Expand TestNG to AssertJ assertion coverage by juherr · Pull Request #1028 · openrewrite/rewrite-testing-frameworks

juherr · 2026-06-19T12:00:28Z

What's changed

Widen org.openrewrite.java.testing.testng.TestNgToAssertj from "scalar assertEquals/assertNotEquals + Refaster basics" to full coverage of every static method on org.testng.Assert (verified against TestNG 7.12.0).

New recipes

Recipe	TestNG → AssertJ
`TestNgAssertSameToAssertThat`	`assertSame(a, b)` → `assertThat(a).isSameAs(b)`
`TestNgAssertNotSameToAssertThat`	`assertNotSame(a, b)` → `assertThat(a).isNotSameAs(b)`
`TestNgAssertThrowsToAssertThat`	`assertThrows(Type.class, run)`/`expectThrows(...)` → `assertThatExceptionOfType(Type.class).isThrownBy(run)` (`.actual()` when the result is used); `assertThrows(run)` → `assertThatThrownBy(run)`
`TestNgAssertEqualsNoOrderToAssertThat`	`assertEqualsNoOrder(...)` → `containsExactlyInAnyOrder` / `containsExactlyInAnyOrderElementsOf` (arrays, collections, iterators)
`TestNgAssertEqualsDeepToAssertThat`	`assertEqualsDeep`/`assertNotEqualsDeep` (Map/Set) → `usingRecursiveComparison().isEqualTo()`/`.isNotEqualTo()`
`TestNgAssertListToAssertThat`	`assertListContainsObject`/`assertListNotContainsObject` → `.contains()`/`.doesNotContain()`; predicate-based `assertListContains`/`assertListNotContains` → `.anyMatch()`/`.noneMatch()`

Fix to existing `assertEquals`/`assertNotEquals`

TestNgAssertEqualsToAssertThat matched all assertEquals(..) overloads and always emitted isEqualTo(...) — wrong for the structural overloads (for Iterator/Iterable it compared object identity rather than TestNG's element-wise semantics). It now dispatches on the actual argument's type:

arrays → containsExactly
Set → containsExactlyInAnyOrderElementsOf
other Iterable (List/Collection) → containsExactlyElementsOf
Iterator → assertThat(actual).toIterable().containsExactlyElementsOf(() -> expected)
Map / scalars → isEqualTo (unchanged, already correct)

Both assertEquals and assertNotEquals also gained an integral-actual + floating-delta guard (mirroring JUnitAssertEqualsToAssertThat) so an int/long actual with a floating delta falls back to isEqualTo/isNotEqualTo instead of an uncompilable isCloseTo.

Coverage

After this PR, every static method on org.testng.Assert is handled:

Dedicated Java recipes: assertEquals, assertNotEquals, assertEqualsDeep, assertNotEqualsDeep, assertEqualsNoOrder, assertSame, assertNotSame, assertThrows, expectThrows, assertListContains(Object), assertListNotContains(Object).
Picnic Refaster rules (kept): assertTrue, assertFalse, assertNull, assertNotNull, fail.

Notes

All new recipes are registered in testng.yml and have a mirror *Test with a single @DocumentExample.
recipes.csv was regenerated via ./gradlew recipeCsvGenerate (not hand-edited).
The message argument maps to .as(...), consistent with the existing TestNG recipes. The known .as(...) vs .withFailMessage(...) divergence with the Picnic Refaster path is documented as future work in a comment in testng.yml rather than resolved here.

Test plan

./gradlew build — green (license check, recipes.csv completeness, full test suite).
Includes regression coverage that assertEquals(List, List) now produces containsExactlyElementsOf rather than isEqualTo, and that the Iterator overloads of assertEquals/assertEqualsNoOrder produce compilable toIterable()-based assertions.

Add dedicated recipes for assertSame/assertNotSame, assertThrows/expectThrows, assertEqualsNoOrder, and assertEqualsDeep/assertNotEqualsDeep, and fix assertEquals/assertNotEquals to use element-wise assertions (containsExactly, containsExactlyElementsOf, toIterable) for arrays, collections, sets and iterators instead of a reference-level isEqualTo. Each recipe is registered in testng.yml and covered by a mirror test with a @DocumentExample.

Cover the remaining org.testng.Assert static assertions: assertListContainsObject /assertListNotContainsObject map to assertThat(list).contains()/.doesNotContain(), and the predicate-based assertListContains/assertListNotContains map to .anyMatch()/.noneMatch().

…cipes Call super.visitMethodInvocation() before matching so assertions nested inside non-matching invocations (e.g. within a lambda argument) are still visited and migrated. Brings the TestNG recipes and JUnitFailToAssertJFail in line with the recursing pattern already used elsewhere.

timtebeek

Thanks a lot for your efforts here, especially considering where you're coming from! I've pushed one small change to handle nested cases too, but other than that the work looks solid here. Thanks for applying your in depth knowledge of mappings to complete the migration.

