLOCKER rules unconditionally.68Apply WARNING rules unless they require creating utility classes that do not yet exist.69Apply STYLE rules where they improve clarity without added complexity.