diff --git a/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertNullAssertionsTests.java b/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertNullAssertionsTests.java
index e219e334218..54849ad6d3b 100644
--- a/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertNullAssertionsTests.java
+++ b/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertNullAssertionsTests.java
@@ -11,8 +11,8 @@
 package org.junit.jupiter.api;
 
 import static org.junit.jupiter.api.AssertionTestUtils.assertExpectedAndActualValues;
-import static org.junit.jupiter.api.AssertionTestUtils.assertMessageEndsWith;
-import static org.junit.jupiter.api.AssertionTestUtils.assertMessageStartsWith;
+import static org.junit.jupiter.api.AssertionTestUtils.assertMessageEquals;
+import static org.junit.jupiter.api.AssertionTestUtils.assertMessageMatches;
 import static org.junit.jupiter.api.AssertionTestUtils.expectAssertionFailedError;
 import static org.junit.jupiter.api.Assertions.assertNull;
 
@@ -46,7 +46,7 @@ void assertNullWithNonNullObject() {
 			expectAssertionFailedError();
 		}
 		catch (AssertionFailedError ex) {
-			assertMessageEndsWith(ex, "expected: <null> but was: <foo>");
+			assertMessageEquals(ex, "expected: <null> but was: <foo>");
 			assertExpectedAndActualValues(ex, null, "foo");
 		}
 	}
@@ -76,8 +76,7 @@ private void assertNullWithNonNullObjectWithNullStringReturnedFromToString(Suppl
 			// Should look something like:
 			// expected: <null> but was: java.lang.String@264b3504<null>
 			String prefix = (messageSupplier != null ? messageSupplier.get() + " ==> " : "");
-			assertMessageStartsWith(ex, prefix + "expected: <null> but was: java.lang.String@");
-			assertMessageEndsWith(ex, "<null>");
+			assertMessageMatches(ex, prefix + "expected: <null> but was: java\\.lang\\.String@.+<null>");
 			assertExpectedAndActualValues(ex, null, actual);
 		}
 	}
@@ -107,9 +106,8 @@ private void assertNullWithNonNullObjectWithNullReferenceReturnedFromToString(Su
 			// Should look something like:
 			// expected: <null> but was: org.junit.jupiter.api.AssertNullAssertionsTests$NullToString@4e7912d8<null>
 			String prefix = (messageSupplier != null ? messageSupplier.get() + " ==> " : "");
-			assertMessageStartsWith(ex,
-				prefix + "expected: <null> but was: org.junit.jupiter.api.AssertNullAssertionsTests$NullToString@");
-			assertMessageEndsWith(ex, "<null>");
+			assertMessageMatches(ex, prefix
+					+ "expected: <null> but was: org\\.junit\\.jupiter\\.api\\.AssertNullAssertionsTests\\$NullToString@.+<null>");
 			assertExpectedAndActualValues(ex, null, actual);
 		}
 	}
@@ -121,8 +119,7 @@ void assertNullWithNonNullObjectAndMessage() {
 			expectAssertionFailedError();
 		}
 		catch (AssertionFailedError ex) {
-			assertMessageStartsWith(ex, "a message");
-			assertMessageEndsWith(ex, "expected: <null> but was: <foo>");
+			assertMessageEquals(ex, "a message ==> expected: <null> but was: <foo>");
 			assertExpectedAndActualValues(ex, null, "foo");
 		}
 	}
@@ -134,8 +131,7 @@ void assertNullWithNonNullObjectAndMessageSupplier() {
 			expectAssertionFailedError();
 		}
 		catch (AssertionFailedError ex) {
-			assertMessageStartsWith(ex, "test");
-			assertMessageEndsWith(ex, "expected: <null> but was: <foo>");
+			assertMessageEquals(ex, "test ==> expected: <null> but was: <foo>");
 			assertExpectedAndActualValues(ex, null, "foo");
 		}
 	}
diff --git a/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertionTestUtils.java b/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertionTestUtils.java
index a95c27212ab..a2cd16f6629 100644
--- a/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertionTestUtils.java
+++ b/junit-jupiter-engine/src/test/java/org/junit/jupiter/api/AssertionTestUtils.java
@@ -38,6 +38,13 @@ static void assertMessageEquals(Throwable ex, String msg) throws AssertionError
 		}
 	}
 
+	static void assertMessageMatches(Throwable ex, String regex) throws AssertionError {
+		if (!ex.getMessage().matches(regex)) {
+			throw new AssertionError("Exception message should match regular expression [" + regex + "], but was ["
+					+ ex.getMessage() + "].");
+		}
+	}
+
 	static void assertMessageStartsWith(Throwable ex, String msg) throws AssertionError {
 		if (!ex.getMessage().startsWith(msg)) {
 			throw new AssertionError(