Throw more informative exception when relationship is missing

1 files changed, 15 insertions, 0 deletions

diff --git a/src/test/java/org/zwobble/mammoth/tests/util/MammothAsserts.java b/src/test/java/org/zwobble/mammoth/tests/util/MammothAsserts.java
new file mode 100644
index 0000000..2439ee2
--- /dev/null
+++ b/src/test/java/org/zwobble/mammoth/tests/util/MammothAsserts.java
@@ -0,0 +1,15 @@
+package org.zwobble.mammoth.tests.util;
+
+import org.zwobble.mammoth.internal.util.Casts;
+
+public class MammothAsserts {
+    public static <T extends Throwable> T assertThrows(Class<T> exceptionType, Action action) throws T {
+        try {
+            action.run();
+            throw new AssertionError("Expected exception");
+        } catch (RuntimeException exception) {
+            return Casts.tryCast(exceptionType, exception)
+                .orElseThrow(() -> exception);
+        }
+    }
+}