ci: standardize JDK usage

.github/workflows/downstream_build.yml

@@ -32,8 +32,12 @@ jobs:
     permissions:
       contents: read
     concurrency:
-      group: downstream-${{ inputs.repository }}-${{ github.event_name }}-${{ inputs.head_ref }}
+      group: downstream-${{ inputs.repository }}-${{ github.event_name }}-${{ inputs.head_ref }}-${{ matrix.java-version }}
       cancel-in-progress: true
+    strategy:
+      fail-fast: false # A broken JDK must not cancel the others.
+      matrix:
+        java-version: [ 25, 27 ] # Current LTS and latest JDK; replace 27 on each JDK release.
     timeout-minutes: 120
     steps:
       # Clone timefold-solver
@@ -89,10 +93,10 @@ jobs:
           path: ./${{ inputs.repository }}
           fetch-depth: 0
 
-      - name: Setup Temurin 25 and Maven
+      - name: Setup Temurin and Maven
         uses: actions/setup-java@v6.0.1
         with:
-          java-version: '25'
+          java-version: ${{ matrix.java-version }}
           distribution: 'temurin'
           cache: 'maven'
 

.github/workflows/pull_request.yml

@@ -26,10 +26,11 @@ jobs:
     permissions:
       contents: read
     strategy:
+      fail-fast: false # A broken JDK must not cancel the others.
       matrix:
         os: [ ubuntu-latest, ubuntu-24.04-arm, macos-latest, windows-latest ]
-        java-version: [ 25 ] # Latest LTS if not Ubuntu
-        include:
+        java-version: [ 25, 27 ] # Current LTS and latest JDK; replace 27 on each JDK release.
+        include: # Compile target and minimum runtime; Linux only.
           - os: ubuntu-latest
             java-version: 21
           - os: ubuntu-24.04-arm
@@ -85,10 +86,11 @@ jobs:
     permissions:
       contents: read
     strategy:
+      fail-fast: false # A broken JDK must not cancel the others.
       matrix:
         os: [ ubuntu-latest, ubuntu-24.04-arm ] # Windows doesn't work, Mac is not a deploy OS.
         module: ["spring-integration", "quarkus-integration"]
-        java-version: [ 25 ] # We only test Quarkus with the latest native image.
+        java-version: [ 25 ] # GraalVM only available for LTS.
     timeout-minutes: 120
     steps:
       - uses: actions/checkout@v7

.github/workflows/pull_request_quickstarts.yml

@@ -27,8 +27,12 @@ jobs:
     permissions:
       contents: read
     concurrency:
-      group: downstream-quickstarts-${{ github.event_name }}-${{ github.head_ref }}
+      group: downstream-quickstarts-${{ github.event_name }}-${{ github.head_ref }}-${{ matrix.java-version }}
       cancel-in-progress: true
+    strategy:
+      fail-fast: false # A broken JDK must not cancel the others.
+      matrix:
+        java-version: [ 25, 27 ] # Current LTS and latest JDK; replace 27 on each JDK release.
     timeout-minutes: 120
     steps:
       # Clone timefold-solver
@@ -60,10 +64,10 @@ jobs:
           fetch-depth: 0 # Otherwise merge will fail on account of not having history.
 
       # Build and test
-      - name: Setup Temurin 25 and Maven
+      - name: Setup Temurin and Maven
         uses: actions/setup-java@v6.0.1
         with:
-          java-version: '25'
+          java-version: ${{ matrix.java-version }}
           distribution: 'temurin'
           cache: 'maven'
       - name: Quickly build timefold-solver

.github/workflows/pull_request_secure.yml

@@ -70,8 +70,13 @@ jobs:
     permissions:
       contents: read
     concurrency:
-      group: downstream-enterprise-${{ github.event_name }}-${{ github.head_ref }}
+      group: downstream-enterprise-${{ github.event_name }}-${{ github.head_ref }}-${{ matrix.java-version }}
       cancel-in-progress: true
+    strategy:
+      fail-fast: false # A broken JDK must not cancel the others.
+      matrix:
+        # Compile target, current LTS and latest JDK; replace 27 on each JDK release.
+        java-version: [ 21, 25, 27 ]
     timeout-minutes: 120
     steps:
       # Clone timefold-solver
@@ -107,10 +112,10 @@ jobs:
           fetch-depth: 0 # Otherwise merge will fail on account of not having history.
 