I hope all is well there; let me know if you'd like an expedited release to get this out. Otherwise our next scheduled release will be in two weeks.

juherr · 2026-06-19T13:05:34Z

To be honest, Claude did most of the work here, and I expect it to be good enough.

We'll see how it holds up once the community starts testing it.

Please ping me when the release is available, and I'll add the corresponding documentation on the TestNG side.

timtebeek · 2026-06-19T14:24:47Z

To be honest, Claude did most of the work here, and I expect it to be good enough.

Hah no worries; I'd recognized the signatures already indeed, and knew what to look for in the review. Still helpful!

We'll see how it holds up once the community starts testing it.

Please ping me when the release is available, and I'll add the corresponding documentation on the TestNG side.

Sure! I've put out release right now that's already up at Maven Central:
https://github.com/openrewrite/rewrite-testing-frameworks/releases/tag/v3.39.0

Send a link when you have any messaging up that you'd like me to have a look over.

timtebeek · 2026-06-20T20:07:55Z

Thanks for the continued reports and contributions! I've expanded coverage quite a bit today following your reports:

v3.39.0...main

Let me know if you plan any further validation (potentially using our snapshot versions), before I cut another release to get these fixes out.

juherr · 2026-06-21T08:59:11Z

Validated against the full TestNG suite using org.openrewrite.recipe:rewrite-testing-frameworks:3.40.0-SNAPSHOT (recipe org.openrewrite.java.testing.assertj.Assertj, OpenRewrite Gradle plugin 7.35.0, JDK 21) — we validate all the changes. 🎉

The four reported issues now transform exactly as expected:

Issue	Before	After (snapshot)
#1029	`Assert.assertEquals("a", "b")`	`assertThat("a").isEqualTo("b")` + `import static …assertThat`
#1030	`assertThat(x instanceof String).isTrue()` / `.isFalse()`	`.isInstanceOf(String.class)` / `.isNotInstanceOf(String.class)`
#1031	`assertThat(4).isEqualTo(list.size())`	`assertThat(list).hasSize(4)`
#1032	`assertThat(v).isNotSameAs(0)` / `.isSameAs(1)`	`.isNotZero()` / `.isOne()` — in a single run ✅

Running it over our already-migrated suite produced only correct simplifications, no regressions — and the new rules even caught cases our manual pass had missed, e.g. array length:

assertThat(arr.length).isEqualTo(2);                  // -> assertThat(arr).hasSize(2);
assertThat(arr.length).isZero();                      // -> assertThat(arr).isEmpty();
assertThat(passedTests.length).isEqualTo(passed.size()); // -> assertThat(passedTests).hasSameSizeAs(passed);

Good to go for a release from our side. One item is out of scope for this repo and tracked upstream: isSameAs/isNotSameAs on reference types (e.g. two java.util.Date) is still rewritten to isEqualTo/isNotEqualTo by the bundled AssertJPrimitiveRules — PicnicSupermarket/error-prone-support#2277. Not part of these changes; just flagging it for whenever a newer error-prone-support is pulled in.

Thanks again for the quick turnaround on all of these!

timtebeek · 2026-06-21T20:08:58Z

Perfect, thanks for confirming, and thanks again for the helpful reports!

I've just triggered the release, that should be out on Maven central in 30 minutes:

https://github.com/openrewrite/rewrite-testing-frameworks/releases/tag/v3.40.0

juherr added 2 commits June 19, 2026 13:40

moderne-meeseeks Bot added this to OpenRewrite Jun 19, 2026

moderne-meeseeks Bot assigned juherr Jun 19, 2026

github-project-automation Bot moved this to In Progress in OpenRewrite Jun 19, 2026

timtebeek self-requested a review June 19, 2026 12:06

timtebeek added assertj recipe Recipe request labels Jun 19, 2026

timtebeek moved this from In Progress to Ready to Review in OpenRewrite Jun 19, 2026

juherr mentioned this pull request Jun 19, 2026

Assert.assertEquals(String, String, String) to show diff testng-team/testng-asserts#18

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timtebeek approved these changes Jun 19, 2026

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timtebeek merged commit 665bd84 into openrewrite:main Jun 19, 2026
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github-project-automation Bot moved this from Ready to Review to Done in OpenRewrite Jun 19, 2026

juherr deleted the testng-assertj-assertion-coverage branch June 19, 2026 13:05

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Expand TestNG to AssertJ assertion coverage#1028

Expand TestNG to AssertJ assertion coverage#1028
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juherr commented Jun 19, 2026

What's changed

New recipes

Fix to existing assertEquals/assertNotEquals

Coverage

Notes

Test plan

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Fix to existing `assertEquals`/`assertNotEquals`