Cover trimming boundaries

Author: mpkorstanje

jupiter-tests/src/test/java/org/junit/jupiter/api/AssertionFailureBuilderTest.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2015-2025 the original author or authors.
+ *
+ * All rights reserved. This program and the accompanying materials are
+ * made available under the terms of the Eclipse Public License v2.0 which
+ * accompanies this distribution and is available at
+ *
+ * https://www.eclipse.org/legal/epl-v20.html
+ */
+
+package org.junit.jupiter.api;
+
+import static java.util.concurrent.Executors.newSingleThreadExecutor;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.AssertionFailureBuilder.assertionFailure;
+import static org.junit.jupiter.api.Assertions.assertLinesMatch;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.ExecutorService;
+
+import org.opentest4j.AssertionFailedError;
+
+class AssertionFailureBuilderTest {
+
+	@Test
+	void doesNotTrimByDefault() {
+		var error = AssertionsFacade.fail();
+		assertStackTraceMatch(error,
+			"""
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:\\E.+
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest$AssertionsFacade.fail(AssertionFailureBuilderTest.java:\\E.+
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest.doesNotTrimByDefault(AssertionFailureBuilderTest.java:\\E.+
+					>>>>
+					""");
+	}
+
+	@Test
+	void trimsUpToAssertionsFacade() {
+		var error = AssertionsFacade.failWithTrimmedStacktrace(AssertionsFacade.class);
+		assertStackTraceMatch(error,
+			"""
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest.trimsUpToAssertionsFacade(AssertionFailureBuilderTest.java:\\E.+
+					>>>>
+					""");
+	}
+
+	@Test
+	void trimsUpToAssertionFailureBuilder() {
+		var error = AssertionsFacade.failWithTrimmedStacktrace(AssertionFailureBuilder.class);
+		assertStackTraceMatch(error,
+			"""
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest$AssertionsFacade.failWithTrimmedStacktrace(AssertionFailureBuilderTest.java:\\E.+
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest.trimsUpToAssertionFailureBuilder(AssertionFailureBuilderTest.java:\\E.+
+					>>>>
+					""");
+	}
+
+	@Test
+	void ignoresClassNotInStackTrace() {
+		var error = AssertionsFacade.failWithTrimmedStacktrace(String.class);
+		assertStackTraceMatch(error,
+			"""
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:\\E.+
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest$AssertionsFacade.failWithTrimmedStacktrace(AssertionFailureBuilderTest.java:\\E.+
+					\\Qorg.junit.jupiter.api.AssertionFailureBuilderTest.ignoresClassNotInStackTrace(AssertionFailureBuilderTest.java:\\E.+
+					>>>>
+					""");
+	}
+
+	@Test
+	void canTrimToEmptyStacktrace() throws ExecutionException, InterruptedException {
+		try (ExecutorService service = newSingleThreadExecutor()) {
+			// Ensure that the stacktrace starts at Thread.
+			var error = service.submit(() -> AssertionsFacade.failWithTrimmedStacktrace(Thread.class)).get();
+			assertThat(error.getStackTrace()).isEmpty();
+		}
+	}
+
+	private static void assertStackTraceMatch(AssertionFailedError assertionFailedError, String expectedLines) {
+		List<String> stackStraceAsLines = Arrays.stream(assertionFailedError.getStackTrace()) //
+				.map(StackTraceElement::toString) //
+				.toList();
+		assertLinesMatch(expectedLines.lines().toList(), stackStraceAsLines);
+	}
+
+	static class AssertionsFacade {
+		static AssertionFailedError fail() {
+			return assertionFailure().build();
+		}
+
+		static AssertionFailedError failWithTrimmedStacktrace(Class<?> testCaseClass) {
+			return assertionFailure().trimStacktrace(testCaseClass).build();
+		}
+
+	}
+}