Add junit-6-migration module: JUnit 5.14.4 vs 6.1.3, API diff and behaviour probes

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01YPgGH6aMbSLANL3E2HHmS6

junit-6-migration/src/test/java/com/ankurm/junitmigration/BehaviourTest.java

@@ -0,0 +1,86 @@
+package com.ankurm.junitmigration;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.platform.engine.discovery.DiscoverySelectors.selectClass;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+import org.junit.platform.engine.TestExecutionResult;
+import org.junit.platform.launcher.TestExecutionListener;
+import org.junit.platform.launcher.TestIdentifier;
+import org.junit.platform.launcher.core.LauncherDiscoveryRequestBuilder;
+import org.junit.platform.launcher.core.LauncherFactory;
+
+/**
+ * Runs the same probe classes on whichever JUnit is on the class path and writes what happened to
+ * output/NN-name-<version>.txt. The two versions are meant to give different answers in places, so this
+ * test records them instead of asserting them. It does assert that the probes ran at all.
+ */
+class BehaviourTest {
+
+    private static final String VERSION = System.getProperty("junit.version", "unknown");
+
+    @Test
+    void csvBehaviour() throws IOException {
+        List<String> lines = run(CsvProbe.class);
+        write("03-csv-behaviour", lines);
+        assertTrue(lines.size() > 10, "probe produced results");
+    }
+
+    @Test
+    void vintageStillRunsJUnit4() throws IOException {
+        List<String> lines = run(LegacyJUnit4Test.class);
+        write("04-vintage-junit4", lines);
+        assertTrue(lines.stream().anyMatch(l -> l.contains("stillRuns") && l.contains("SUCCESSFUL")), "junit 4 test ran");
+    }
+
+    private static List<String> run(Class<?> probe) {
+        List<String> lines = new ArrayList<>();
+        var request = LauncherDiscoveryRequestBuilder.request().selectors(selectClass(probe)).build();
+        var launcher = LauncherFactory.create();
+        launcher.execute(request, new TestExecutionListener() {
+            @Override
+            public void executionSkipped(TestIdentifier id, String reason) {
+                lines.add(String.format("%-11s %s -> %s", "SKIPPED", id.getDisplayName(), reason));
+            }
+
+            @Override
+            public void executionFinished(TestIdentifier id, TestExecutionResult result) {
+                // a parameterized method is a container: report it too when it fails as a whole
+                if (!id.isTest() && result.getStatus() == TestExecutionResult.Status.SUCCESSFUL) {
+                    return;
+                }
+                if (!id.isTest() && id.getParentId().isEmpty()) {
+                    return;
+                }
+                String outcome = result.getStatus().name();
+                String message = result.getThrowable().map(t -> " -> " + t.getClass().getSimpleName() + ": "
+                        + firstLine(t.getMessage())).orElse("");
+                lines.add(String.format("%-11s %s%s%s", outcome, id.isTest() ? "" : "[method] ", id.getDisplayName(), message));
+            }
+        });
+        return lines;
+    }
+
+    private static String firstLine(String s) {
+        if (s == null) {
+            return "";
+        }
+        String one = s.lines().findFirst().orElse("");
+        return one.length() > 110 ? one.substring(0, 110) + "..." : one;
+    }
+
+    private static void write(String name, List<String> lines) throws IOException {
+        Path dir = Path.of("output");
+        Files.createDirectories(dir);
+        List<String> out = new ArrayList<>();
+        out.add("JUnit " + VERSION);
+        out.addAll(lines);
+        Files.write(dir.resolve(name + "-" + VERSION + ".txt"), out);
+    }
+}

junit-6-migration/src/test/java/com/ankurm/junitmigration/CsvProbe.java

@@ -0,0 +1,56 @@
+package com.ankurm.junitmigration;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvFileSource;
+import org.junit.jupiter.params.provider.CsvSource;
+
+/**
+ * Not run by Surefire (the name does not end in Test). {@link BehaviourTest} launches it through the
+ * JUnit Platform Launcher and records what each invocation was called and whether it passed, on whichever
+ * JUnit version is on the class path.
+ */
+class CsvProbe {
+
+    @ParameterizedTest
+    @CsvSource({
+            "apple, 1",
+            "'a,b', 2",
+            "  padded  , 3",
+            "'', 4",
+            ", 5",
+            "NIL, 6",
+            "'it''s', 7",
+            "\"dq\", 8"
+    })
+    void basicRows(String name, int n) {
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"x;1", "y;2"}, delimiter = ';', useHeadersInDisplayName = false)
+    void customDelimiter(String name, int n) {
+    }
+
+    @ParameterizedTest
+    @CsvSource(textBlock = """
+            name, qty
+            widget, 4
+            'multi word', 5
+            """, useHeadersInDisplayName = true)
+    void textBlockWithHeader(String name, int qty) {
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"a,b,c"})
+    void tooManyColumnsForParameters(String first) {
+    }
+
+    @ParameterizedTest
+    @CsvSource(value = {"1234567890,1"}, maxCharsPerColumn = 5)
+    void columnLongerThanLimit(String value, int n) {
+    }
+
+    @ParameterizedTest
+    @CsvFileSource(resources = "/probe.csv", numLinesToSkip = 1)
+    void fileRows(String name, int n) {
+    }
+}

junit-6-migration/src/test/java/com/ankurm/junitmigration/LegacyJUnit4Test.java

@@ -0,0 +1,14 @@
+package com.ankurm.junitmigration;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+/** A JUnit 4 test. It is discovered by the Vintage engine, not by Jupiter. */
+public class LegacyJUnit4Test {
+
+    @Test
+    public void stillRuns() {
+        assertEquals(4, 2 + 2);
+    }
+}