Check that the tests run on the JDK the jdk job asked for

FormatterVersionTest, from palantir#1707, compares the
test JVM with the expectedJavaVersion system property, which upstream's
testJdkNN tasks set. Here the build passes the -PjavaRuntime value, so a CI
leg that runs on another JDK fails instead of skipping the tests that need
a newer parser and still passing.

Author: abashev

build.gradle

@@ -127,9 +127,11 @@ subprojects {
     }
 }
 
+// The JDK the tests run on, and with it the javac whose internals the formatter parses with. The code is
+// compiled for 21 whatever this says. CI's `jdk` jobs pass -PjavaRuntime=25 and so on.
+ext.javaRuntime = providers.gradleProperty('javaRuntime').getOrElse('21')
+
 javaVersions {
     libraryTarget = 21
-    // The JDK the tests run on, and with it the javac whose internals the formatter parses with. The code is
-    // compiled for 21 whatever this says. CI's `jdk` jobs pass -PjavaRuntime=25 and so on.
-    runtime = providers.gradleProperty('javaRuntime').getOrElse('21')
+    runtime = javaRuntime
 }

open-java-format/build.gradle

@@ -76,6 +76,9 @@ tasks.named("test") {
     // Run all classes and tests in parallel
     // https://junit.org/junit5/docs/current/user-guide/#writing-tests-parallel-execution
     systemProperty 'junit.jupiter.execution.parallel.mode.default', 'concurrent'
+    // FormatterVersionTest fails when the tests run on another JDK than the one asked for, so a CI leg
+    // cannot pass on the wrong JDK and skip the tests that need a newer parser.
+    systemProperty 'expectedJavaVersion', rootProject.ext.javaRuntime
 }
 
 javaVersion {

open-java-format/src/test/java/com/palantir/javaformat/java/FormatterVersionTest.java

@@ -22,15 +22,15 @@
 import org.junit.jupiter.api.Test;
 
 /**
- * Guards the {@code testJdkNN} legs: without this, a leg that resolves to a JDK older than the one it asked for skips
- * the {@code ModuleImport} golden and the module import tests, and still passes.
+ * Guards CI's {@code jdk} legs: without this, a leg that runs on an older JDK than the one it asked for with
+ * {@code -PjavaRuntime} skips the {@code ModuleImport} golden and the module import tests, and still passes.
  */
 public class FormatterVersionTest {
 
     @Test
     public void runsOnTheJdkTheTestTaskAskedFor() {
         String expected = System.getProperty("expectedJavaVersion");
-        Assumptions.assumeTrue(expected != null, "expectedJavaVersion is set only by the testJdkNN tasks");
+        Assumptions.assumeTrue(expected != null, "expectedJavaVersion is set by the Gradle build");
         assertThat(Formatter.getRuntimeVersion()).isEqualTo(Integer.parseInt(expected));
     }
 }