Make our own assertThrows()

Author: eregon

src/test/java/org/truffleruby/ArrayStoreTest.java

@@ -12,7 +12,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
-import static org.junit.Assert.fail;
+import static org.truffleruby.RubyTest.assertThrows;
 
 import org.junit.Test;
 import org.truffleruby.core.array.library.ArrayStoreLibrary;
@@ -32,12 +32,9 @@ public void delegatedArrayLibraryOnlyAcceptsSpecificStore() {
         assertFalse(library.accepts(longDelegated));
 
         assertEquals(42, library.read(intDelegated, 0));
-        try {
-            library.read(longDelegated, 0);
-            fail();
-        } catch (AssertionError e) {
-            assertTrue(e.getMessage().contains("Library does not accept given receiver"));
-        }
+
+        var e = assertThrows(() -> library.read(longDelegated, 0), AssertionError.class);
+        assertTrue(e.getMessage().contains("Library does not accept given receiver"));
     }
 
     @Test
@@ -51,12 +48,9 @@ public void sharedArrayLibraryOnlyAcceptsSpecificStore() {
         assertFalse(library.accepts(longShared));
 
         assertEquals(42, library.read(intShared, 0));
-        try {
-            library.read(longShared, 0);
-            fail();
-        } catch (AssertionError e) {
-            assertTrue(e.getMessage().contains("Library does not accept given receiver"));
-        }
+
+        var e = assertThrows(() -> library.read(longShared, 0), AssertionError.class);
+        assertTrue(e.getMessage().contains("Library does not accept given receiver"));
     }
 
     @Test

src/test/java/org/truffleruby/RubyTest.java

@@ -34,13 +34,23 @@
 public abstract class RubyTest {
 
     public static void assertThrows(Runnable test, Consumer<PolyglotException> exceptionVerifier) {
+        PolyglotException e = assertThrows(test, PolyglotException.class);
+        assertTrue(e.isGuestException());
+        exceptionVerifier.accept(e);
+    }
+
+    public static <E> E assertThrows(Runnable test, Class<E> exceptionClass) {
         try {
             test.run();
-            fail("should have thrown");
-        } catch (PolyglotException e) {
-            assertTrue(e.isGuestException());
-            exceptionVerifier.accept(e);
+        } catch (Throwable e) {
+            if (!exceptionClass.isInstance(e)) {
+                throw e;
+            }
+            return exceptionClass.cast(e);
         }
+
+        fail("should have thrown");
+        throw new Error("unreachable");
     }
 
     public static <T extends Node> T adopt(T node) {