       # Build and test
-      - name: Setup Temurin 21 and Maven
+      - name: Setup Temurin and Maven
         uses: actions/setup-java@v6.0.1
         with:
-          java-version: '21'
+          java-version: ${{ matrix.java-version }}
           distribution: 'temurin'
           cache: 'maven'
       - name: Quickly build timefold-solver
@@ -140,10 +145,11 @@ jobs:
     permissions:
       contents: read
     strategy:
+      fail-fast: false # A broken JDK must not cancel the others.
       matrix:
         os: [ ubuntu-latest, ubuntu-24.04-arm ] # Windows doesn't work, Mac is not a deploy OS.
         module: [ "spring-boot", "quarkus" ]
-        java-version: [ 25 ] # We only test Quarkus with the latest native image.
+        java-version: [ 25 ] # GraalVM only available for LTS.
     timeout-minutes: 120
     steps:
       # Clone timefold-solver

core/src/test/java/ai/timefold/solver/core/impl/score/stream/collector/bi/InnerBiConstraintCollectorsTest.java

@@ -1590,7 +1590,7 @@ private static <Container_> void assertUnfairness(
         LoadBalance<String> actualResult = collector.finisher().apply((Container_) container);
         assertThat(actualResult.unfairness())
                 .as("Collector (" + collector + ") did not produce expected result.")
-                .isEqualTo(expectedValue);
+                .isEqualByComparingTo(expectedValue); // Scale-safe comparison.
     }
 
 }

core/src/test/java/ai/timefold/solver/core/impl/score/stream/collector/quad/InnerQuadConstraintCollectorsTest.java

@@ -1636,7 +1636,7 @@ private static <Container_> void assertUnfairness(
         LoadBalance<String> actualResult = collector.finisher().apply((Container_) container);
         assertThat(actualResult.unfairness())
                 .as("Collector (" + collector + ") did not produce expected result.")
-                .isEqualTo(expectedValue);
+                .isEqualByComparingTo(expectedValue); // Scale-safe comparison.
     }
 
 }

core/src/test/java/ai/timefold/solver/core/impl/score/stream/collector/tri/InnerTriConstraintCollectorsTest.java

@@ -1593,7 +1593,7 @@ private static <Container_> void assertUnfairness(
         LoadBalance<String> actualResult = collector.finisher().apply((Container_) container);
         assertThat(actualResult.unfairness())
                 .as("Collector (" + collector + ") did not produce expected result.")
-                .isEqualTo(expectedValue);
+                .isEqualByComparingTo(expectedValue); // Scale-safe comparison.
     }
 
 }

core/src/test/java/ai/timefold/solver/core/impl/score/stream/collector/uni/InnerUniConstraintCollectorsTest.java

@@ -1049,7 +1049,7 @@ private static <Container_> void assertUnfairness(
         LoadBalance<String> actualResult = collector.finisher().apply((Container_) container);
         assertThat(actualResult.unfairness())
                 .as("Collector (" + collector + ") did not produce expected result.")
-                .isEqualTo(expectedValue);
+                .isEqualByComparingTo(expectedValue); // Scale-safe comparison.
     }
 
     @Test

docs/src/modules/ROOT/pages/upgrading-timefold-solver/framework-version-warning.adoc

@@ -1,5 +1,2 @@
-[NOTE]
-====
-Our automatic migrations will not change the version of your frameworks.
+NOTE: Our automatic migrations will not change the version of your frameworks.
 If you run into compatibility issues, please consult the integration guides for xref:running-timefold-solver/library/spring-boot.adoc#integrationWithSpringBoot[Spring] or xref:running-timefold-solver/library/quarkus.adoc#integrationWithQuarkus[Quarkus].
-====

docs/src/modules/ROOT/pages/upgrading-timefold-solver/migration-jdk-warning.adoc

@@ -0,0 +1 @@
+NOTE: The migration tool only works on JDK 25 or earlier, because OpenRewrite only supports LTS versions of Java.

docs/src/modules/ROOT/pages/upgrading-timefold-solver/upgrade-from-v1.adoc

@@ -52,6 +52,8 @@ curl https://raw.githubusercontent.com/TimefoldAI/timefold-solver/refs/tags/v{ti
 
 include::framework-version-warning.adoc[leveloffset=+1]
 
+include::migration-jdk-warning.adoc[]
+
 Having done that, you can check the local changes and commit them.
 
