Add error tests

See f0193f20

tests/CoreTests/Errors.swift

+// Copyright (c) 2016 Drew Crawford.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import CarolineCore
+class NoErrorCheck: CarolineTest {
+    func test() {
+        self.check {
+            print("got here")
+        }
+    }
+}
+
+private struct MyError: Error {
+
+}
+
+class ErrorCheck: CarolineTest {
+    func test() {
+        self.check {
+            throw MyError()
+        }
+    }
+    var expectFailure: Bool { return true }
+}
+