add assertThrows testing utility function

This is much easier to use than built-in JUnit method-level checks.

2 files changed, 44 insertions, 0 deletions

diff --git a/test/junit/scala/tools/testing/AssertThrowsTest.scala b/test/junit/scala/tools/testing/AssertThrowsTest.scala
new file mode 100644
index 0000000000..ecc46244bd
--- /dev/null
+++ b/test/junit/scala/tools/testing/AssertThrowsTest.scala
@@ -0,0 +1,25 @@
+package scala.tools
+package testing
+
+import org.junit.Assert._
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.junit.runners.JUnit4
+import AssertUtil.assertThrows
+
+@RunWith(classOf[JUnit4])
+class AssertThrowsTest {
+  class Foo extends Exception
+  class Bar extends Exception
+
+  @Test
+  def catchFoo = assertThrows[Foo] { throw new Foo }
+
+  @Test
+  def rethrowBar =
+    try assertThrows[Foo] { throw new Bar }
+    catch {
+      case bar: Bar =>
+      case e: Throwable => fail(s"expected Bar but got $e")
+    }
+}
\ No newline at end of file
diff --git a/test/junit/scala/tools/testing/AssertUtil.scala b/test/junit/scala/tools/testing/AssertUtil.scala
new file mode 100644
index 0000000000..9efa9327a7
--- /dev/null
+++ b/test/junit/scala/tools/testing/AssertUtil.scala
@@ -0,0 +1,19 @@
+package scala.tools
+package testing
+
+/** This module contains additional higher-level assert statements
+ *  that are ultimately based on junit.Assert primitives.
+ */
+object AssertUtil {
+  /** Check if exception T was thrawn during evaluation of f. If any
+   *  other exception or throwable is found instead it will be re-thrown.
+   */
+  def assertThrows[T <: Exception](f: => Any)(implicit manifest: Manifest[T]): Unit =
+    try f
+    catch {
+      case e: Exception =>
+        val clazz = manifest.erasure.asInstanceOf[Class[T]]
+        if (!clazz.isAssignableFrom(e.getClass))
+          throw e
+    }
+}
\ No newline at end of file