 For the time being, Kotlin users need to follow the upgrade recipe and apply the steps manually.

docs/src/modules/ROOT/pages/upgrading-timefold-solver/upgrade-to-latest.adoc

@@ -55,6 +55,8 @@ curl https://raw.githubusercontent.com/TimefoldAI/timefold-solver/refs/tags/v{ti
 
 include::framework-version-warning.adoc[leveloffset=+1]
 
+include::migration-jdk-warning.adoc[]
+
 Having done that, you can check the local changes and commit them.
 
 For the time being, Kotlin users need to follow the upgrade recipe and apply the steps manually.

tools/migration/pom.xml

@@ -16,6 +16,7 @@
   <description>
     Upgrade your code with a single command.
     This migration replaces all your calls to deleted/deprecated methods of Timefold with their proper alternatives.
+    Only runs on JDK 25 or older, on account of OpenRewrite only supporting LTS Java versions.
   </description>
   <url>https://solver.timefold.ai</url>
 

tools/migration/src/test/java/ai/timefold/solver/migration/AbstractRecipeTest.java

@@ -0,0 +1,19 @@
+package ai.timefold.solver.migration;
+
+import static org.junit.jupiter.api.Assumptions.assumeTrue;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.parallel.Execution;
+import org.junit.jupiter.api.parallel.ExecutionMode;
+import org.openrewrite.test.RewriteTest;
+
+@Execution(ExecutionMode.CONCURRENT)
+public abstract class AbstractRecipeTest implements RewriteTest {
+
+    @BeforeAll
+    static void skipOnUnsupportedJdk() {
+        // OpenRewrite supports only LTS JDKs.
+        assumeTrue(Runtime.version().feature() <= 25, "OpenRewrite does not support JDK > 25.");
+    }
+
+}

tools/migration/src/test/java/ai/timefold/solver/migration/ChangeVersionRecipeTest.java

@@ -3,13 +3,9 @@
 import static org.openrewrite.maven.Assertions.pomXml;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 
-@Execution(ExecutionMode.CONCURRENT)
-class ChangeVersionRecipeTest implements RewriteTest {
+class ChangeVersionRecipeTest extends AbstractRecipeTest {
 
     private final ChangeVersionRecipe recipe = new ChangeVersionRecipe();
 

tools/migration/src/test/java/ai/timefold/solver/migration/preview/NeighborhoodsMigrationRecipeTest.java

@@ -4,18 +4,15 @@
 
 import java.util.List;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
 import ai.timefold.solver.migration.NoWildCardImportStyle;
 
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class NeighborhoodsMigrationRecipeTest implements RewriteTest {
+class NeighborhoodsMigrationRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/AsConstraintRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class AsConstraintRecipeTest implements RewriteTest {
+class AsConstraintRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/ConstraintRefRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class ConstraintRefRecipeTest implements RewriteTest {
+class ConstraintRefRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/NullableRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class NullableRecipeTest implements RewriteTest {
+class NullableRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/RemoveConstraintPackageRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class RemoveConstraintPackageRecipeTest implements RewriteTest {
+class RemoveConstraintPackageRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/ScoreGettersRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class ScoreGettersRecipeTest implements RewriteTest {
+class ScoreGettersRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/ScoreManagerMethodsRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class ScoreManagerMethodsRecipeTest implements RewriteTest {
+class ScoreManagerMethodsRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {

tools/migration/src/test/java/ai/timefold/solver/migration/v1/SingleConstraintAssertionRecipeTest.java

@@ -2,16 +2,14 @@
 
 import static org.openrewrite.java.Assertions.java;
 
+import ai.timefold.solver.migration.AbstractRecipeTest;
+
 import org.junit.jupiter.api.Test;
-import org.junit.jupiter.api.parallel.Execution;
-import org.junit.jupiter.api.parallel.ExecutionMode;
 import org.openrewrite.java.JavaParser;
 import org.openrewrite.test.RecipeSpec;
-import org.openrewrite.test.RewriteTest;
 import org.openrewrite.test.TypeValidation;
 
-@Execution(ExecutionMode.CONCURRENT)
-class SingleConstraintAssertionRecipeTest implements RewriteTest {
+class SingleConstraintAssertionRecipeTest extends AbstractRecipeTest {
 
     @Override
     public void defaults(RecipeSpec spec) {